Part 1

sheet (13)

made by: aseel twajier

corrected by: Sarah awaisheh

date: 6-11-2016 *slides are within a bold style

Gram Positive Coccus

Staphylococci

-Min(12:40): The Staphylococci are gram-positive spherical cells, non-motile, usually arranged in grapelike irregular clusters. Some are members of the normal microbiota of the skin and mucous membranes of humans; others cause suppuration, abscess formation, a variety of pyogenic infections, and even fatal septicemia. The genus Staphylococcus has at least 40 species. The four most frequently encountered species of clinical importance are Staphylococcus aureus

Staphylococcus epidermidis

Staphylococcus saprophyticus. -They present as clusters which depend on the line of division (multiple planes) and we’ve talked about this before. For this type which is gram positive coccus we will study two genuses: staphylococcus and streptococcus. -If you recall that the scientific name consists of genus and species. So for example, for staphylococci, the genus is written ‘’S.’’ which stands for ‘’staphylo’’, the species is aureus, so S.aureus. -Pyogenic and pyrogenic, Pyogenic means pus القيح forming bacteria Pus: is white blood cells and their secretions like cytokines and the secretions from the bacteria. Pyrogenic: fever induced infection. -There are 40 species of staphylococci, but clinically, we are mostly concerned with those species that are pathogenic for human, and they are: *staphylococcus aureus (the most pathogenic) *Staphylococcus saprophyticus and epidermidis are considered as normal flora, but sometimes they can cause infections in the fatal or if it entered the blood stream, they may cause meningitis or septicemia or bacteremia or whatever. -According to S.aureus and other species:

In the lab we diagnose either S.aureus or S.non aureus (Staphylococcus saprophyticus or S.epidermidis). We can also make other tests to differentiate between S.epidermidis and S.saprophyticus.

ا هاي البكتيريا ذلكن احنا مبدئياُ في المختبر نعتمد في تشخيصنا في المختبر ا Aureus or non aureus.

Slide 3 … This is the shape of staphylococci, cluster-like shape, and with violet/purple gram stain color.

Slide 4 ….min 17:10 •S. aureus is coagulase positive, which differentiates it from the other species. S aureus is a major pathogen for humans. Coagulase test is the most important diagnostic criteria used to identify s.aureus from other staphylococcus species. .aureus and non aureus يعني الفحص الوحيد إلي بميزلي بين هاد الفحص نتيجته:-positive: which includes S.aureus and we call it coagulase positive S.aureus. -negative: includes S.epidermadis and S.saprophyticus and other normal human flora. •The coagulase-negative staphylococci (S. epidermidis orS. saprophyticus) are normal human microbiota and sometimes cause infection •Approximately 75% of the infections caused by coagulase-negative staphylococci are caused by S. epidermidis As we already mentioned that high proportion of nosocomial infections are caused by coagulase-negative staphylococci. •S. saprophyticus is a relatively common cause of urinary tract infections in young women. Slide 5…. Min (18:40)

Antigenic Structure

Staphylococci contain antigenic polysaccharides (Peptidoglycan) and proteins.

Since it’s gram positive means it has a piptidoglycan layer but it’s not that important as LPS

in gram negative (more virulent) but it also has consequences.

Peptidoglycan does:

• Elicits production of interleukin-1 (endogenous pyrogen)

So the endogenous pyrogen like the LPS, it induces the production of interleukin1 but in

minor amount.

•Opsonic antibodies by monocytes

An opsonin is any molecule that enhances phagocytosis.

Opsonization process: protein coating of microorganism and thus enhance

phagocytosis.

Opsonizationعوليه استصاغه

يعني كيف نخلي الخلايا اكثر استساغة لأنه يصيرلها عولية البلعوة.

Or how to make the organism more acceptable to be phagocytosed by

phagocytic cells.

•It can be a chemoattractant for PMN leukocytes

(عاهل جذب كيويائي)

In phagocytosis, the first process is attraction of WBC ‘’more specific

peptidoglycan layer attracts WBC’’

activity like-•Have endotoxin

Recall that it’s endotoxin-like, not a complete endotoxin.

•Activate complement.

.تحفز العاهل الوتون

Complements are 9 proteins in blood that complete the immune system (c1-c9)

Teichoic acids can be antigenic.

Because it’s gram positive so it contains wall teichoic acid and lipoteichoic acid

which can be antigenic also.

*antigenic means they stimulate the immune response.

Protein A is a cell wall component of S aureus strains and is a bacterial surface

protein that has been characterized among a group of adhesions. . Protein A

binds to the Fc portion of IgG molecules except IgG3.

-Most of the S.aureus contains ProteinA which is considered as an adhesion

factor, so we use coagulase and protein A in the lab for diagnosis.

S. aureus strains of clinical importance have polysaccharide capsules, which

inhibit phagocytosis. At least 11 serotypes (of capsulated) have been

identified, with types 5 and 8 responsible for the majority of infections.

There are large numbers of s.aureus without capsule but also there is part of it

capsulated.

همه من أكثر أنواع الكابسول إلي تمتلكهم البكتيريا إلي تسبب إمراضية للإنسان 8و 5

* We can diagnose these different types of capsules either by serotype or

biotype, 11 of them were diagnosed by serotype tests.

-Serotype uses serum (antigen-antibody reaction)

Since we have 11 types of capsule that means we have 11 types of antibodies

-Biotype: biochemical tests (we use enzymes, metabolism)

Slide7 … min (26:30)

Enzymes and Toxins

A. Catalase: Staphylococci produce catalase, which converts hydrogen

peroxide into water and oxygen.

