I TNG NGHIN CU

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Tham gia bin son

GVC.ThS. Trn Vn Hng

GVC.ThS. L Vn An

GVC.TS. Trn nh Bnh

GVC.ThS. Trn Th Nh Hoa

GV.ThS. Ng Vit Qunh Trm

MC LC

Trang

Phn I: i cng vi sinh y hc

1

i tng nghin cu v lch s pht trin ca vi sinh vt hc 1

Hnh th, cu to v sinh l ca vi khun 5

Di truyn vi khun 12

Anh hng ca cc nhn t ngoi cnh n s pht trin ca vi sinh vt 17

Tit trng, kh trng v khng sinh 23

i cng virus 30

Bacteriophage 39

Phng nga v iu tr bnh virus 42

Nhim trng v c lc ca vi sinh vt 49

Khng nguyn vi sinh vt 54

S khng ca c th chng li cc vi sinh vt gy bnh 57

K thut min dch s dng trong chn on vi sinh vt 62

Vacxin v huyt thanh 68

Vi sinh vt trong t nhin v k sinh ngi.Cc ng truyn bnh 78

Nhim trng bnh vin 83

Phn II: Cc vi khun gy bnh thng gp

88

Cc cu khun gy bnh 88

H vi khun ng rut (Enterobacteriaceae) 97

Vi khun dch hch v Legionella pneumophila 108

Haemophilus v Bordetella 113

Trc khun m xanh v Burkholderia pseudomallei 117

Vibrio 121

Campylobacter v Helicobacter 125

Cc xon khun gy bnh 128

Vi khun bch hu 135

Trc khun than v Listeria monocytogenes 139

Cc Clostridia gy bnh 142

H Mycobacteriaceae 148

Rickettsia, Chlamydia v Mycoplasma 153

Phn III: Cc virus gy bnh thng gp

160

Cc virus h Herpesviridae 160

Adenovirus 167

Enterovirus 170

Rotavirus

174

Virus cm 177

Paramyxoviridae 181

Flaviviridae 185

Virus di 190

Cc virus sinh khi u 193

Cc virus vim gan 197

Virus HIV/AIDS 206

Cc virus gy bnh khc

212

PHN I

I CNG VI SINH Y HC

I TNG NGHIN CU

V LCH S PHT TRIN CA VI SINH VT HC

Mc tiu hc tp1. Trnh by c i tng nghin cu ca vi sinh vt hc.

2. Trnh by c lch s pht trin ca vi sinh vt hc v hng gii quyt bnh nhim trng hin nay.

I. i tng NGHIN CU ca vi sinh VT hc

Vi sinh vt hc (Microbiology) l khoa hc kho st hot ng ca cc vi sinh vt (t Hylp micros l nh b, bios l s sng v logos l khoa hc).

Vi sinh vt l cc sinh vt nh b mt trn khng thy v ch c pht hin bng knh hin vi.

Mun o kch thc ca vi sinh vt, ngi ta s dng cc n v sau:

Micromet ((m, micrometre) = 10-6m

Nanomet (nm, nanometre) = 10-9m

Angstrom

= 10-10m

Vi sinh vt bao gm vi khun, nm men, nm mc, to, nguyn sinh ng vt v virus. Trc khi khm ph vi sinh vt ngi ta chia sinh vt lm hai gii: gii ng vt v gii thc vt. Sau khi khm ph vi sinh vt ngi ta nhn thy vi sinh vt kt hp nhng c tnh ca thc vt v ng vt vi tt c nhng t hp c th c, cho nn vic phn loi sinh vt thnh hai gii lm pht sinh mt s iu khng hp l. V d nh nm men c phn loi l thc vt v phn ln khng di ng mc d chng t c nhng tnh cht ca thc vt v cho thy nhng lin h sinh tin ha m nt vi nguyn sinh ng vt.

Nm 1866 nh khoa hc c E. Haeckel ngh xp vi sinh vt vo mt gii ring, gii Nguyn sinh (Protista). Gii ny phn bit vi thc vt v ng vt s t chc n gin ca chng: d n bo hoc a bo, t bo ca chng khng bit ha thnh m.

Nm 1969 nh sinh thi hc M R.H. Whittaker xut h thng phn loi nm gii: l gii Khi sinh (Prokaryota hay Monera) bao gm vi khun v vi khun lam, gii Nguyn sinh (Protista), gii Nm (Fungi), gii Thc vt (Plantae) v gii ng vt (Animalia).Theo kin ngh ca nh sinh vt hc Trung Quc Trn Th Tng nm 1979 th nhm gii sinh vt nhn tht bao gm gii Thc vt, gii Nm v gii ng vt, nhm gii sinh vt nhn nguyn thu bao gm gii Vi khun v gii Vi khun lam, cn gii Virus thuc v nhm gii sinh vt cha c t bo.

Theo quan im hin i (P.H. Raven, G.B. Johnson, 2002) th mi sinh vt trn th gii thuc v 6 gii khc nhau: gii C khun (Archaebacteria), gii Vi khun (Eubacteria), gii Nguyn sinh (Protista), gii Nm (Fungi), gii Thc vt (Plantae) v gii ng vt (Animalia).

Phn ln vi sinh vt nm trong 4 gii: C khun, Vi khun, Nguyn sinh v Nm ca h thng 6 gii ni trn.

T bo nhn tht c nhn cha mt s i nhim sc th, mng nhn ni lin vi li ni cht nguyn sinh. Nguyn tng ca t bo nhn tht c li ni cht nguyn sinh, khng bo v nhng plastit t sao chp. Nhng plastit cha ADN ring v nhn ln bng phn lit. Nhng plastit bao gm ti lp th cha h thng chuyn ch in t ca s phosphoryl ha v lc lp nhng sinh vt quang hp cha lc dip t v nhng thnh phn quang hp khc. Nguyn tng bn cht lipoprotein nm bn trong mng t bo. Nhiu vi sinh vt t bo nhn tht c vch t bo to nn bi celluloza, chitin hoc oxyt silic.T bo nhn tht c th di ng nh nhng lng. Nhng lng ny gm mt b 9 si nh bao quanh 2 si nh trung tm.

T bo nhn nguyn thu (T bo nhn s) c cu trc t bo n gin. Nhn ch gm c mt nhim sc th khng mng nhn, nhng vch t bo li phc tp hn. T bo nhn nguyn thu khng c plastit t sao chp nh ti lp th v lc lp. Enzyme cytochrom c tm thy mng t bo; nhng c th quang hp, nhng sc t quang hp c tm thy nhng phin mng nm di mng t bo. Vi khun thng tch t vt liu d tr di hnh thc nhng ht nh khng ha tan, dng polyme, trung tnh, tr thm thu. Vt liu cacbon c bin i bi mt s vi khun thnh polyme polyaxit-(- hydrobutyric v bi nhng vi khun khc thnh polyme glucoza tng t nh glycogen gi l granuloza. Nhng ht nh d tr c s dng nh ngun C lc s tng hp protein v axit nucleic c thc hin tr li. Mt cch tng t mt vi vi khun oxy ha sulfua bin i lng tha H2S mi trng bn ngoi thnh nhng ht sulfua ni bo. Nhiu vi khun tch tr pht pht hu c thnh nhng ht nh polymemetaphosphate gi l volutin.

Virus khc vi tt c cc c th c t bo k c vi khun v Rickettsia. Virion hay l ht virus gm mt phn t ADN hoc ARN nm bn trong mt v protein gi l capsid. Vo bn trong t bo vt ch, axit nucleic ca virus s dng b my tng hp ca t bo hnh thnh axit nucleic v nhng thnh phn khc ca virus. Axit nucleic v nhng thnh phn protein c hiu kt hp thnh ht virus xm nhim hon chnh gi l virion. Virion c phng thch vo mi trng bn ngoi v bt u qu trnh xm nhim t bo vt ch.

II. S LC Lch s pht trin ca vi sinh vt hc

1. S pht hin vi sinh vt

S pht hin vi sinh vt gn lin vi s pht minh knh hin vi. Anton van Leeuwenhoek (1632 - 1723) ngi H Lan, l ngi u tin th k XVII nhn thy vi sinh vt nh nhng knh hin vi phng i 270 - 300 ln m ng ch to (1676). Do s hn ch v phng i v phn gii ca knh hin vi cho nn nhng nghin cu hin vi ca c th sng rt b hn ch v mi n u th k XIX chic knh hin vi hon chnh u tin mi ra i v t cho n nay con ngi ln lt sng to ra hng lot cc loi knh hin vi quang hc khc nhau th nhiu s kin quan trng mi c pht hin.2. S trng thnh ca vi sinh vt hc

Trong th k XVII v sut th k XVIII vi sinh vt hc ch ch trng v phn m t, tuy nhin cng c mt s cng trnh xut sc nh Spallanzani s dng mi trng nui cy kh khun bng nhit, Edward Jenner pht minh vaccine u ma, Zinke pht hin tc nhn ca bnh di trong nc bt ca ch b di.

Th k XIX mi cho thy nhng bc pht trin ln v vi sinh vt hc nh cng lao ca Louis Pasteur v Robert Koch.

L.Pasteur (1822 - 1895) hon chnh vic nghin cu vi sinh vt. Vi sinh vt khng nhng c m t chnh xc m cn c kho st y v nhng tnh cht sinh l.

L.Pasteur l nh vi sinh vt hc v i c cng:

- Chm dt tranh lun v thuyt t sinh bng cc th nghim xut sc vi bnh c ngng.

- Pht hin tc nhn ca s ln men nh ln men ru, ln men thi l vi sinh vt: cc vi sinh vt pht trin to thnh cc enzyme chu trch nhim v hin tng ln men.

- Xc nh vai tr tc nhn gy bnh ca cc vi sinh vt trong bnh nhim trng

- Khi qut ha vn vaccine v tm ra phng php iu ch mt s vaccine phng bnh nh vaccine bnh than, vaccine bnh t g... v pht minh vaccine di.

R.Koch (1843 - 1910) cng ng gp ln lao cho vi sinh vt hc nh nhng cng trnh:

- Pht trin nhng k thut c nh v nhum vi khun.

- S dng mi trng c phn lp vi khun rng.

- Nu tiu chun xc nh bnh nhim trng.

- Khm ph vi khun lao, vi khun t.

Nh cng lao ca L.Pasteur, R.Koch v nhiu nh bc hc khc, phn ln cc vi khun gy bnh ngi v ng vt u c khm ph u th k XX. Lc by gi vi sinh hc tr thnh mt khoa hc ng dng quan trng trong lnh vc y hc, nng nghip v cng nghip.

Trong lm sng, khoa ly thnh lp tip nhn bnh nhn nhim trng, khoa ngoi s dng phng php phu thut st trng, tin ca phng php phu thut v trng ngy nay.

3. Nhng thnh tu hin i

Trong nhng thp k gn y t mt khoa hc ng dng, vi sinh vt hc tr thnh mt khoa hc c bn lm pht sinh mt ngnh khoa hc mi: sinh hc phn t v di phn t v cng vi cc ngnh khoa hc khc to nn mt cuc cch mng khoa hc k thut hin i.

Nh nhng hiu bit v di truyn hc hin i m m hnh nghin cu l E.coli, Watson v Crick pht hin mu cu trc ca ADN v c ch sao chp bn bo tn lm c s cho s hnh thnh sinh hc phn t v di phn t. Nhng pht hin k diu v c cu ca m di truyn v cc cu trc khc ca t bo sng c s dng lm c s cho s pht trin cng nghip sinh hc, ngnh cng nghip cho php con ngi can thip vo qu trnh hnh thnh v pht trin ca sinh vt phc v li ch ca con ngi .

Gn y nhng k thut tng hp gen, tho ghp gen lm cho cng ngh sinh hc tr thnh mt lc lng sn xut mi nhn ca nn kinh t th gii. Trong lnh vc y hc nhng k thut trn c nhiu trin vng gii quyt cc bnh di truyn, phng chng cc bnh nhim trng, bnh ung th .

III. nhng Vn hin nay ca vi sinh vt y hc

Trong y hc, vi sinh vt l cn nguyn ca cc bnh nhim trng. V vy khi xt v tm quan trng hin nay ca vi sinh vt y hc phi cp ti tnh hnh cc bnh nhim trng.

T ngn xa bnh nhim trng l mt tai ha cho nhn loi. Bnh u ma, bnh dch hch, bnh dch t ... git cht hng triu ngi, tn ph nhiu lng mc, thnh ph.

T khi vi sinh vt hc trng thnh cho n nay con ngi c kh nng dn dn ch ng c bnh nhim trng. Nhng con ng ch ng tin ti xa b bnh nhim trng l con ng kh khn v lu di.

Thnh tu vang di u tin xy ra vo nm 1891 lc Von Behring cu sng mt em b nh huyt thanh khng bch hu, m u thi k huyt thanh liu php. Thc t cho thy huyt thanh liu php c nhng mt hn ch v ch hu hiu i vi nhng bnh nhim c t vi khun nh bch hu, un vn, hoi th sinh hi .v.v...

Thnh tu vang di th hai l cng lao ca G.Domagk pht minh sulfonamit nm 1935. Nhng dn dn v kh sulfonamit t ra yu km khng kh nng iu tr phn ln cc bnh nhim trng thng gp.

Nm 1940 Fleming, Florey v Chain pht minh penicillin v a vo iu tr m u thi i khng sinh. Trong sut hai thp k, nhiu khng sinh hu hiu c pht minh v ngi ta c th ch ng mt cch hu hiu cc bnh nhim trng. Nhng thi gian cho thy bnh nhim trng vn cn lu mi gii quyt xong v cc vi khun khng thuc c quan st trong cc loi vi khun. May mn l cc khng sinh hu hiu mi khm ph gi khng cho cc vi khun khng thuc pht trin quy m qu ln khng ch ng c. u thp k 80, thc t cho thy cc vi khun khng thuc xut hin ngy cng nhiu nhng cc khng sinh hu hiu mi khm ph tr nn him dn. Tr nhng khng sinh thuc nhm quinolon, nhng khng sinh c gi l mi ch l s xp xp li hay l s thay i cu trc phn t ca nhng khng sinh khm ph t trc bng k thut bn tng hp hoc tng hp.

