Enterobacteriaceae

Tribe Genus

Escherichiaeae EscherichiaShigella

Edwardsielleae Edwardsiella

Salmonelleae Salmonella

Citrobacteriaceae Citrobacter

Klebsielleae KlebsiellaEnterobacterHafniaSerratia

Proteeae ProteusMorganellaProvidencia

Yersinieae Yersinia

Erwinieae Erwinia

Escherichia

• E. coli – Theodore Escherich in 1885– most significant species– common isolate from the colon flora– black/green metallic sheen on EMB– posesses O (Shigella), H and K (Group B N.

meningitidis) Ag.– other species: blattae, vulneris, fergusonii, hermanii

Diarrheal Infections

* EPEC – enteropathogenic E. coli - infantile diarrhea - watery stool w/ mucus but w/o blood

* ETEC – enterotoxigenic E. coli - traveller’s diarrhea - infective dose of 106

- produce LT and ST toxin (hypersecretion)

- non-bloody, watery diarrhea with abdominal cramps and low grade fever

Diarrheal Infections

• EIEC – entero invasive E. coli– cause dysentery ( direct penetration, invasion

and destruction of the intestinal mucosa) – similar with dysentery

– scanty stool with pus, mucus and blood– Sereny test – determines the invasiveness of

EIEC • (+) result – keratoconjunctivitis in guinea pig

Diarrheal Infections

• EAEC – enteroadherent E. coli• cause diarrhea by adhering to the mucosal surface of

intestine.• watery diarrhea, vomiting and dehydration

• EHEC – enterohemorrhagic E. coli or VTEC (E. coli 0157:H7)

• Hemorrhagic diarrhea, colitis and hemolytic uremic syndrome (HUS)

• Bloody diarrhea and crampy abdominal pain

E. coli

• Microscopic Exam

• Growth on Eosin Methylene Blue (EMB)

Other Infections

• Septicemia and Meningitis– accounts for 40% of neonatal meningitis

• Urinary Tract Infections– 90% of cases of UTI

Shigella

4 subgroups Fermentation of lactose mannitol

ODC ONPG

A S. dysenteriae neg neg neg neg

B S. flexneri neg pos neg neg

C S. boydii neg pos neg neg

D S. sonnei neg pos pos pos

Clinical Infections - Shigella

• Shigellosis or Bacillary Dysentery– watery diarrhea– bloody stool with WBC’s & mucus– fecal-oral route (human – only known

reservoir)– self-limiting but highly communicable bec. of

low infective dose (200 bacilli)– Gay bowel syndrome (S. flexneri)

Shigella on CM

Edwardsiella

• Edwardsiella–tarda (human pathogen – bacteremia

and wound infection)–hoshinae (snakes, birds and water)–ictaluri (enteric septicemia in fish)

Salmonella

• Salmonella– 2200 species – 3 common species (cholerasuis, typhi,

enteritidis)– 7 subgroups (with Arizona as groups 3A & 3B)– Virulence factors

• O, H and Vi antigens

• Gram negative rods

• Do not ferment lactose

• Produce H2S

• Major cause of food poisoning in the U.S.

• Cause intestinal infections (enterocolitis); enteric fevers

(typhoid fever); and systemic infections (septicemia)

• Chickens are a major reservoir for this bacteria

• Identification on basis of antigens (O, H, Vi)

Salmonella

Enterocolitis: invasion of epithelial cells of intestines

infectious dose (ID50) ~ 100,000 organisms

infection of gut - inflammation and diarrhea,

self correcting

Typhoid: starts in small intestine: enters and multiplies in

mononuclear cells; spreads to liver, gallbladder,

spleen. Leads to bacteremia with onset of fever.

carrier state - organisms excreted in feces

Septicemia: minority of infections, usually in patients with

underlying disorder

Salmonella - pathogenesis

S. enteritidis

S. typhi

S. typhimurium

Salmonella

Citrobacter• resembles Salmonella but are ONPG (+) &

LDC (-) • Citrobacter species

– freundii (UTI, pneumonia, intraabdominal abscess)

– diversus (neonatal meningitis)– amalonaticus (extraintestinal infections)

C. freundii S. diversus

H2S + -

Indole - +

KCN + -

Klebsiella

Klebsiella-Enterobacter-Serratia-HafniaK. pneumoniae

>Friedlander’s bacilli (encapsulated and mucoid)

> (+) String testK. oxytoca – similar w/ K. pneumoniae except for its indole productionK. ozanae – from nasal secretionsK. rhinoschleromatis – rhinoscleromatis (infection of nasal cavity with intense swelling and malformation of the entire face and neck)

Klebsiella

Enterobacter

–species: habitat: soil, water, dairy products

–normal flora of the git of animals & humans

–motile, ODC & ONPG (+)

Enterobacter

LDC ADH ODC Urease Yellowpigment

• E. cloacae - + + V -• E. aerogenes + - + - -

• E. gergoviae + - + + -• E. sakazakii - + + - +• E. taylorae - + + - -

Enterobacter

Serratia

–opportunistic pathogens–DNAse, lipase, gelatinase

• S. marcescens• S. liquefaciens• S. rubidaea• S. oderifera

Serratia

Hafnia

• Hafnia alvei –2 biotypes

• H. alvei• H. alvei Biotype 1 – associated in

breweries–delayed (+) citrate reaction is its

major characteristic

Proteus• rapid urease producers• Swarming, burned chocolate odor

P. mirabilisP. vulgarisIndole - +ODC + -Fermentation– Maltose - +– Xylose + +– Salicin - +Chloramphenicol S R

Proteus

• Proteus mirabilis• Swarming pehomenon

Morganella

• Formerl known as Proteus• M. morganii – only specie• UTI’s and wound infections

Providencia

• Providencia ( 4 species – P. alcalifaciens, P. rustigianii)

P. rettgeri P. stuartii• Urease + -• Citrate + +

Yersinia

• 11 species– Y. pestis (plague) – bipolar staining (wayson)

• Bubonic – bite of infected flea• Pneumonic• Prefered growth at 25 deg C

– Y. enterocolitica (acute enteritis – appendictis like)• Pig, cats and dogs • Cold enrichment• Motile at RT

– Y. pseudotuberculosis• Pathogen in animals (turkey, geese, doves, farm and domestic

animals)

• Agent of bubonic plague, pneumonic and septicemic plagues• Bubonic plague contracted via flea bites• Y. pestis sheds capsule while growing in invertebrate host.• In humans most of the microbe is taken up and killed by

PMN cells• Some organisms taken up by Macrophages which can’t kill

pestis.• Organism multiples in Mac and resynthesizes capsule• Organism kills Mac and is released into extracellular

environment.• The encapsulated microbe resists phagocytosis and spreads to

lymph nodes which become swollen, and hemorrhagic giving the black buboes characteristic of the disease.

• Microbe rapidly spreads through blood, liver, spleen, lung giving rise to highly contagious pneumonia (highly fatal).

Yersinia

Safety pin appearance

Yersinia pestis

Erwinia

• Plant pathogens• Fail to grow in CM used in the isolation of

enteric bacilli

End of Presentation