Hin nay, phn ln cc bnh nhim trng c ch ng mt cch hu hiu, cc v dch c dp tt nhanh chng nhng vn cn nghin cu nhiu ch ng cc vi khun khng thuc v tm cc thuc hu hiu iu tr cc bnh virus.

Hng gii quyt bnh nhim trng hin nay c th l s dng ng thi ba bin php sau:

- Thc hin mt chin lc khng sinh hn ch cc vi khun khng thuc.

- Tip tc tm kim cc khng sinh hu hiu mi iu tr bnh vi khun v pht minh cc thuc khng virus hu hiu.

- iu ch cc vaccine hu hiu bng cc k thut hin i nh cng ngh gen phng nga cc bnh nhim trng, dn dn tin n xa b chng nh trng hp bnh u ma trn phm vi ton th gii.HNH TH , CU TO V SINH L CA VI KHUN

Mc tiu hc tp1. M t c cc loi hnh th ca vi khun

2. M t c cu trc ca t bo vi khun

3. Trnh by c cc nt c bn ca sinh l vi khun

I. HNH TH CA VI KHUN

Vi khun thng thng c hnh th nht nh do vch t bo xc nh. Mt s khng vch ( hnh thc L) nh Mycoplasma khng c hnh th nht nh. ng knh trung bnh ca vi khun khang 1(m . Nhng i din nh nht nh Mycoplasma c ng knh khang 0,1(m v nhng i din ln hn c kch thc hng chc (m nh Spirilium volutans 20(m. Cc vi khun gy bnh c kch thc t 0,2(m n 10(m

V hnh th ngi ta c th chia vi khun thnh cu khun, trc khun v vi khun hnh xon.

1. Cu khun :

L nhng vi khun hnh cu, hnh trng hay hnh ht c ph

1.1. Micrococci (n cu)

y l nhng cu khun xp hng u hoc khng u, l nhng tp khun tm thy trong khng kh v nc.

1.2. Diplococci (Song cu)

L nhng cu khun xp tng i phn chia trong mt mt phng. Mt s gy bnh cho ngi nh ph cu, lu cu, cu khun mng no.

1.3. Stretococci (Lin cu):

L nhng cu khun xp thnh chui ngn hoc di. Mt s lai gy bnh cho ngi nh Streptococcus pyogenes thuc nhm A ca Lancefield.

1.4. Tetracocci (T cu)

Cc cu khun hp thnh 4, phn chia theo hai mt phng, rt t khi gy bnh.

1.5. Sarcina (Bt cu)

Cc cu khun xp thnh 8-16 con, phn chia theo ba mt phng, thng tm thy trong khng kh.

1.6. Staphylococci (T cu)

Cc cu khun hp thnh m nh chm nho, phn chia theo mt phng, mt s loi gy bnh cho ngi v thng pht trin nhanh chng tnh khng vi nhiu khng sinh.

2. Trc khun

L nhng vi khun c hnh que thng.

2.1.Bacteria L nhng trc khun hiu kh, khng to nha bo nh vi khun ng mt, vi khun bch cu, vi khun lao...

2.2. BacilliL nhng trc khun hiu kh tuyt i to nha bo v d trc khun bnh than.

2.3.ClostridiaL nhng trc khun k kh Gram dng to nha bo, v d trc khun un vn, trc khun ng c tht.

3. Vi khun hnh xon

3.1. Phy khunCh c mt phn ca hnh xon nn c hnh du phy, v d phy khun t.

3.2.Xon khunC nhiu vng xon, v d xon khun giang mai, Leptospira, Borrelia.

II. CU TO CA T BO VI KHUN

Khc vi cc thnh vin ca protista lp trn c nhn tht nh t bo ng vt v thc vt, vi khun c t bo nhn s, nhn ch c mt nhim sc th, khng c mng nhn, khng c ti lp th, khng c b my phn bo nhng cc t bo li phc tp hn.

1. Vch t bo

S hin din ca vch t bo vi khun c pht hin bng hin tung ly tng, bng cch nhum v bng phn lp trc tip.

Tc dng c hc nh siu m phi hp vi ly tm cho php thu hoch vch t bo rng, tch ri khi nguyn tng.

1.1.Vch t bo vi khun gram dng

Knh hin vi in t cho thy vch t bo dy t 15 n 50 nm. Thnh phn ch yu l mucopeptit gi l murein, mt cht trng hp m nhng n v ho hc l nhng ng amin. N-acetyl glucosamin v axt N-acetyl muramic v nhng chui peptit ngn cha alanin, axt glutamic v axt diaminopimelic hoc lysin. Ngoi ra vch t bo ca mt s vi khun gram dng cn cha axt teichoic. mt vi lai vi khun, axt teichoic chim ti 30% trng lng kh ca vch t bo.

1.2. Vch t bo vi khun Gram m gm ba lp

Lp mucopeptit mng hn khang 10nm v hai lp lipoprotein v lipopolysaccharide bn ngoi, lp lipoprotein cha tt c nhng axt amin thng thng. Khng c axt teichoic, vch t bo vi khun gram m cha mt lng lipit ng k, khong 20 % trng lng kh ca vch t bo.

1.3.Chc nng ca vch t bo

Vch t bo vi khun c nhiu chc nng:

- Duy tr hnh th ca vi khun: Vch cng to nn b khung, lm cho vi khun c hnh th nht nh .

- Quyt nh tnh bt mu gram ca vi khun: S bt mu gram khc nhau vi khun gram dng v gram m l do tnh thm thu khc nhau i vi cn ca hai nhm vi khun . Nu dng lysozym bin i vi khun gram dng thnh protoplast khng c vch th protoplast li bt mu gram m.

- To nn khng nguyn thn O ca vi khun ng rut: iu ch khng nguyn 0 ca vi khun ng rut x l vi khun khng di ng bng nhit v cn.

- To nn ni c t ca vi khun ng rut. Ni c t ch c gii ta lc vi khun b li gii. vi khun ng rut, ni c t l nhng phc hp lipopoly-saccarit dn xut t vch t bo.

2. Mng nguyn tng

L mng bn thm dy khong 10nm nm st vch t bo. Ngi ta c th chng minh s hin din ca n bng hin tng ly tng hoc nhum vi xanh Victoria 4R. N cha 60-70% lipit, 20-30% protein v mt lng nh hydrat cacbon. Mng nguyn tng c chc nng ro cn thm thu ca t bo, ngn cn khng cho nhiu phm vt vo bn trong t bo nhng li xc tc vic chuyn ch hat ng ca nhiu phm vt khc vo bn trong t bo. Hn na mng t bo cha nhiu h thng enzyme v v vy c chc nng ging nh ti lp th ca ng vt v thc vt. Mng nguyn tng cho thy nhng ch lm vo gi l mc th. vi khun Gram dng mc th kh pht trin cho thy hnh nh nhiu l ng tm. vi khun Gram m mc th ch l vt nhn n gin.

3. Nguyn tng

L cu trc c bao bc bn ngoi bi mng nguyn tng, trng th gel, cu trc ny gm 80% nc, cc protein c tnh cht enzyme, cacbohydrat, lipid v cc ion v c nng cao, v cc hp cht c trng lng phn t thp. Nguyn tng cha dy c nhng ht hnh cu ng knh 18nm gi l ribsm. Ngoi ra cn c th tm thy nhng ht d tr glycogen, granulosa hoc polymetaphotphat.

4. Nhn t bo

C th thy vi knh hin vi nh sng sau khi nhum hoc soi trc tip knh hin vi pha tng phn. Nhn c th hnh cu, hnh que, hnh qu t hoc hnh ch V. Kho st knh hin vi in t nhn khng c mng nhn v b my phn bo. N l mt si DNA trng lng phn t 3x109 dallon v cha mt nhim sc th duy nht di khong 1mm nu khng xon. Nhn ni lin mt u vi th mc. S ni lin ny gi mt vai tr ch yu trong s tch ri 2 nhim sc th con sau khi si nhim sc th m tch i. Trong s phn chia nhn hai mc th qua ch ni lin vi mng nguyn tng di chuyn theo nhng hng i nghch theo hai nhm con ni lin vi chng. Nh th mng nguyn tng t ng nh mt b my th s ca s gin phn vi mc th m nhn vai tr thai v sc.

5. Lng ca vi khun

Lng chu trch nhim v tnh di ng ca vi khun. Ngi ta quan st s di ng ca vi khun knh hin vi nhn git treo hoc t mt git vi khun lam knh v ph mt l knh mng. Lng di 3-12 (m hnh si gn sng, mnh 10- 20nm ) nn phi nhum vi axt tannic to thnh mt lp kt ta lm dy lng d pht hin. Lng pht xut t th y ngay bn di mng nguyn tng v c chuyn ng xoay trn. Bn cht protein n to nn do s tp hp nhng n v ph gi l flagellin to thnh mt cu trc hnh tr rng. Cch thc mc lng l mt c tnh di truyn. mt s loi nhiu lng mc quanh thn, mt s lai mt lng mc cc v mt s loi khc mt chm lng mt cc. Nu lng b lm mt i bng c hc th lng mi c to thnh nhanh chng. Lng ng vai tr khng nguyn nh khng nguyn H vi khun ng rut.

6. Pili

L nhng ph b hnh si, mm mi hn lng, mnh hn nhiu v c xu hng thng ng knh 2-3 nm v di t 0,3-1nm, tm thy t mt n hng trm mt ngoi vi khun, bn cht protein. Pili pht xut trong mng nguyn tng v xuyn qua vch t bo. Pili c tm thy vi khun gram m nhng cng c th tm thy mt s vi khun gram dng. Pili F c nhim v trong s tip hp. Nhng pili khc gip cho vi khun bm vo nim mc hoc b mt khc ca t bo.

7. V ca vi khun

V l mt cu trc nhy bc quanh vch t bo ca mt s vi khun, thng l polysaccharide, ch c v ca B.anthracis l mt polypeptide acid D-glutamic. V c th pht hin d dng huyn dch mc tu, n hin ra nh mt vng sng gia mi trng m c v t bo vi khun trng r hn. Cng c th pht hin bng phn ng phnh v hoc bng k thut nhum c bit. S t bin to thnh v rt d nhn bit v t bo c v to nn khun lc bng lng hoc nhy M trong khi t bo khng v to nn khun lc x x R. Nhim v duy nht c bit ca v l bo v vi khun chng thc bo v chng virut mun gn vo vch t bo .

8. Nha bo

Nhng thnh vin ca Bacillus, Clostridium v Sporosarcina to thnh ni nha bo di nh hng ca mi trng bn ngoi khng thun li, mi t bo lm pht sinh mt nha bo. Nha bo c th nm gia, u nt hoc gn u nt ty theo loi, vch nha bo cha nhng thnh phn mucopeptide v axt dipicolinic. S d khng ca nha bo vi ha cht c l do tnh khng thm thu ca vch nha bo, s khng vi nhit lin h n trng thi mt nc cao. V chu ng vi iu kin khng thn li bn ngoi nha bo gp phn quan trng trong kh nng ly bnh ca trc khun hiu kh to nha bo nh trc khun than hoc trc khun k kh to nha bo nh Clostridia, nht l trc khun un vn, hoi th, sinh hi, ng c tht.

III. SINH L VI KHUN

Nh cc sinh vt khc vi khun cng dinh dng, chuyn hoa v pht trin.

1. S dinh dng

pht trin vi khun i hi mi trng nui cy cha y nhng yu t dinh dng bao gm nhng hp cht cn thit cung cp nng lng v nhng hp cht c dng lm nguyn liu tng hp nhng vt liu mi ca t bo. V nguyn liu tng hp, vi khun i hi nhng nhu cu v mui khong nh PO43-, K+, Mg2+ vi lng ng k, mt s ion ( nguyn t vi lng ) ch cn mt nng rt thp nh Fe2+, Zn2+, Mo2+, Ca2+, cc ion ny thng tm thy trong nc v trong cc mui khong khng tinh khit. Ngun C do thc n nng lng cung cp. Ngun N thng thng l protein hoc mt mui amoni.

Phn ln vi khun nu c cung cp y nhng yu t trn th c kh nng tng hp cc cht cu to ca t bo. Nhng mt s vi khun mt kh nng tng hp mt vi hp cht v i hi c cung cp trong mi trng nui cy. l nhng yu t pht trin; chng c chia thnh hai loi, mt loi cn c cung cp tng lng nh v m nhn chc v xc tc nh mt thnh phn ca mt enzyme v d vitamin B, mt loi cn c cung cp tng lng ln v c dng lm nguyn liu cu to t bo nh axit amin, purin, pyrimidin.

Ngoi ra nhng iu kin vt l nh nhit pH, p sut oxy cng nh hng n s pht trin cn c iu chnh thch hp.

2. S chuyn ha

Bao gm tt c nhng phn ng ha hc xy ra nhng t bo sng. Nh nhng phn ng nng lng c chit t mi trng v c s dng cho sinh tng hp v pht trin. Trong chuyn ha quan trng nht l s oxy ha sinh hc.

2.1. S oxy ha sinh hc

S oxy ha c nh ngha nh l s loi b in t t mt c cht km theo s loi b ion hydr tc l s loi b nguyn t hydr. V vy s oxy ha c xem nh l s vn chuyn nguyn t hydr. C cht b oxy ha c gi l cht cho hydr v phm vt b kh c gi l cht nhn hydro. Phn ln hp cht hu c mt ion hydr do loi b in t. in t khng th trng thi t do trong dung dch v khng th loi b khi mt c cht nu khng c mt cht thch hp nhn n. S vn chuyn in t l ct li ca s oxy ha v s kh.

Ty theo bn cht ca cht nhn hydro cui cng ngi ta chia s oxy ha sinh hc thnh ba hnh thc : H hp hiu kh, h hp k kh v ln men. Cht nhn hydr cui cng l oxy phn t (O2) trong s h hp hiu kh, l mt hp cht v c (nitrat, sulfat, cacbonat ) trong s h hp k kh, l mt hp cht hu c trong s ln men.

V nhu cu oxy ngi ta chia thnh :

- Vi khun hiu kh bt buc nh vi khun lao v mt vi trc khun to nha bo, nhng vi khun ny i hi oxy v thiu kh nng ln men.

- Vi khun k kh bt buc nh Clostridia, Propionibactrium, chng ch pht trin khi khng c oxy.

- Vi khun ty nh nm men, vi khun ng rut. Nhng vi khun ny c th sng khng c oxy nhng i thnh chuyn ha h hp lc c oxy.

2.2. S h hp hiu kh

Cht nhn hydr cui cng l oxy phn t. C cht thng thng l ng nhng cng c th l axt bo, axt amin. in t c chuyn t cht cho hydr n cht nhn hydr qua nhiu bc. in t ly t cht cho hydro c th u tin chuyn n mt coenzyme th nht A, A do b kh thnh AH2. Mt enzyme khc li xc tc s chuyn in t t AH2 n mt coenzyme th hai B. AH2 do c oxy ha tr li thnh A v B tr nn tr thnh BH. Qu trnh ny c th tip din qua nhiu bc to nn dy chuyn h hp in t t cht cho hydr n oxy

Hnh 1: minh ho v dy chuyn in t

Kt qu cui cng l s hnh thnh mt sn phm oxy ha, mt sn phm kh v nng lng. Nng lng pht sinh hoc c d tr trong cc dy ni sn nng lng hoc ta thnh nhit.

2.3. S h hp k kh

C cht c th l hp cht hu c nhng cng c th l cht v c. Cht nhn in t y khng phi oxy khng kh m l nitrat, sulfat, cacbonat....

2.4. S ln men

C cht l hp cht hu c nhng cht nhn in t cng l hp cht hu c. y, trong dy chuyn in t thng thng ch c NAD l cht mang in t trung gian.

Hnh 2: S chuyn in t trong s ln men

So vi s h hp, s ln men km hiu qu hn nhiu, n cung cp ATP 19 ln t hn i vi 1 mol glucoza chuyn ha. Mt vi khun pht trin vi mt lng gii hn glucoza cho thy hiu sut pht trin (trng lng kh vi khun / trng lng c cht chuyn ha) ln hn trong iu kin hiu kh so vi iu kin k kh.

3. S pht trin ca vi khun

T bo nhn ln trong s pht trin. vi khun n bo, s pht trin lm gia tng s lng vi khun mt sn phm cy. Vi khun nhn ln bng phn lit. Mt th h c nh ngha nh l s tng i t bo. Thi gian th h l khan thi gian cn thit d tng i s t bo. Thi gian th h thay i ty lai vi khun, 20 pht E.coli, 20 - 24 gi vi khun lao.

3.1. S pht trin ly tha :

V hai t bo con c th pht trin cng mt tc nh t bo m nn s t bo trong rut sn phm cy tng ln vi thi gian nh mt cp s nhn 20, 21, 22, 23.....Ngha l s pht trin ly tha.

Tc pht trin ca mt sn phm cy mt thi gian xc nh t l vi s t bo hin din thi gian . S lin h ny c th biu th di dng phng trnh sau

dN

= kN (1)

dT

Phn tch phng trnh trn ta c :

N = N0 e kt (2)

Trong N0 l s t bo thi gian 0 v N l s t bo bt k thi gian t sau . Trong phng trnh (2), k l hng s pht trin :

Gii phng trnh theo k ta c :

Ln N - Ln N0 k = (3)

t

Chuyn sang logarit thp phn

log N - log N0

k = 2,302

t2 - t1Nh vy k biu th tc logarit t nhin ca s t bo tng ln vi thi gian v c th xc nh bng th.

Hnh 3. Tc logarit t nhin ca s t bo tng ln vi thi gian.

3.2. ng biu din pht trin :

Cy vo mt mi trng lng nhng vi khun ly t mt sn phm cy trc pht trin n bo ha, ln lt xc nh s t bo trong mt 1ml v biu din logarit ca nng t bo theo thi gian th thu c ng biu din pht trin.

ng biu din gm 4 pha:

Hnh 4. ng biu din pht trin A :Pha tim n B: pha ly tha C: pha dng D: pha cht.

- Pha tim n: Biu th giai an t bo bt u thch nghi vi mi trng mi. Enzyme v cht chuyn ha trung gian c to thnh v tch ly cho n khi t n mt nng m s pht trin c th bt u tr li.

- Pha ly tha: Trong pha ny tc pht trin khng i. Tt c cc vi khun iu nhn ln vi mt tt khng i v kch thc trung bnh ca t bo cng khng i.

Hin tng ny c tip tc duy tr cho n khi mt trong hai s kin sau ny xy ra. Mt hay nhiu thc n trong mi trng b thiu ht hoc sn phm chuyn ha c tch t nhiu. i vi vi khun hiu kh thc n u tin tr nn gii hn l oxy. Lc nng t bo khong 107/ml trong trng hp vi khun hiu kh, tc vi khun gim xung nu oxy khng c cho vo mi trng bng cch khuy hoc bm khng kh. Lc nng t bo t n 4-5 x 10 9/ml tc khuch tn ca oxy khng th tho mn nhu cu ngay c mi trng thong kh v s pht trin dn dn gim tc .

- Pha dng: giai on ny s thiu ht thc n v s tch ly vt phm c lm cho s lng t bo dng li hon ton. Cc vi khun sinh sn t dn v s pht trin v khi lng cng gim dn, c mt s t bo cht nhng c b li nh s to thnh mt s t bo mi.

- Pha cht: Bt u sau mt thi gian pha ng, thi gian ny thay i theo tng loi vi khun v iu kin nui cy. Vi khun cht cng ngy cng nhiu. Thng thng sau khi t bo cht, mt s t bo tip tc sng nh thc n phng thch t nhng t bo b ly gii.

DI TRUYN VI KHUN

Mc tiu hc tp

1. Trnh by c cc c ch vn chuyn di truyn vi khun.

2. Trnh by c cc c ch di truyn tnh khng thuc vi khun.

Di truyn l s duy tr cc c im qua nhiu th h. C s vt cht ca di truyn l nhim sc th. Nhim sc th ca vi khun v d nh ca E.coli gm 5x106 i nucleotide chia thnh nhiu on gi l gen, mi gen quyt nh s tng hp mt protein c hiu. Nhng protein c hiu nh enzyme v nhng cu to khc ca t bo xc nh tt c cc tnh trng ca mt c th.

Nhim sc th chu s nhn i trc khi phn bo. Do mi t bo con nhn mt b gen tng ng vi t bo m. S nhn i ca nhim sc th l mt qu trnh chnh xc, tuy nhin mi gen c mt xc xut nh v sai st trong sao chp, do lm pht sinh t bin. t bin xy ra ngu nhin khng cn s can thip ca mi trng bn ngoi vi mt tn sut rt nh t 10-5 n 10-9.

I. S vn chuyn di truyN vi sinh vt

S tin ha ca vi sinh vt ph thuc vo s bin d v s chn lc. N din ra chm chp, lc s bin d xy ra do tch ly nhng bin d lin tip mt chng sinh vt. Qu trnh ny tr nn nhanh chng vi sinh vt nh cc vi sinh vt pht trin nhng c ch vn chuyn di truyn gia cc c th.

Vi khun vn chuyn nhng yu t di truyn qua ba c ch: bin np, ti np v tip hp.

Trong bin np, mt on ADN c vn chuyn vo t bo nhn. y l mt c ch th s ca s vn chuyn gen.

Trong ti np v tip hp, nhng plasmid c vn chuyn qua trung gian ca phage hoc qua tip xc.

Plasmid l nhng phn t ADN dng vng trn nm ngoi nhim sc th v c kh nng t sao chp. Plasmid c trng khi nh so vi nhim sc th. Hai plasmid gi l khng ph hp nu chng khng th tn ti bn vng trong cng mt t bo. Nhng plasmid F mang nhn t sinh sn F. Nhng plasmid cng tn ti trong mt vi khun vi nhn t F gi l Fi+ nu chng ngn cn s tip hp ca F, gi l Fi- trong trng hp ngc li.

1. Bin np (Transformation)

Bin np l s vn chuyn ADN ha tan ca nhim sc th t vi khun cho sang vi khun nhn. Khi t bo vi khun b v do lm tan (lysis), ADN dng vng trn ca chng thot ra mi trng thnh cc on thng vi chiu di khc nhau, c kh nng gy bin np cho cc t bo nhn khc.

Griffith nm 1928 khm ph s bin np ph cu bng th nghim sau chut nht :

- Tim vo chut ph cu sng S1 c v th chut cht v nhim khun huyt.

- Tim vo chut ph cu R1 sng khng v th chut khng cht.

- Tim vo chut ph cu S1 cht th chut khng cht.

- Tim vo chut hn hp ph cu S1 cht vi R1 sng th chut cht v nhim khun huyt. T mu chut phn lp c S1 sng c v.

Griffith cng nh cc nh khoa hc thi by gi cha hiu ngha su xa ca s kin.

Alloway nm 1933 thc hin th nghim ng nghim v phn lp c ph cu S1 hn hp ph cu S1 cht v ph cu R1 sng.

Avery, Mac-Leod, Mac-Carthy nm 1944 phn lp c nhn t bin np v xc nh l ADN. Nhng lc by gi gii khoa hc cha chp nhn ADN l cht liu di truyn. n nm 1952 lc Hershey v Chase chng minh ADN ca Phage i vo bn trong vi khun trong khi v Protein b gi bn ngoi th ADN mi c cng nhn l nhn t bin np.

S bin np c khm ph thm nhiu vi khun khc: Hemophilus, Neisseria, Streptococcus, Bacillus, Acinetobacter...

Trong bin np, t bo nhn phi trng thi sinh l c bit c gi l kh np (competence) mi c kh nng tip nhn ADN ha tan ca t bo cho. Trng thi kh np xut hin trong mt giai on nht nh ca qu trnh pht trin ca t bo vo lc t bo ang tng hp vch.

Sau khi xm nhp, phn t ADN si kp b mt endonuclease ct mng t bo thnh on ngn si n v i vo nguyn tng . on ADN si n kt i vi ADN ca t bo nhn on tng ng ri ti t hp; bng cch ADN bin np kt hp vo nhim sc th ca t bo nhn. Nhim sc th ti t hp l phn t ADN si kp ca t bo nhn trong mt on ngn ca mt si c thay th bng mt on ADN ca t bo cho.

i vi vi khun ng rut, s tip nhn i hi s bin i b mt ca t bo bng cch x l vi CaCl2 .

ngha ca s bin np:S bin np cho php kt hp vo nhim sc th vi khun ADN tng hp hoc ADN bin i invitro.

Bin np cng c s dng xc nh nhng vng rt nh trn bn di truyn ca vi khun.

Bin np c th xy ra trong thin nhin. Ngi ta chn lc vi khun ti t hp c lc tng lc tim 2 chng ph cu vo phc mc chut nht. Nh th s bin np c mt ngha dch t hc, tuy nhin s vn chuyn di truyn bng bin np khng hu hiu bng s vn chuyn di truyn bng plasmid.

2. Ti np (Transduction)

Ti np l s vn chuyn ADN t vi khun cho n vi khun nhn nh phage. Trong ti np chung, phage c th mang bt k gen no ca vi khun cho sang vi khun nhn. Trong ti np c hiu, mt phage nht nh ch mang c mt s gen nht nh ca vi khun cho sang vi khun nhn.

2.1. S ti np chung

Kiu ti np ny c Zinder v Lederberg khm ph nm 1951 lc kho st s tip hp Salmonella. Lc lai ging chng L22 v chng L2, mi chng mang mt cp tnh trng t bin khc nhau th thu c vi mt t l nh mt s t bo ti t hp mang mt cp tnh trng t bin nh t bo hoang di gc, phage P22 c tm thy trong nc lc canh khun ca 2 chng vi khun trn. Phage P22 c lc vi chng L2 nhng n ha vi chng L22. Lc cho P22 vo canh khun L2 th tt c t bo ca L2 b dung gii v phng thch phage P22 trong c mt t phage cha mt mnh ADN ca L2. Lc cho chng L22 vo dung dch phage P22 ni trn th mt s phage vn chuyn nhng gen ca L2 vo L22 v vi khun t dng nh type hoang di c pht sinh qua ti t hp.

2.2 S ti np c hiu

Nm 1954 Mores nhn thy phage n ha c th thc hin mt kiu ti np khc gi l ti np c hiu. N ch vn chuyn mt nhm gii hn gen, nhm gen c chuyn nm st ch prophage gn vo nhim sc th. S ti np c hiu vn chuyn nhng gen c hiu nhim sc th v i hi s tch hp ca phage. Hn na khc vi ti np chung, phage ti np c hiu ch c phng thch lc chiu tia cc tm ch khng bao gi t tch ri khi nhim sc th.

Lc chiu tia cc tm vo mt canh khun E.coli K12 Gal+ sinh tan vi phage ( th trong nhng phage c phng thch c khong 10-6( d Gal. ( dGal l phage ( mang gen Gal nhng thiu mt dan ADN m n li trn nhim sc th ca vi khun. l phage khng hon chnh khng th nhn ln nu khng b sung on ADN b thiu nhng c th vn chuyn gen Gal. Lc cho dch dung gii ni trn vo canh khun E.coli K12 Gal- th thu c khang 10-6 vi khun ti np galactose dng tnh. l hin tng ti np tn s thp LFT (Low Frequency Transduction). Mt s t t bo trong canh khun E.coli K12 Gal- nhim dch LFT tr nn hai ln sinh tan vi phage ( bnh thng v phage ( dGal. Nhng t bo ny hnh thnh clon t bo hai ln sinh tan. Lc chiu tia cc tm vo nhng t bo ni trn th thu c mt dch phage trong nhng phage ( v phage ( dGal bng nhau. l s ti np tn s cao (High Frequency Transduction).

ngha ca s ti np:

S ti np c th cho php xc nh nhng gen rt gn nhau nhim sc th, do c s dng thit lp bn di truyn. Da vo tn s ti np hai gen cng mt lc ngi ta c th xc nh khong cch gia cc gen v nh th xc nh v tr ca chng.

Trong thin nhin s ti np gi mt vai tr c ngha trong ly lan cc plasmid khng thuc vi khun gram dng nh plasmid penicillinase t cu. Ngoi ra prophage c th em li cho vi khun mt s tnh cht c bit quan trng v d prophage ( trc khun bch hu.

3. Tip hp (Conjugation)

Tip hp l hin tng vn chuyn nhng yu t di truyn t vi khun cho (c) sang vi khun nhn (ci) khi hai vi khun tip xc vi nhau.

Lederberg v Tatum ln u tin nm 1946 pht hin ra s tip hp vi khun. Hn hp hai bin chng E.coli K12 vi nhau. Chng 1 khuyt dng vi Biotin v Methionin nhng c kh nng tng hp Threonin v Leucin k hiu B-M-T+ L+. Chng 2 khuyt dng vi Threonin v Leucin nhng tng hp c Biotin v Methionin, k hiu B+M+T- L-.

C hai bin chng ny khng mc c trong mi trng tng hp ti thiu khng cha bn cht trn nn khng to thnh khun lc.

Nu trn hai bin chng trn vi nhau ri cy vo mi trng ti thiu th thy mc cc khun lc vi tn s 10-6 . iu ny cho thy hai chng lai vi khun qua trao i gen to thnh cc t bo ti t hp c kh nng tng hp bn cht: Biotin, Methionin, Threonin, Leucin, k hiu B+, M+, T+, L+.

Hin tng tip hp lin quan n nhn t sinh sn F. Nhn t F l mt plasmid. T bo cha F l t bo c hay t bo F+ ng vai tr t bo cho. T bo khng cha F hay l t bo ci F- dng vai tr t bo nhn. Trong th nghim tip hp trn, chng (1) ng vai tr chng cho v chng (2) ng vai tr chng nhn.

T cc t bo F+, Cavalli phn lp c cc t bo Hfr (High frequency of recombination) c kh nng vn chuyn gen vi mt tn s cao. Khi lai Hfr x F- th thu c cc t bo ti t hp 1000 ln nhiu hn khi lai F+x F-.

Trong cc t bo F+ nhn t F to nn mt lc c bit gi l lc tip hp. Chnh nh lc ny m xy ra s tip hp gia cc vi khun.

Trong cc t bo Hfr nhn t F tch hp vo nhim sc th ca vi khun v ch c kh nng sao chp cng vi nhim sc th. t bo Hfr nhn t F cng to nn mt lc tip hp, nhng trong qu trnh tip hp v nm cui b gen, n y b gen vo t bo nhn qua cu nguyn tng ni lin hai t bo tip hp.

t bo Hfr trong mt s trng hp F c th tch ri khi nhim sc th v mang theo mt on ADN ca nhim sc th v c gi l F. F c kh nng t sao chp v c th vn chuyn vo t bo nhn. F c th vn chuyn mt s tnh trng ca mt vi khun ny sang mt vi khun khc. F c s dng phn lp v vn chuyn mt s gen chn lc.

Tip hp thng xy ra gia nhng vi khun cng loi nhng cng c th xy ra gia nhng vi khun khc loi nh E.coli vi Salmonella hoc Shigella nhng tn s ti t hp thp.

ngha ca s tip hp:

S tip hp l mt cng c kho st quan trng trong nhiu lnh vc sinh l v di truyn vi khun v n cho php to nn nhng vi khun phi hp nhiu t bin khc nhau.

Nh k thut tip hp ngt qung ngi ta thit lp bn nhim sc th ca vi khun. Ngoi ra chng F c s dng nghin cu hot ng ca mt s gen.

Trong thin nhin s tip hp gi mt vai tr ng k trong bin d ca vi khun c bit trong ly lan tnh khng thuc gia cc vi khun Gram m.

II. DI TRUYN V TNH KHNG THUC

Cc vi khun khng thuc c tm thy khp ni k c nhng ni cha bao gi s dng khng sinh. Ngay khi pht minh penicilin nm 1940, vi khun khng penicilin c bo co. Ngy nay vn khng thuc tr thnh mi bn tm hng u trong iu tr cc bnh nhim trng v khng sinh l mt th nghim hng ngy cc phng xt nghim vi trng.

S hnh thnh tnh khng thuc vi sinh vt l do s bin i gen nhim sc th hoc do tip nhn plasmid khng thuc.

Vi khun tr nn khng thuc qua 4 c ch: t bin, ti t hp hoc thu hoch plasmid khng thuc hoc thu hoch transposon .

1. t bin thnh khng thuc

Nhiu th nghim chng minh tnh khng thuc pht sinh do t bin, nh th tnh khng thuc lin h n s bin i gen nhim sc th v c th di truyn cho cc th h sau. S t bin xy ra vi tn sut 10-5 - 10 -9 .

Trong tnh khng thuc, khng sinh gi vai tr chn lc ch khng phi vai tr ch o. Vic s dng rng ri khng sinh lm pht trin nhanh chng cc vi khun khng thuc bng cch git cht cc vi khun nhy cm, to iu kin cho vi khun khng thuc pht sinh do t bin chim u th.

2. S ti t hp

Lc mt t bin khng thuc xut hin mt qun th vi khun th vi khun khng thuc c th vn chuyn gen khng thuc n cc vi khun nhy cm theo mt trong 3 c ch vn chuyn di truyn: bin np, ti np v tip hp ty theo loi vi khun. S ti t hp gia 2 vi khun, mi vi khun khng mt khng sinh lm xut hin nhng vi khun khng vi c 2 loi khng sinh. Trong thin nhin, s vn chuyn gen khng thuc trong ti np v tip hp xy ra vi mt tn sut thp khong 10-5. Trong bin np tn sut cha c bit, nhng c th cn thp hn na.

3. Thu hoch plasmid khng thuc

Hai c ch khng thuc trn lin quan n gen khng thuc nm trn nhim sc th. y tnh khng thuc lin h n plasmid nm ngoi nhim sc th. Plasmid khng thuc c vn chuyn theo nhng c ch khc nhau ty theo vi khun Gram dng hoc vi khun Gram m.

3.1. Plasmid khng thuc vi khun Gram m

Nm 1946 ln u tin Nht Bn ngi ta phn lp nhiu chng Shigella khng vi nhiu khng sinh : streptomycin, chloramphenicol, tetracyclin, sulfonamit. Nhn t chu trch nhim v tnh khng nhiu thuc l mt plasmid khng thuc goi l nhn t R. Nhn t R in hnh l mt plasmid ln vi 2 phn, chc nng ring bit. Phn th nht RTF gi l nhn t vn chuyn khng (Resistance transfer factor), khong 80 kb cha nhng gen ca s t sao chp v ca s tip hp. Phn kia nh hn l quyt nh khng (R determinant), kch thc rt thay i v cha gen khng thuc (R genes) RTF v quyt nh khng thng thng to nn mt n v. Nhn t R thng ti t hp vi nhau lm pht sinh nhng t hp mi v khng thuc.

Nhn t R khng nhng c th ly truyn rng ri trong nhiu loi vi khun ng rut m cn c th ly truyn cho nhiu vi khun khc nh vi khun t, vi khun dch hch...

Nhn t R ly truyn trong vi khun qua tip xc nn tnh khng thuc lan trn trong mt qun th vi khun nhy cm nh mt bnh truyn nhim .

3.2. Plasmid khng thuc vi khun Gram dng

S khng ca nhiu chng t cu vng vi penicillin, erythromycin v nhiu khng sinh cng do plasmid gy nn. Plasmid vi khun Gram dng khng th vn chuyn bng tip hp m bng ti np qua trung gian ca phage. Hin nay phn ln nhng chng t cu khng penicillin bnh vin u mang plasmid penicillinase.

4.Thu hoch transposon

Transposon cn gi l gen nhy l nhng on ADN, kch thc nh cha mt hay nhiu gen c 2 u tn cng l nhng chui nucleotic ging nhau nhng ngc chiu nhau (inverted repeat). c th nhy t plasmid vo nhim sc th hoc t nhim sc th vo plasmid hoc t plasmid n plasmid. Tt c mi gen trong c gen khng thuc c th nm trn transposon. Nhng transposon ch o s khng kim loi nng, s to thnh c t v kh nng s dng mt s cht chuyn ha (lactose, raffinose, histidin, hp cht lu hunh) c m t. c bit quan trng trong vi sinh hc l nhng transposon khng khng sinh nh Tn3 mang gen khng ampicillin, Tn5 mang gen khng kanamycin, Tn10 mang gen khng tetracyclin, Tn4 mang gen khng ba khng sinh ampicillin, streptomycin v sulfamit.

NH HNG CA CC NHN T NGOI CNH

N S PHT TRIN CA VI SINH VT

Mc tiu hc tp1. Trnh by c tc ng ca mt s nhn t vt l, ho hc v sinh hc ln s pht trin ca vi sinh vt.

2. Gii thch c c ch tc ng ca mt vi yu t vt l, ho hc v sinh hc ln s pht trin ca vi sinh vt.

S tn ti v pht trin ca vi sinh vt chu nh hng trc tip ca cc nhn t ca mi trng xung quanh nh nhit , nh sng, ha cht, cc bc x, pH...Cc nhn t ny c th chia lm 3 nhm ln: cc nhn t vt l, cc nhn t ha hc v cc nhn t sinh hc. Hiu c nh hng ca cc nhn t ny i vi s pht trin ca vi sinh vt ng dng trong cng tc tit trng, kh trng cc dng c y t, dc phm, ty u mi trng, phng m, phng bnh nhn, nghin cu vi sinh vt...

I. NHN T VT L

1. Vn ng c gii

Vi sinh vt chu nh hng ca cc tn s rung ng ca mi trng, yu t ny c th c tc dng kch thch hay c ch s pht trin ca vi sinh vt v tiu dit vi sinh vt.

- Khi lc canh khun vi tn s va (1-60 ln / pht ) th c tc ng tt n s pht trin ca vi khun do tng kh nng thng kh, thc y s phn bo...

- Khi lc mnh th li c ch s pht trin ca vi khun, nu lc ko di th c th tiu dit cc vi sinh vt.

Vn ng c gii thng c ng dng khi nui cy vi sinh vt lm tng sinh khi hoc thu nhn s lng ln sn phm do vi khun bi tit ra...

2. Lm mt ncNc cn thit cho hot ng sng ca vi sinh vt, lm mt nc th vi sinh vt s cht. Tc cht ty thuc vo mi trng vi khun sng.

- Huyn dch vi khun trong nc nu em lm kh th vi khun cht rt nhanh.

- Huyn dch vi khun trong th keo khi lm kh vi khun cht chm hn.

- Huyn dch vi khun nu lm ng bng nhanh trc ri mi tin hnh lm mt nc th vi khun cht rt t. Phng php ny c p dng lm ng kh vi khun nhm bo qun vi khun trong thi gian di.

Trng thi nha bo l trng thi mt nc t nhin ca vi khun. Nha bo chu c kh hanh lu di.

3. Hp phThan hat, gel albumin, mng lc s... c kh nng hp ph vi khun v s hp ph ny lm thay i kh nng sng ca vi khun. c p dng lm v khun cc sn phm ca huyt thanh, cc sn phm khng chu nhit...

4. pH

pH ca mi trng c nh hng n hat ng sng ca vi khun do lm thay i s cn bng v trao i cht gia mi trng v vi khun c th git cht vi khun. Mi loi vi khun ch thch hp vi mt gii hn pH nht nh (t 5,5 n 8,5), a s l pH trung tnh (pH=7), bi v pH ni bo ca t bo sng l trung tnh. mi trng kim, Pseudomonas v Vibrio pht trin tt, c tnh ny rt hu ch phn lp chng. Trong khi Lactobacillus pht trin tt hn pH=6 hoc thp hn. Trong qu trnh iu ch cc mi trng nui cy phi m bo pH thch hp th vi khun mi pht trin tt. Trong tit khun hoc kh khun ngi ta c th s dng cc ha cht c pH rt axit hoc rt kim loi tr vi khun.

5. p sut

5.1. p sut thy tnh (p sut c gii)Vi khun c kh nng chu c p sut cao ca khng kh, thng t 2000-5000 atm i vi virus, phage; t 5000-6000 atm i vi cc vi khun khng c nha bo; t 17000-20000 atm i vi cc vi khun c nha bo. C ch tc ng ca p sut c gii i vi vi khun cha c r.

5.2. p sut thm thup sut thm thu ca mi trng xung quanh c tc ng mnh n t bo vi khun do tnh thm thu ca mng nguyn tng. a s cc vi khun pht trin thch hp khi mi trng c p sut thm thu bng 7 atm (dung dch NaCl 0,9%).

- Trong dung dch nhc trng, do p sut thm thu bn trong t bo cao hn mi trng nn nc b ht vo t bo vi khun lm t bo phnh to ln v v.

- Trong dung dch u trng, p sut thm thu mi trng cao nn nc b ht ra mi trng lm t bo b teo li.

6. Nhit Nhit l yu t nh hng rt ln n s pht trin ca vi khun. Mi loi vi sinh vt pht trin trong mt gii hn nhit nht nh, da vo khong nhit pht trin ti u, vi khun c th c chia lm 3 nhm: nhm a m c nhit ti u gia 20oC-45oC, nhm a lnh c nhit ti u di 20oC v nhm a nng c nhit ti u trn 45oC. nhit qu thp vi khun khng pht trin c nhng c th cn sng; cn nhit cao hoc rt cao th vi khun b tiu dit.

- Nhit thp: nhit thp cc phn ng chuyn ha ca vi khun b gim i, c th b ngng li. Mt s vi sinh vt b cht nhng a s vn sng trong thi gian di. Lc lm ng bng vi sinh vt th mt s b cht, nhng nu lm ng bng rt nhanh th s vi sinh vt sng st nhiu hn. Ngi ta s dng c im ny bo qun cc chng vi khun nhit thp.

- Nhit cao: Nhit cao c kh nng git cht vi khun. Sc khng ca vi khun vi nhit cao ty tng chng loi v ty theo trng thi sinh trng hay trng thi nha bo. a s cc vi khun trng thi sinh trng nhit 56-60oC trong 30 pht l cht v 1000C th cht ngay. Th nha bo chu c nhit cao hn v lu hn 1210C trong 15-30 pht ni hp mi cht hoc 1700C trong 30 pht - 1 gi nhit kh mi b tiu dit.

- C ch tc dng ca nhit cao i vi vi khun:

+ Protein b ng c

+ Enzyme b ph hy

+ Tn thng mng nguyn tng lm thay i tnh thm thu.

+ Ph hy cn bng l - ha trong t bo do tng tc phn ng sinh vt ha hc.

+ Gii phng axit nucleic

7. Bc x

- nh sng mt tri: nh sng mt tri do c tia cc tm c bc sng t 200-300 nm, nht l 253,7nm, c tc dng st khun.

- Tia Rnghen: c hiu ng dit khun v gy t bin i vi vi sinh vt

- Nguyn t phng x: to ra cc bc x (, ( v ( trong tia (, ( c tc dng dit khun hay c ch vi khun pht trin. Cn tia ( t c tc dng.

C ch tc dng ca bc x: Do nguyn tng ca vi khun c thnh phn cu to bng cc phn t rt phc tp, cc phn t ny c kh nng hp th mt cch chn lc nhng tia bc x c bc sng khc nhau. Th d nh axit nucleic ca vi khun c kh nng hp th tia bc x di 253,7nm, lc qu trnh sao chp ca DNA b bin i hoc b c ch hoc DNA b ph hy khng thun nghch lm vi khun cht.

8. Siu mKhi nhng tn s ca chn ng vt qu 20.000 ln/1 pht th gi l siu m (do tai ta khng nghe c na). Siu m c kh nng git cht vi khun do nhng chn ng c tn s cao pht sinh ra p sut co gin cao lm cho t bo vi khun b x tan; cng c th nc trong t bo vi khun di tc dng ca siu m pht sinh ra H2O2 c tc dng git cht vi khun; siu m cng c th ph hy h thng keo lm cho cht keo ng li.

9. Tia laserTia laser do nng lng cao v tp trung nn trong mt thi gian cc k ngn c th lm cho vt cht nng chy v bay hi, c th tng nhit , p sut ti ch ln rt cao nn cng c tc dng git cht vi khun.

II. CC NHN T HA HC

Cc ha cht trong mi trng c nh hng hoc kch thch hoc c ch s pht trin ca vi khun. Cc ha cht c tc dng kch thch s pht trin vi khun c ng dng trong nui cy vi khun... Cc ha cht c tc dng c ch hoc tiu dit vi khun c s dng lm cht ty u, cht kh khun hoc st khun ty theo mc ch s dng v nng s dng.

1. Cht ty u, cht kh khun

- Cht ty u l nhng ha cht c kh nng git cht cc vi khun gy bnh v vi sinh vt khc, cn i vi nha bo th tc dng git khun mt phn. Cht ty u s dng trn b mt cc dng, cc dng c y t, cc cht thi ca bnh vin...

- Cht kh khun l nhng ha cht c tc dng ngn cn s pht trin ca vi khun, cht ny ch c tc dng git cht vi khun mt phn nhng c tc dng c ch vi khun rt mnh. Cht kh khun c th dng v khun vt m, ni tim chch...Thc ra cht ty u v kh khun ch khc nhau v nng khi s dng. V d: phnol nng 2-5% th dng ty u, cn khi nng thp hn 100 -1000 ln th dng lm cht kh khun.

- Ch s phenol l t l gia nng ti thiu ca cht ty u c tc dng dit khun v nng ti thiu ca phenol khi s dng i vi mt chng vi khun nht nh. Ch s ny c dng lm n v nh gi tc dng dit khun ca mt ha cht.

2. Cc nhn t ha hc nh hng n s pht trin ca vi khun

2.1. Axit v bazAxit v baz c kh nng phn li thnh ion H+ v OH- rt mnh, lm cho pH ca mi trng thay i v c tc dng dit khun hoc c ch s pht trin ca vi khun.

2.2. Cc mui kim loiKhi ha tan vo trong nc th mui ca nhiu kim loi nng c kh nng phn li thnh ion v c tac dng dit khun, kh nng dit khun ca cc mui kim loi nng c th do s kt hp ca cc ion kim loi vi nhng nhm -SH ca protein t bo. Hot tnh dit khun theo th t Hg, Ag, Cu, Zn. V d :

- Mui thy ngn: c dng nhiu nht ty u nh sublim (HgCl2),...

- Mui bc: c tc dng st khun nh nitrat bc (dung dch argyrol).

- Mui ng: sunpht ng dng cha bnh nm ngoi da.

- Mui vng: c dng iu tr cc bnh do vi khun khng cn- axit di dng mui thiosunpht.

2.3. Nhm HalogenTc dng dit khun do phn ng oxy ho v halogen ho cc cht hu c. Phn ng oxy ho xy ra nhanh v khng thun nghch, cn halogen ho th chm hn v khng mnh bng. Nhng phn ng ny xy ra vi nhiu cht hu c khc nhau, do s lm gim hot tnh dit khun trong nhng dung dch c nhiu cht bn hu c hay cc cht oxy ho v halogen ho khc, nht l amoniac.

+ It: Cn it (7% I, 3% KI...) thng c s dng st trng da, c ch s phenol cao.

+ Clo: thng c dng dng kh nguyn cht v dng hp cht hu c hay v c. Clo dng kh khun nc sinh hot, nc b bi.

Cl2 + H2O HCl + HClO

2HClO 2HCl + O2

(HClO c hot tnh gii phng oxy, nhng khng dit c cc vi khun lao v virus ng rut).

Chlorua vi thng c s dng nht kh trng cht nn, cht thi v dng c th hoc rc h x. Chloramin tinh khit 1% trong nc c kh nng kh trng bn tay bng cch ngm 5 pht trong dung dch ny v c th kh khun dng c bng cch ngm 20 pht.

2.4. PhenolL mt cht ty u tt c s dng t rt sm. Tuy nhin phenol c vi da, nim mc v gy c thn kinh.

- Nng : khong 1% c th git cht vi khun trng thi sinh trng

- Nng 5% c th git cht vi khun trng thi nha bo.

2.5. CnRu ethylic c tc dng st trng da. Tc dng dit khun ty theo nng , cao nht l dung dch ethanol 70% v nng thp hn th tc dng dit khun gim. Cn tuyt i th tc dng dit khun km. Ngoi dung dch ethanol, dung dch isopropanol 70% cng thng c s dng.

2.6. Andehyt (cc tc nhn ankyl ha)

Rt c i vi t bo vi khun. Formol l cht dit khun mnh nht ca nhm ny, n c s dng ph hu hiu lc ca c t hoc ca virus m khng ph hu kh nng sinh khng, c th s dng ty u cc phng bnh, qun o, chn mn...

2.7. Cc cht oxy ho khc v cc thuc nhum:

H2O2, KMnO4, thuc nhum thng pha thnh dung dch lng dng lm cht st khun. Thuc nhum thng c dng c ch s pht trin ca tp khun trong cc mi trng chn lc.

2.8. Cc tc nhn c hot tnh b mtNhng hp cht ny c gi l thuc ty tng hp. Dit khun mnh m nht l nhng thuc ty cation trong hiu qu hn c l nhng hp cht amonium bc 4 nh benzalkonium chlorua. Nhng hp cht ny c s dng rng ri kh khun. Chng tc ng bng cch lm tan mng t bo vi khun do ha tan mng lipit che ch vi khun v lm bin th protein.

3. C ch tc ng ca cc ha cht i vi t bo vi khun.

- Ph hy mng t bo: do ion ha, thay i sc cng b mt, lm tan mng lipit che ch vi khun...

- Bin i chc nng ca protein v cc axit nucleic...

- Tc ng ha hc lm gii phng oxy phn t, clo... c tc dng git cht vi khun.

4. Cc yu t nh hng n tc dng ca cc cht ty u v st khun.

- Nng ca ha cht: nng cng cao th tc dng cng mnh.

- Thi gian tip xc: tip xc cng lu th tc dng cng mnh.

- Nhit

- Thnh phn ca mi trng xung quanh: do cc cht hu c c tc dng bo v vi khun hoc tc dng vi ha cht lm gim hiu lc.

- Mt vi sinh vt ti ni kh trng

- Kh nng khng ca vi sinh vt (virus c lp v lipit s nhy cm vi cht ho tan lipit nh cn, phenol hn l nhng virus khng c v).

III. NHN T SINH VT

Trong qu trnh tn ti ca vi sinh vt nu chng phi sng trong iu kin c vi sinh vt khc th chng c th b cnh tranh sinh tn, b tiu dit hoc song song tn ti.

1. Cht i khng (Bacterioxin)

Nhiu loi vi khun khi pht trin th tng hp cc cht i khng c tc dng c ch cc vi khun cng loi hoc cc loi ln cn. V d : Colixin ca E.coli, Staphylococxin ca T cu...Chng c bn cht protein hoc phc hp gluxit-lipit-protein, c tc ng c hiu vi cc vi khun nhy cm.

2. PhageL virus ca vi khun, phage xm nhp cc vi khun c hiu, nhn ln v ph v t bo vi khun. Phage cng c th cng tn ti v nhn ln vi vi khun trng thi n ha.

3. InterferonL cht do t bo sn sinh ra khi b virus xm nhp, c bn cht glycoprotein, c tc dng c ch s nhn ln ca virus.

4. Cht kch thchMt s vi khun khi pht trin sn sinh ra mt cht lm thun li cho vi khun khc pht trin. V d nh Hemophilus mc tt xung quanh khun lc T cu (do T cu sinh ra yu t V cn thit cho Hemophilus pht trin) ...

TIT TRNG - KH TRNG V KHNG SINH

Mc tiu hc tp1. Nu c cc phng php tit trng v kh trng trong phng th nghim.

2. Trnh by c nh ngha khng sinh, cc c ch tc dng ca khng sinh.

3. K c cc nhm thuc khng sinh v hiu qu ca chng vi cc nhm vi khun chnh.

4. M t c cc c ch khng ca vi khun vi khng sinh, ngun gc ca s khng, cch theo di s khng v mc ch ca phi hp khng sinh trong iu tr bnh nhim trng

I. TIT TRNG V KH TRNG

1. Tit trngTit trng l s lai b tt c vi sinh vt sng (gm th dinh dng v nha bo ca chng) bng nhit , bng tia bc x, bng cc ha cht hoc bng cc bin php c hc. Tit trng l cng vic cn thit trong y hc nhm git cht cc vi sinh vt sinh bnh khi dng c y t, sinh vt phm, dc phm... Trong phng th nghim vi sinh vt, tit trng l bin php khng th thiu c cho vic phn lp, nui cy v lu gi cc vi khun thun khit. Ngi ta dng nhiu phng php tit trng khc nhau trong phng th nghim vi sinh hc.

- Cc phng php tit trng bng dng nhit nh t nng trn ngn la ,dng l sy kh 160-1700C, dng nhit m trong ni p sut, hoc chng cch thy ngt qung kiu Tyndal .

- Tit trng bng cc tia bc x: cc tia bc x cc tm , tia gamma, tia beta c tc dng git cht vi sinh vt, c dng tit trng dng c, ch phm sinh hc...

- Tit trng bng c hc dng cc my lc, vi khun s b gi li pha trn my lc. Phng php ny dng tit trng cc mi trng nui cy vi khun.

2. Kh trng (hay kh khun)

Thut ng ny dng cho cc tc nhn vt l, v thng l ha hc c kh nng git cht vi sinh vt sng trn cc dng, dng c th nghim, phng th nghim, phng bnh ...

Tc nhn vt l nh tia cc tm c dng kh trng phng m, phng nui cy vi khun .

Nhiu ha cht c bit c dng cho mc ch kh trng phng lm vic, phng th nghim, kh trng cc dng, dng c th nghim nh x phng, phenol , cc hp cht halogen, cc mui kim loi, cn...

Thut ng st khun (antiseptic) c s dng cho cc ha cht dng git cht vi sinh vt trn b mt ca c th con ngi hoc ng vt m khng lm tn thng t chc ca c th. Cc ha cht ny t c vi c th v thng nng thp. Nh vy mt ha cht c th s dng lm dung dch kh khun hoc s dng st khun ph thuc vo mc ch s dng v nng cht s dng v d phenol khi nng 2-5% c dng nh cht kh trng, cn khi nng thp hn 100 n 1000 ln c dng lm cht st khun .

II. CC CHT KHNG SINH

1. nh ngha

Thut ng khng sinh theo nh ngha ban u l nhng tc nhn khng khun c ngun gc t vi sinh vt, chng c tc dng chng vi khun hu hiu nng rt thp. Lc u cc khng sinh u chit t mi trng nui cy nm mc hoc vi khun, sau nhiu khng sinh c bn tng hp bng cch bin i cu trc phn t ca khng sinh thu c khng sinh mi.

Hin nay khng sinh c xem nh l nhng hp cht ha hc c tc dng cn khun hoc dit khun vi c ch tc ng mc phn t, hu hiu liu lng thp v c th s dng iu tr bnh nhim trng.

Cc khng sinh c tc dng c hiu i vi mt loi vi khun hoc mt nhm vi khun nht nh. Cc khng sinh c hot tnh khc nhau, c loi c ph khng khun rng, c loi c ph khng khun hp.

2. C ch tc dng ca khng sinh

2.1. c ch tng hp vch t bo

Khc vi t bo ng vt, vi khun c vch t bo. Loi b vch hoc ngn cn s to thnh vch u lm tan t bo vi khun. Vch t bo vi khun cha mucopeptit cn gi l murein hay peptidoglycan. Cc penicilline v cephalosporin tc ng ln cc phn t protein chn lc c hiu nn c ch s lin kt ngang cui cng ca cu trc mucopeptit ca vch t bo, vi khun d dng b tan.

Cc khng sinh khc nh bacitracin, vancomycin, novobiocin, D-cycloserin cng c ch s to vch ca vi khun bng c ch s hnh thnh mucopeptit ca vch .

2.2. c ch chc nng ca mng nguyn tng

Mng nguyn tng hot ng nh mt mng bn thm. Mng ny thm thu cc cht chn lc v nh vy kim sot c cc thnh phn bn trong ca cc t bo. Nu s ton vn ca mng nguyn tng b ph v th cc thnh phn ni bo thot ra khi t bo v t bo cht. Mng t bo ca mt s vi khun v nm d b ph v bi mt s thuc khng sinh hn t bo ng vt do hot tnh tc dng chn lc ca cc khng sinh ny ln cc nhm cu trc ha hc c bit c mng ca vi khun hoc ca nm m khng c t bo ng vt. Polymycin c tc ng mng nguyn tng ca vi khun gram m, polyen c tc ng mng nguyn tng ca nm.

2.3. c ch tng hp protein

Nhiu thuc khng sinh c ch tng hp protein ca vi khun:

2.3.1.Chloramphenicol: chloramphenicol v cc dn cht thuc nhm ny ngn cn s kt hp axit amin vo chui peptit mi sinh n v 50S ca ribosome vi khun qua vic cn tr tc ng ca enzyme peptidyl-transferaza.

2.3.2. Cc tetracyclin: tetracyclin v cc thuc khng sinh nhm ny c ch s tng hp protein ca vi khun bng cch ngn cn s gn lin ca amino acyl-RNA vn chuyn vo n v 30S ca ribosome .

2.3.3. Cc macrolid v lincomycin: Cc khng sinh nhm ny ngn cn s tng hp protein bng cnh tranh v tr kt hp ca axit amin ribosome v bng cch phong b phn ng dy chuyn aminoacyl.

2.3.4. Cc aminoglycoside: cc thuc khng sinh nhm aminoglycoside c ch tng hp protein bng cch gn vo protein tip nhn trn n v 30S ca ribosome lm c sai thng tin ca ARN thng tin lm hnh thnh cc protein khng c hat tnh, ngoi ra cn lm tch cc ribosome trng thi polymer thnh monomer

2. 4. Tc dng c ch s hnh thnh acid nucleic

2.4.1. Cc sulfonamid v trimethoprim: i vi nhiu vi sinh vt, axit para-aminobenzoic (vit tt l PABA) l mt cht chuyn ha cn thit trong qu trnh tng hp axit folic cn thit tng hp purin v ADN. Sulfonamid do c cu trc tng t nh PABA nn c th i vo phn ng thay cho PABA, hu qu l mt cht tng t nh axit folic nhng khng c hat tnh c to thnh v ngn cn s pht trin ca vi khun.

Trimethoprim c ch enzyme dihydro folic reductase, enzyme ny bin i axit dihydro folic thnh axit tetrahydro folic, mt giai an trong chui phn ng tng hp purin v DNA.

S phi hp mt trong cc sulfonamid vi trimethoprim, hai cht tc ng hai khu khc nhau ca mt qu trnh tng hp lm tng r hat tnh ca thuc, cotrimoxazol (sulfamethoxazol v trimethoprim) l ch phm phi hp s dng hiu qu trong iu tr cc bnh nhim trng

2.4.2. Rifampin: Rifampin v cc dn cht kt hp vi ARN polymerase ph thuc ADN v nh th c ch s tng hp ARN vi khun.

2.4.3.Cc quinolone: Cc quinolon v cacboxy fluoroquinolon kt hp vo ADN gyrase nn c ch tng hp ADN.

3. Cc nhm thuc khng sinh

3.1. Sulfonamid

L nhng hp cht thay th nhm amit (SO2NH2) hoc nhm amin (NH2) ca axit sulfanilamic.

Sulfonamid c tc dng cn khun i vi vi khun gram m v vi khun gram dng. Chng c ch nhiu vi khun gram dng v vi khun ng rut bao gm E.coli, Klebsiella v Proteus.

Cc sulfonamid c s dng rng ri nh sulfaguanidin, sulfadiazim, sulfisoxazol, sulfamethoxazol, sulfadimethoxin....

Tr ngi chnh ca cc thuc nhm sulfamid l vi khun tr nn khng vi thuc nhanh chng, thm vo nhiu sulfamid c th gy phn ng ph nghim trng. Nn hin nay cc thuc nhm sulfamid ch c dng hn ch.

Ch phm sulfamid ang c dng rng ri hin nay l cotrimoxazol l phi hp ca sulfamethoxazol v trimethoprim. Thuc ny c dng trong iu tr cc nhim trng ng tiu ha, h hp v tit niu. Dng phi hp khc l fansidar bao gm sulfadoxin v pyrimethamin c hiu qu trong iu tr st rt, t hiu qu i vi bnh nhim trng .

3. 2. Cc beta- lactamin

Cc thuc ny trong cng thc ha hc c cha vng beta-lactam bao gm cc penicillin v cc cephalosporin.

3.2.1 Cc penicillinCc penicillin c nhn chung l axit 6 amino-penicillanic hp bi mt vng thiazolidin v mt vng (-lactam cc penicillin ny khc vi penicillin khc ch gc R gn vo nhn chung.

Cc penicillin dng trong iu tr thuc 3 nhm chnh :

- Cc penicillin c hot tnh cao i vi vi khun gram dng, b ph hy bi enzyme penicillinase: penicillin G, penicillin V (phenoxy methylpenicillin), benzathin penicillin.

- Cc penicillin c hot tnh i vi vi khun gram dng, khng i vi enzyme penicillinase: methicillin, nafcillin, oxacillin, dicloxacillin .

- Cc penicillin c hot tnh rng i vi c vi khun gram dung v vi khun gram m, b ph hy bi enzyme penicillinase. Cc penicillin nhm ny bao gm:

+ Cc aminopenicillin: ampicillin, amoxicillin, becampicillin, metampicillin.

+ Cc carboxy penicillin: carbenicillin, ticarcillin.

+ Cc ureidopenicillin: azlocillin, mezlocillin, piperacillin.

Ngoi 3 nhm chnh trn hin nay ngi ta cn c cc penicillin phi hp trong ngi ta kt hp cc penicillin khc nhau vi nhng cht c ch enzyme ( lactamase dng iu tr cc nhim trng do vi khun khng sn xut enzyme ( lactamase. Hai cht c ch enzyme ny c dng phi hp vi cc penicillin l axit clavulanic v sulbactam: cc thuc ca s kt hp ny nh: timentin gm ticarcillin v axit lavulanic, augmentin (amoxicillin v a.clavulanic), unasyn (ampicillin & sulbactam).

3.2.2 Cc cephalosporin

Cc cephalosporin c mt nhn chung l axit faminocephalo-sporanic hnh thnh bi mt vng ( lactam kt hp vi mt vng dihydrotiazin thay th hydro cu nhm amin bng cc gc R khc nhau th thu c cc cephalosporin bn tng hp .

Cc cephaloporin c hot tnh vi c vi khun gram dng v vi c vi khun gram m .Da vo tnh khng khun cc cephalosporin c chia cc th h:

- Cc cephalosporin th h th nht:

Bao gm cephalothin, cephazolin, cephalein, cefaclor. Cc thuc ny c hot tnh i vi t cu lin cu A, ph cu, E. coli, Klebsiella, Proteus..

- Cephalosporin th h th hai:

Cc thuc nhm ny c hot tnh tt hn cc thuc cephalosporin th h th nht chng li E. coli, Klebsiella, Proteus, Citrobacter, Enterobacter, H.influenzae, N.gonorrhoe, N. meningitidis. Cc thuc nhm ny gm: cefamandol, cefuroxime, cefonicid, cefoxitin...

- Cephalosporin th h th ba:

C ph tc dng khng khun bao trm ton b vi khun ng tiu ha, tuy nhin c tc dng km vi vi khun gram dng, thuc nhm ny c th chia 02 nhm, nhm c tc dng chng Pseudononas aeruginosa gm ceftazidime v cefoperazone, v cc nhm khng c tc dng chng P. aeruginosa bao gm cefotaxim, ceftazidime, ceftizoxime, moxalactam. Nhiu thuc nhm ny thm vo mng no tt nn c dng iu tr vim mng no do vi khun gram m.

3.2.3. Monobactam v Carbapenem:

Hai nhm thuc ny khc vi cc beta-lactam v cu to ha hc nhng c ch tc dng l c ch tng hp vch tng t nh cch tc dng ca cc beta lactam, aztreonam l thuc thuc nhm monobactam c sn hin nay, ph khng khun gii hn trn vi khun gram m tng t nh cc aminoglycoside.

Imipenem l khng sinh carbapenem c sn hin nay, ph khng khun ca thuc ny c xem l rng nht trong cc thuc khng sinh hin nay bao trm ln cc vi khun gram dng gm c lin cu D, c tc dng chng li hu ht cc vi khun gram m k c P.aeruginosa, v c tc dng chng li vi khun k kh.

3.3. Cc khng sinh aminoglycoside

Gm streptomycin, neomycin, gentamycin, tobramycin, amikacin, kanamycin Cc khng sinh nhm ny c tc dng dit khun bao gm c vi khun gram dng v nhiu vi khun gram m. gentamycin, tobramycin, neomycin c tc dng chng P.aeruginosa, tri li streptomycin c tc dng vi vi khun lao nn l thuc dnh ring iu tr lao.

3. 4. Cc thuc tetracyclinC cng thc ha hc tng t nhau. Cc thuc khc nhau ch cc gc R khc nhau.Cc thuc ny bao gm tetracyclin, chlotetracyclin, oxytetracyclin, doxycyclin, minocyclin, thuc nhm ny c tc dng cn khun vi vi khun gram dng v gram m, cc tetracyclin c hiu qu vi Rickettsia, Chlamydia, Mycoplasma pneumoniae v Leptospira.

3. 5. Chloramphenicol

Lc u chit xut t Streptomyces venezuelae nhng hin nay c tng hp. Thuc ny c tc dng cn khun v ph khng khun rng. N c hiu qu trong bnh thng hn v cc nhim trng do Rickettsia.

3. 6. Macrolit v cc thuc tng t

Cc thuc khng sinh macrolit gm erythromycin, oleandomycin, spiramycin. Cc khng sinh thuc nhm ny c tc dng cn khun, chng tc dng tt trn vi khun gram dng, mt s vi khun gram m nh phy khun t. Erythromycin l thuc an ton nn c dng lm thuc thay th penicillin trong cc nhim trng do vi khun gram dng bnh nhn d ng vi penicillin. Lincomycin v clindamycin c c ch tc dng v hat ph tng t nh erythromycin.

3.7. Polypeptid

Khng sinh nhm polypeptit ch yu l polymycin, ph tc dng ch yu dit khun vi vi khun gram m k c Pseudomonas. Polymycin c vi thn kinh v thn, hin nay t c dng ng ton thn iu tr cc nhim trng gram m. Cac thuc c polymycin thng c dng iu tr nhim trng ti ch.

3.8. Rifamycin

L khng sinh chit sut t Streptomyces mediterranei, cht dn xut bn tng hp l rifampin, hai thuc ny c hat ph i vi mt s vi khun gram m v gram dng, vi khun ng rut, vi khun khng acid cn. Rifamycin do vy l thuc s dng ch yu iu tr bnh lao hin nay.

3.9. Cc quinolon v cacboxy - fluoroquinolon

Hp cht quinolon tng hp u tin l axit nalidixic ch yu dng iu tr nhim trng ng tit niu. Cc cacboxy-fluoroquinolon l cc dn cht t axit nalidixic, cc thuc ny c tc dng dit khun i nhiu vi khun gram dng v vi khun gram m k c t cu khng vi methicillin v P.aeruginosa, chng cn cn c tc dng chng Mycoplasma v Chlamydia. Cc fluoroquinolon c s dng trong nhiu nhim trng cc c quan. Mt s fluoroquinolon thng dng hin nay gm ciprofloxacin, enoxacin, norfloxacin, pefloxacin.4. S khng ca vi khun vi thuc khng sinh

4.1. C ch khng thuc khng sinh ca vi khun

Nhiu c ch khng thuc khng sinh ca vi khun c kho st. nhng chng vi khun khc nhau, s khng vi mt lai khng sinh c th do mt hc nhiu c ch khc nhau.

4.1.1.Tng s ph hy thuc do enzymey l c ch khng thng thng qua trung gian ca plasmid. V d in hnh l enzyme beta lactamase gy nn s khng vi cc khng sinh beta lactamin. Cc vi khun sn xut enzyme penicillinase th khng vi cc penicillin, cc vi khun to c enzyme cephalosporinase th khng vi cc cephalosporin, cc aminoglycoside b bt hat bi cc enzyme phosphorylase, adenylase, acetylase. Chloramphenizol b bt hat bi acetylase.

4.1.2. S bin i receptor ca thucy l c ch quan trng. S bin i protein c hiu vi thuc ribosome lm vi khun tr nn khng i vi thuc khng sinh nh s khng vi cc thuc nhm aminoglycoside, erythromycin, khng vi rifampin trn c s thay i mt amino axit trn tiu n v beta ca enzyme ARN polymerarase ph thuc ADN lm thay i s gn vo enzyme ny ca rifampin. S khng ca sulfonamid v trimethoprim cng tng t do s bin i ca phn t enzyme nn sulfamid khng c nhn vo phn ng tng hp acid folic.

4.1.3.Gim tnh thm mng nguyn tngTnh cht ny do s mt hoc thay i h thng vn chuyn mng nguyn tng. S khng ny gp cc khng sinh nh cc beta lactamin, chloramphenicol, quinolon, tetracyclin v trimethoprim. Ngoi ra ro cn thm thu bnh thng ca mng nguyn tng cng chu trch nhim cho s khng t nhin ca nhiu thuc.

4.1.4.Tng s to thnh mt enzymeC ch ny c th lin quan n s sn xut gia tng s lng enzyme c ch nh c thy mt s vi khun mang plasmid khng thuc hoc lin h n s to thnh mt enzyme mi c i lc mnh hn vi mt c cht khc so vi thuc nh trong trng hp khng vi sulfonamid.

4.2. Ngun gc ca tnh khng thuc

Khng thuc khng sinh vi khun ch yu do s hnh thnh nhng gen khng thuc nhim sc th hoc plasmid tuy nhin mt vi trng thi sinh l c bit vi khun tr thnh khng vi thuc khng sinh. Cc vi khun trng thi ng ngha l khng nhn ln c th khng chu tc ng ca thuc nh vi khun lao. hnh thc mt vch ca mt s t bo vi khun (dng L) s khng b nh hng bi cc thuc c ch to thnh vch nh penicillin sau thi gian dng thuc cc vi khun ny c th ly li cu trc nguyn vn.

4.2.1. Khng thuc do t bin nhim sc thMt qun th vi khun c th cha nhng bin chng t nhy cm hn vi mt th thuc. S hin din ca thuc khng sinh nh th ch chn lc cho php cc chng t nhy cm hn sng st. Nh vy vai tr ca thuc ch nh mt yu t chn lc ch khng c vai tr gy nn s t bin khng thuc. Mt khi c s hin din ca bin chng vi khun khng thuc th bin chng ny c th truyn tnh khng thuc ny n nhng vi khun khc bng nhiu c ch khc nhau: Chuyn th, chuyn np, giao phi.

4.2.2.Khng thuc qua plasmidPlasmid l mt phn t ADN t sao chp nh hin din trong nguyn tng nhiu vi khun. Phn t ADN nh ny thng mang cc gen khng thuc (resistance) nn gi l R plasmid. Cc plasmid ca vi khun thng cn mang trn n cc gen cho php chng gn vo b mt nim mc, to ra c t, v xm nhp, cc plasmid khng thuc ny c th truyn cho nhau gia cc vi khun lm lan nhanh s khng.

4.2.3.Cc c ch lm lan truyn tnh khng thucNh nu trn mt khi xut hin bin chng mang gen khng thuc nhim sc th hoc plasmid, cc bin chng ny c th lan truyn nhanh tnh khng cho vi khun khc bng 3 c ch trao i vt liu di truyn sau :

- Bin np.

- Ti np do bacteriophage.

- Tip hp.Cc phng tin lm ly lan nhanh tnh khng thuc:

- Plasmid: thm vo cc gen khng thuc, trn cc plasmid cn mang cc gen thc y s trao i gen gia cc vi khun.

- Do transposon: y l nhng gen c kh nng di chuyn. Cc transposon c mang nhng gen khng khng sinh c th nhy t plasmid ny n mt plasmid khc hoc t plasmid qua nhim sc th. Mt s transposon khng thuc tm thy vi khun Gram m cn mang gen thc y s ly truyn.

- Do cc integron y l vector c th mang gen khng khng sinh, integron c th chn vo cc v tr nht nh trn nhim sc th

4.2.4.Xc nh nhy cm ca vi khun vi khng sinhHin nay nhiu vi khun khng vi khng sinh gy nn nhiu v dch nhim trng nng, iu ny dn n nhu cu cn c nhng chng trnh theo di tnh khng thuc ca vi khun trn phm vi quc gia v quc t. Kho st v dch t hc tnh khng thuc ca vi khun gip cho cc thy thuc lm sng chn thuc khng sinh thch hp iu tr bnh nhim trng. Xc nh nhy cm ca vi khun vi thuc khng sinh bng nhng phng php phng th nghim tin cy v thng nht c cc d kin c th so snh c. Th nghim nhy cm ca vi khun trong phng th nghim, cn gi l khng sinh , c th c thc hin bng phng php ha long hoc bng phng php khuch tn trn mi trng c. Khi thc hin khng sinh vi khun cn phi c nui cy thun khit, a s vi khun gy bnh ngi khi phn lp cn 16-18 gi mi pht trin, nu bnh phm ch thun mt lai vi khun th cn thm 16-18 gi na lm khng sinh , nh vy kt qu khng sinh sm nht cng mt 36 - 48 gi, trong trng hp bnh phm nhiu vi khun, hoc nhiu vi khun pht trin chm cn thi gian lu hn. i vi mt s vi khun m tnh khng sinh n nh v r rng th khng cn thit phi lm khng sinh nh vi khun bch hu, lin cu A tan mu (. Tnh cht khng khng sinh ca vi khun c tnh cht dch t, do vy kt qu khng sinh ca cc vi khun gy bnh c th khc nhau gia bnh vin ny v bnh vin khc v nhng vng khc nhau, ngay c trong cng mt bnh vin nhy cm ca vi khun cng thay i hng ngy. V vy cc phng th nghim vi khun bnh vin cn lm khng sinh chn khng sinh thch hp trong iu tr bnh nhim trng .

4.2.5. Phi hp khng sinhPhi hp khng sinh iu tr bnh nhim trng nhm mt s mc tiu sau :

- Gim kh nng xut hin chng vi khun khng. i vi vi khun khng do t bin th phi phi hp khng sinh lm gim tn sut t bin kp, v d t bin ca vi khun lao khng streptomycin l 10-7, t bin khng rifamycin l 10-9 th xc xut t bin khng c vi c hai th thuc trn l 10-7x10-9 = 10-16. y chnh l l do phi phi hp khng sinh iu tr lao.

- iu tr cc nhim khun hn hp : Mt lai khng sinh c ph tc ng trn mt nhm vi khun nht nh. Trong cc nhim khun do nhiu lai vi khun th phm nh vim phi, vim phc mc... thng do c vi khun i kh v vi khun k kh. Phi hp khng sinh th s dit dc c hai lai vi khun ny.

- tng kh nng dit khun: V d phi hp sulfamethoxazol v trimethoprim lm tng kh nng dit khun i vi nhiu vi khun so vi khi dng n c mt trong hai thuc trn. Mc ch ny c dng trong trng hp iu tr cc nhim trng do Pseudomonas aeruginosa thng ngi ta phi hp carbenicllin v gentamicin...

I CNG VIRUS

Mc tiu hc tp

1. Trnh by c nhng c im , kch thc, hnh th v cu trc ca virus.

2. Trnh by c s nhn ln ca virus v hu qu ca s nhn ln ca virus trong t bo.

3. Trnh by c cc hnh thi nhim virus v cc phng php nui cy virus.

I. S LC LCH S PHT HIN VIRUS

Nm 1796 E.Jenner cho chng u phng bnh u ma. L.Pasteur d tm ra vaccine chng bnh di vo nm 1885, nhng cha chng minh c tc nhn gy bnh v chng khng trng thy c knh hin vi quang hc v khng mc mi trng nui cy nhn to.

Nm 1892 D.I. Ivanovski chng minh c rng mm bnh gy bnh khm thuc l c th chui qua cc lc vi khun bng s. Ivanovski cho rng l mt cht c tng t nh c t do cy b bnh tit ra.

Nm 1898 M.W.Beijerinck chng minh rng chnh tc nhn gy bnh khm thuc l ch khng phi cht c ca n i qua c lc vi khun v ng dng ting Latin l virus (mm c) gi mm bnh ny.

Nm 1898 F.Loeffler v P.Frosch chng minh c tnh qua lc s ca tc nhn gy bnh l mm long mng b .

Nm 1915 - 1917 F.W.Twort v F.H. dHrelle pht hin ra virus ca vi khun v t tn l Bacteriophage, sau ny thng gi tt l phage.

Nm 1935, W.M. Stanley ln u tin tch bit v kt tinh c virus khm thuc l.

T nm 1940 tr i knh hin vi in t c hon thin dn cho php quan st c hnh dng v cc thnh phn cu trc ca virus.

II. NHNG C IM CA VIRUS

Virus l tc nhn nhim trng nh nht (ng knh t 20 - 300 nm ) c th lt qua cc lc vi khun, c cu to rt n gin. Virus l mt i phn t nucleoprotein c c tnh c bn ca mt sinh vt, nhng khng c kh nng t sinh sn, khng c cu to t bo, khng c qu trnh trao i cht v c th coi chng l trung gian gia cc cht sng v cht v sinh.

Virus khc bit vi cc vi sinh vt khc cc c im sau y:

- Virus ch cha mt loi axit nucleic duy nht: hoc l ADN hoc l ARN, khng bao gi cha ng thi c 2 loi axit nhn.

- Virus sinh sn bng cch sao chp t vt liu di truyn duy nht ca chng, khng phn chia bng cch phn i nh cc vi khun.

- Virus k sinh bt buc trong t bo sng, chng da vo ngun nng lng v b my ca t bo (v d cc ribosome, ARN vn chuyn...) tng hp protein.

- Virus tng hp cc thnh phn ca chng mt cch ring r v sau t lp rp vi nhau to thnh nhng ht virus mi.

- Virus khng nhy cm vi cc khng sinh thng thng.

III. KCH THC, HNH TH V CU TRC CA VIRUS

1. Kch thc

Virus c kch thc rt nh b, c th qua c cc lc vi khun. Chnh v th m ch c th quan st thy virus qua knh hin vi in t.

n v o kch thc ca virus l nanomet (nm)

1 nm =1/1000 micromet

Mi loi virus c mt kch thc nht nh (t 20-300 nm) v khng thay i trong sut qu trnh pht trin.

2. Hnh th

Phn ln cc virus c mt hnh th nht nh, c trng cho tng loi virus.

Mt s loi hnh th virus thng gp:

-Hnh cu : virus cm, si, bi lit.

-Hnh khi a din : Adenovirus, Papovavirus.

-Hnh que : virus khm thuc l.

-Hnh vin gch : virus u ma

-Hnh di trng (inh ghim): phage T2 ca E.coli3. Cu trc

Virus c cu trc rt n gin, khng c cu to t bo. Tt c cc ht virus u c hai thnh phn c bn: axit nucleic l thnh phn mang mt m di truyn ca virus v capsid l v protein bao quanh axit nucleic. Li axit nucleic v capsid hp li to thnh nucleocapsid. i vi mt s virus, nucleocapsid cn c bao quanh bi mt v lipit hay lipoprotein gi l bao ngoi (envelope hoc peplos)

3.1. Axit nucleic ca virus

Mi mt ht virus u c mt trong hai loi axit nucleic hoc l ADN hoc l ARN. Axit nucleic nm gia ht virus to thnh li hay h gen ca virus.

Phn t ADN ca virus phn ln dng ADN 2 si v c mt s t dng ADN 1 si nh Parvoviridae. Phn t ARN ca virus a s dng ARN 1 si, tr mt s t dng ARN 2 si nh Reoviridae.

Cc axit nucleic ch chim 1-2% trng lng phn t ca ht virus nhng c chc nng c bit quan trng :

- Axit nucleic mang ton b m thng tin di truyn c trng cho tng virus.

- Axit nucleic quyt nh kh nng gy nhim trng ca virus trong t bo cm th.

- Axit nucleic quyt nh chu k nhn ln ca virus trong t bo cm th

- Axit nucleic mang tnh khng nguyn c hiu ca virus.

3.2. Capsid

Capsid l cu trc bao quanh li axit nucleic. Bn cht ha hc ca capsid l protein. Capsid c cu to bi cc n v hnh thi gi l capsomer bao gm cc phn t protein c sp xp c trng cho tng loi virus. Cc capsomer c sp xp theo mt trt t khng gian xc nh to nn cc kiu i xng ca capsid : hoc i xng xon hoc i xng khi hoc i xng phc hp.

Capsid ca virus c cc chc nng sau y:

- V protein c tc dng bo v axit nucleic ca virus.

- Protein capsid mang tnh khng nguyn c hiu ca virus.

- Capsid ng vai tr quan trng trong giai on bm v xm nhp t bo ca virus.

- Capsid gi cho hnh th v kch thc ca virus lun lun c n nh.

3.3. V ngoi (envelope)

Cc virus nh Herpesviridae, Flaviviridae, Orthomyxoviridae, Paramyxoviridae,... cn c thm mt lp v bao bc ngoi capsid gi l envelope hoc peplos. Bn cht ha hc ca v ngoi l mt phc hp lipid, protein v gluxit. V ngoi c ngun gc t mng bo tng hoc mng nhn ca t bo ch nhng b virus ci to v mang tnh khng nguyn c hiu cho virus. V ngoi c th b cc dung mi ha tan lipid (nh ether, mui mt , ...) ph hy.

V ngoi ca virus c chc nng :

- Tham gia vo s bm ca virus vo t bo cm th

- Tham gia vo giai on lp rp v gii phng virus ra khi t bo sau chu k nhn ln.

Nhng virus khng c v ngoi gi l virus trn.

3.4. Gai protein

Trn v ngoi ca mt s virus c nhng mu gai protein li ln c th c nhng chc nng ring bit nh ngng kt hng cu t hoc enzyme neuraminidase hot ng .

3.5. Mt s enzyme

Virus khng c mt h enzyme chuyn ha hon chnh nh vi khun, nhng trong thnh phn cu trc ca mt s virus c mt vi loi protein c hot tnh enzyme. Ph bin nht l cc polymerase nh ARN polymerase, ADN polymerase, ADN polymerase ph thuc ARN (enzyme sao chp ngc)...

4. Virion

Ht virus hon chnh c kh nng gy nhim trng cho t bo cm th c gi l virion. Ty theo tng loi virus, virion c th c capsid trn hoc capsid c v ngoi.

5. Pseudovirion

Ht virus nhn vt liu di truyn ca t bo ch trong qu trnh sao chp thay cho axit nucleic ca virus c gi l pseudovirion. Nhng ht pseudovirion ny khi quan st di knh hin vi in t chng ging ht cc virion bnh thng, nhng chng khng c hot tnh nhim trng v khng th nhn ln c. Cc ht ny c kh nng chuyn cc gen ca t bo t mt t bo ch ny n mt t bo ch khc.

6. Viroid

Viroid l mt tc nhn nhim trng nh b gy bnh thc vt v c th mt vi nhim trng virus chm ca ng vt. Tc nhn ny ch c axit nucleic (phn t ARN dng vng kn, trng lng phn t 70.000-120.000) khng c lp protein cu trc.

IV. PHN LOI VIRUS

C nhiu cch phn loi virus. Hin nay vic phn loi virus da theo nhng tiu chun c bn sau y:

- Loi axit nucleic (ADN hoc ARN) v cu trc ca chng (s si).

- i xng ca capsid.

- C hoc khng c v ngoi (envelope).

- Cu trc gen virus

- ng knh v s lng capsomer ca virus

- Cc enzyme

- Nhy cm vi ether

- Tnh khng nguyn

- Triu chng hc

Cn c vo cc tiu chun trn chia virus ra thnh cc h (...viridae), ging (...virus), loi v type virus.

Theo s phn loi hin nay, cc virus ca ngi v ng vt c xng sng c chia thnh 22 h khc nhau: 8 h virus cha ADN v 14 h virus cha ARN.

Cc h virus cha ADN gm c:

- Parvoviridae

- Iridoviridae

- Polyomaviridae

- Poxviridae- Papillomaviridae

- Hepadnaviridae

- Adenoviridae

- Herpesviridae

Cc h virus cha ARN gm c:

- Reoviridae

- Paramyxoviridae

- Picornaviridae

- Rhabdoviridae

- Astroviridae

- Filoviridae

- Caliciviridae

- Arenaviridae

- Togaviridae

- Coronaviridae

- Flaviviridae

- Bunyaviridae

- Orthomyxoviridae

- Retroviridae

V. S NHN LN CA VIRUS

Virus khng c qu trnh trao i cht, khng c kh nng t nhn ln ngoi t bo sng. V vy s nhn ln ca virus ch c th c thc hin trong t bo sng nh vo s trao i cht ca t bo ch. iu ny cho thy tnh k sinh ca virus trong t bo sng l bt buc.

S nhn ln ca virus l mt qu trnh phc tp, trong axit nucleic ca virus gi vai tr ch o truyn t cc thng tin di truyn ca chng cho t bo ch. Virus hng cc qu trnh trao i cht ca t bo ch sang vic tng hp cc ht virus mi.

Ni chung qu trnh nhn ln ca virus trong t bo c chia thnh 5 giai on :

Hp ph Xm nhp Tng hp cc thnh phn cu trc Lp rp Gii phng.

1. S hp ph ca virus vo b mt t bo

S hp ph xy ra khi cc cu trc c hiu trn b mt ht virus gn c vo cc th th (receptor ) c hiu vi virus nm trn b mt ca t bo. Do tnh c hiu trn m mi loi virus ch c th hp ph v gy nhim cho mt loi t bo nht nh gi l cc t bo cm th vi chng. V d virus cm ch gy nhim t bo biu m ca ng h hp trn, virus HIV ch xm nhp t bo bch huyt gi l t bo lympho CD4.

2. S xm nhp ca virus vo trong t bo

Cc virus ng vt sau khi gn vo cc th th c hiu trn b mt t bo cm th s xm nhp vo t bo theo c ch m bo. Khi lt vo t bo, capsid ca virus s c enzyme ci v (decapsidase) ca t bo phn hy, gii phng ra axit nucleic ca virus. l giai on ci o.

i vi phage, sau khi hp ph ln b mt t bo th bao ui co rt, li bn trong chc thng mng t bo v bm axit nucleic vo t bo cn casid nm li bn ngoi.3. S tng hp cc thnh phn cu trc ca virus

Ngay sau khi axit nucleic ca virus c gii phng, virus b mt kh nng ly nhim v i vo giai on tim n, trong giai on ny khng thy virus trong t bo na. y chnh l giai on cc virus truyn t nhng thng tin di truyn ca mnh cho t bo ch v bt t bo ch chuyn hng hot ng ca mnh sang vic tng hp cc thnh phn ca virus. Trc ht, cc axit nucleic ca virus c nhn ln, sau protein ca virus c tng hp. Cc axit nucleic ca virus xc nh tnh c hiu ca protein. Nh vy cu trc khng nguyn ca virus khng b ph thuc vo t bo ch m do cc axit nucleic ca virus quyt nh. C ch nhn ln ca cc ADN v ARN ca virus c khc nhau. Di y l v d v ba loi virus c ba loi axt nucleic khc nhau:

- cc virus cha ADN hai si: u tin cc thng tin di truyn ca virus c sao chp t ADN sang ARN thng tin nh ARN polymerase ph thuc ADN. Cc ARN thng tin ca virus s ng vai tr truyn tin to ra cc ADN v cc protein ca virus.

- cc virus cha ARN mt si dng: cc thng tin di truyn ca virus c m ha trong phn t ARN s sao chp sang mt ARN b sung nh c ARN polymerase ph thuc ARN v t chng c lm khun mu to ra cc ARN ca virus. ng thi cc ARN ca virus cng ng vai tr ca ARN thng tin tng hp nn cc protein ca virus.

- cc virus cha ARN c enzyme sao chp ngc: cc thng tin di truyn c m ha trong ARN ca virus c sao chp ngc to ra mt ADN trung gian nh c enzyme sao chp ngc (reverse transcriptase; ADN polymerase ph thuc ARN).T ADN trung gian cc m thng tin di truyn ca virus s c sao chp sang ARN thng tin, t chng tip tc c sao chp tng hp ra cc ARN virus v cc protein virus.

4. S lp rp cc thnh phn ca virus

Sau khi cc thnh phn c bn ca virus c tng hp v c tch ly phong ph trong t bo ch th s bt u qu trnh lp rp. Hnh nh c ch lp rp cc thnh phn ca virion xy ra t pht do kt qu ca s tng tc phn t c bit ca cc cao phn t capsid vi axit nucleic virus to thnh cc virion.

Vic lp rp ng s to ra cc virus hon chnh (cc virion) v nu lp rp sai s to ra cc virus khng hon chnh (ht DIP) hoc to ra cc virus gi (Pseudovirion).

5. S gii phng cc ht virus ra khi t bo

Virus thot ra khi t bo ch theo nhiu kiu khc nhau ty theo loi virus.

Nhiu virus c gii phng theo kiu ph v mng t bo lm hy hoi t bo v cc virus ng lot c phng thch. Hoc c gii phng nh s xut bo (exocytosis) hoc qua cc rnh c bit m khng lm hy hoi t bo ch.

Cc virus c v ngoi c gii phng theo kiu ny chi qua cc ch c bit ca mng t bo ch v virus s nhn c mt phn ca mng t bo ch.

Thi gian nhn ln ca virus thng ngn hn rt nhiu so vi vi khun.V d t virus ban u, mt t bo b nhim virus cm c th to ra hng nghn virus mi sau khong 5 - 6 gi.

VI. HU QU CA S NHN LN CA VIRUS TRONG T BO

Khi virus xm nhp v nhn ln trong cc t bo to ra cc th h virus mi th c th gy nhiu hu qu khc nhau ty thuc vo bn cht sinh hc ca t bo v ca virus.

1.T bo b hy hoi

Sau khi virus xm nhp v nhn ln trong t bo th hu ht cc t bo b ph hy . Do cc hot ng bnh thng ca t bo b c ch , cc cht cn thit cho t bo khng c tng hp m ch tng hp ra cc ht virus mi v vy t bo b cht. y l trng hp hay gp nht .

nui cy t bo in vitro c th thy cc t bo b nhim virus bin dng, dnh li vi nhau, ly gii .

2. T bo b tn thng nhim sc th

Virus c th lm cho nhim sc th ca t bo ch b gy, b phn mnh, b o ln v trt t sp xp v gy ra cc hu qu nh:

2.1. D tt bm sinh, thai cht lu

ph n c thai, c bit trong ba thng u ca thi k mang thai, m b nhim virus th s lm sai lch nhim sc th c th dn ti mt s thiu ht bm sinh trong qu trnh hnh thnh bo thai v gy ra trng thi nhim virus cho bo thai .

2.2. T bo tng sinh v hn to khi u

Cc t bo b nhim mt s loi virus (ch yu l cc virus gy ra khi u) c hin tng mt c ch tip xc khi t bo sinh sn nn to ra nhng m t bo chng cht ln nhau .

3. To ra cc tiu th c trng cho cc virus khc nhau

Trong cc t bo nhim virus c th xut hin cc th vi trongnhn (Adenovirus ), hoc trong bo tng (tiu th Negri ca virus di ), hoc c hai ni (virus si ). Bn cht cc tiu th c th do tch t nhng virion hoc nhng thnh phn ca virion hoc c th l cc ht phn ng ca t bo khi nhim virus .

Cc tiu th ny c th nhum soi thy di knh hin vi quang hc v da vo c th chn on gin tip s nhim virus trong t bo .

4. To ht virus khng hon chnh (DIP: Defective interfering particles)

Ht virus khng hon chnh l virus ch c capsid, khng c hoc c khng hon chnh axit nucleic. Do vy cc ht DIP khng c kh nng nhn ln c lp khi vo trong cc t bo, c ngha l ht DIP khng c kh nng gy nhim trng cho t bo. Nhng ht DIP c th giao thoa c hiu vi nhng virus ng chng .

5. Cc hu qu ca s tch hp genom virus vo ADN t bo ch

Axt nucleic ca virus tch hp vo ADN ca t bo ch c th dn ti cc hu qu khc nhau:

- Chuyn th t bo (transformation) v gy nn cc khi u hoc ung th.

- Lm thay i khng nguyn b mt ca t bo.

- Lm thay i mt s tnh cht ca t bo.

- T bo tr thnh t bo sinh tan.

6 . Kch thch t bo tng hp Interferon

Interferon l nhng glycoprotein c trng lng phn t khong 17.000 - 25.000 Daltons do cc t bo tng hp ra sau khi b kch thch bi cc cht cm ng sinh interferon nh cc virus hoc cc cht cm ng khc.

C 3 loi Interferon: Interferon-alpha, interferon-beta v interferon-gama. Cc loi ny c phn bit bi cc khng th c hiu. Interferon-alpha thng do cc t bo bch cu sinh ra. Interferon-beta c sn xut bi cc nguyn bo si. Interferon-gama l mt lymphokin do cc t bo lympho T sinh ra.

Mt s tnh cht ca interferon:

- Tnh khng nguyn yu.

- Xut hin sm (vi gi ) sau kch thch ca cht cm ng.

-Tnh cht chng virus ca interferon mang tnh c hiu loi nhngkhng c hiu vi virus: Interferon do cc t bo loi no sinh ra th ch c tc dng c ch s nhn ln ca virus t bo ca loi (v d ch c interferon sn xut t cc t bo c ngun gc t ngi mi c tc dng bo v cho ngi). Tri li, interferon c ph tc dng rng c ch s nhn ln ca nhiu loi virus khc nhau ch khng phi ch vi virus cm ng sinh interferon.

- Interferon khng tc ng trc tip ln virus nh khng th m phn ng c ch s nhn ln ca virus xy ra bn trong t bo.

C ch sinh interferon ca t bo:

t bo ngi c 15 gen khc nhau m ha cho interferon-alpha, ch c 1 gen m ha cho interferon-beta v 1 gen m ha cho interferon-gama. Bnh thng cc gen ny trng thi c ch v khng hot ng. Cc cht cm ng sinh interferon c tc dng gii c ch cho cc gen ny lm cho chng tr li dng hot ng v do t bo s tng hp ra cc Interferon. Cht cm ng quan trng nht i vi cc gen alpha v beta l cc virus, nhng i vi gen gama l cc cht hot ha lympho bo T. Hai loi interferon-alpha v interferon-beta c tc dng chng virus mnh hn so vi interferon-gama. Cc interferon-gama c tc dng iu ha min dch v c ch cc t bo ung th mnh hn cc interferon-alpha v interferon-beta.

C ch tc dng chng virus ca interferon:

Interferon gn vo cc th th c hiu dnh cho interferon trn b mt mng t bo, gy ra gii c ch mt s gen m ha cc protein c ch virus. Di tc dng kch thch ca interferon c t nht 2 gen ca t bo c hot ha tng hp ra 2 enzyme l: elF2 kinase v 2, 5-oligoadenylate synthetase. elF2 l yu t khi ng cn thit cho vic gn ARN thng tin vo ribosome; elF2 kinase phosphoryl ha yu t elF2 v lm bt hot elF2 do ngn cn s tng hp protein ca virus. Oligoadenylate c tc dng hot ha ribonuclease ca t bo phn hy ARN thng tin ca virus, do c ch s tng hp protein virus.

Nh vy, interferon ch th hin tc dng chng virus trong t bo sng v thc cht l kch thch t bo dng c ch enzyme phn hy ARN thng tin ca virus v c ch tng hp protein ca virus.

VII. KH NNG GY BNH

Virus c kh nng gy bnh cho ngi. Mt virus c th gy ra nhiu hi chng khc nhau v ngc li mt hi chng c th do nhiu virus khc nhau gy ra.

Nhim virus c th chia lm hai loi chnh ty theo thi gian c tr ca virus trong c th:

1. Tc ng ca virus ln c th xy ra trong thi gian ngn

Loi ny bao gm hai hnh thi nhim virus sau y:

- Nhim virus cp tnh: c c im l thi gian bnh ngn( t mt vi ngy n mt vi tun l ) v tip theo sau cc triu chng c trng cho tc nhn gy bnh pht trin. Nhim virus cp c th kt thc khi hon ton, hoc mt phn, hoc t vong.Trong qu trinh hi phc virus b thi tr.

- Nhim virus khng biu l: nhim virus khng c triu chng, virus trong c th mt thi gian ngn v thi tr nhanh. Xc minh c virus trong c th nh pht hin hiu gi khng th trong huyt thanh.

2. Tc ng ko di ca virus trong c th

C bn hnh thi nhim trng ca loi ny u c c im l trng thi mang virus ko di:

- Nhim virus tn ti dai dng: virus tn ti dai dng khng c triu chng nhng c km theo thi virus ra mi trng chung quanh. Hnh thi ny c th c hnh thnh sau khi bnh phc sc khe. N ng vai tr quan trng trong dch t v l nguy c trc tip gy nhim mi trng. V d bnh vim gan B.

- Nhim virus tim tng: virus tn ti dai dng, khng c triu chng nhng khng thi virus ra mi trng xung quanh. Trong nhim virus tim tng virus c th di dng tin virus, axit nucleic ca virus c th tch hp vo b gen ca t bo ch. Trong mt vi trng hp do nh hng ca mt hay nhiu tc nhn nh chn thng, stress, gim min dch, v.v..., tin virus c th c hot ha v chuyn sang trng thi nhn ln, gy bnh cp tnh cho c th. V d bnh herpes.

- Nhim virus mn tnh: virus tn ti dai dng c km theo mt hoc vi triu chng lc ban u, sau tn thng bnh l tip tc pht trin trong mt khang thi gian di. c im trong tin trin ca nhim virus mn tnh l c nhng thi k sc khe bnh nhn kh ln, bnh thuyn gim, xen k vi nhnhg giai on bnh bng pht, ko di mt vi thng c khi hng nm.

- Nhim virus chm: y l mt hnh thi tc ng c bit gia virus vi c th v c nhng c im l thi gian nung bnh khng c triu chng ko di nhiu thng hoc nm, tip theo l s pht trin chm nhng khng ngng tng ln ca cc triu chng v kt thc bng nhng tn thng rt nng hoc t vong.

VIII. NUI CY VIRUS

Virus ng vt c th nui cy c trn mt h thng t bo sng bao gm ng vt cm th, phi g v cc t bo nui trong ng nghim (in vitro)

1. ng vt th nghim cm th

Trc khi k thut phi g v nui cy t bo c pht minh th tim nhim ng vt l phng php duy nht nui cy virus. Mi loi virus c mt vi ng vt cm th ring. V d i vi Arbovirus, ng vt th nghim cm th thng c s dng l chut nht trng mi .

Ty theo loi virus c th s dng nhng ng vt cm th khc nhau nh chut nht cn b, chut nht, chut lang, th, kh... v nhng ng gy nhim khc nhau: tim, un