This enzyme is very important because it differentiates between streptococcus

)!that they are two different genuses notice(and staphylococci

*it’s true that staphylococcus is (gram positive coccus)in clusters and

streptococcusis gram positive but in chain, but sometimes in gram stain when

students start mixing with normal saline they break the chains so it won’t

appear as clusters or chains but in growth its very clear…so we directly use

catalase to differentiate between staphylococcus which gives a positive result

for catalase and streptococcus which gives a negative results for catalase.

-The appearance of oxygen bubbles means + results.

B. Coagulase: S aureus produces Coagulase, an enzyme-like protein that clots

plasma. Coagulase may deposit fibrin on the surface of staphylococci, perhaps

altering their ingestion by phagocytic cells or their destruction within such

cells

We’ve talked about it previously, it converts fibrinogen to fibrin

*Only S.aureus shows a + result for coagulase.

*bacteria produces coagulase to hide from WBC, so it causes blood clotting and hide inside it, after while, it produces a kinase protein which lysis this clot.

Slide 8 …..Min 30:57

C. Other Enzymes

Other enzymes produced by staphylococci include a hyaluronidase, or spreading factor; a staphylokinase resulting in fibrinolysis; proteinases; lipases; and -lactamase.

*Hyaluronidas cause lysis of hyaloric acid (which is the cement substance between tissues)

-Proteinases which lysis protein.

-lipases: degrades lipids.

-Beta-lactamase:

Beta-lactame ring, presents in penicillin, so since the staphylococci contain that beta-lactamase enzyme, it lysis that ring producing no effect of penicillin, therefore we can’t use penicillin to treat staphylococci, but we can use it to treat the streptococci.

D. Hemolysins:

Hemolysin is lipids and proteins that cause lysis of RBCs and we have four types of hemolysins: alpha, beta, delta and gamma.

• a-Hemolysin acts on eukaryotic cell membranes.

Beta-Hemolysin degrades sphingomyelin and therefore is toxic for many kinds

of cells, including human red blood cells.

• Delta- Hemolysin disrupts biologic membranes and may have a role in S aureus diarrheal diseases.

• Gamma-Hemolysin is a leukocidin that lyses white blood cells

**it’s the same of Panton-valentine, causes disruption to WBCs.

E. Panton-Valentine Leukocidin

•This toxin of S aureus has two components, kill white blood cells of humans and rabbits.

Slide 9….min 33:50

F. Exfoliative toxins these epidermolytic toxins of S aureus are two distinct proteins of the same molecular weight. Exfoliative toxin A is encoded by eta and exfoliative toxin B encoded by etb these epidermolytic toxins yield the generalized desquamation of the staphylococcal scalded skin syndrome by dissolving the mucopolysaccharide matrix of the epidermis. The toxins are superantigens. G. Toxic shock syndrome toxin most S aureus strains isolated from patients with toxic shock syndrome produce a toxin called toxic shock syndrome toxin-1 (TSST-1), superantigen The toxin is associated with fever, shock, and multisystem involvement, including a desquamative skin and rash.

-These toxins are epidermolytic toxins, which means toxins that work on the epidermis. There are two types of these toxins; A and B, each one is encoded to different gene, A for eta, B for etb.

*These toxins lead to yielding the generalized desquamation (staphylococcal scalded skin syndrome, which means the removal of dermis underneath the epidermis so it separates the outer layer of skin from the layer underneath.

*تسلخ للجلديحدث

Toxic shock syndrome:

متلازمه الصدمة السمية

Is caused by the presence of toxic shock syndrome toxin-1 (TSST-1)

When the environment is suitable and the bacteria start to produce this toxin in vagina especially in females that use tampon (a special type of pads that is cylindrical inserted inside the vagina) so once the lady use this type of pads, It will create anaerobic conditions and thus enhance the production of toxic shock syndrome then it will systematically spread into the circulation and may cause heart dysfunction or kidney dysfunction so it may be fatal.

Slide 10… min (38:00)

H. Enterotoxins There are multiple (19) enterotoxins that are superantigens. The enterotoxins are heat stable and resistant to the action of gut enzymes. Important causes of food poisoning, ingestion of 25 μg of enterotoxin B results

in vomiting and diarrhea. The emetic effect of enterotoxin is probably the result of central nervous system stimulation (vomiting center) after the toxin acts on neural receptors in the gut.

enterotoxins*:سووم هعويه

Despite that exotoxins are heat labile but enterotoxins since they are superantigen are heat stable,

-About heat stable:

It’s not necessary that always exotoxins are heat labile and endotoxins are heat stable sometimes we can detect some odds to this e.g. endotoxin of E.coli is two types one is heat labile and the other is heat stable “no fixed rule for all types of bacteria”

Signs of food poisoning:

*resist the acidity of the stomach

Ingestion of 25 μg of enterotoxin B:

Bمش بالضرورة ابتلاع نوع

there are 19 type but’’ A, B, C, D, F, G’’ are the most important types.

-food poisoning is always associated with cheese contaminated with the toxin.

Slide 11… min (41:00)

PATHOGENESIS Staphylococci, particularly S epidermidis, are members of the normal microbiota of the human skin and respiratory and gastrointestinal tracts. Nasal carriage of S aureus occurs in 20–50% of humans.

Pathology: Staphylococcal lesion includes: furuncle or other localized abscess. Groups of S aureus established in a hair follicle lead to tissue necrosis (dermonecrotic factor).

تتراوح إمراضيتها ما بين

skin infection, bone infection, septicemia (local and systematic infections).

From any one focus, organisms may spread via the lymphatics and blood-stream to other parts of the body. In Osteomyelitis, the primary focus of S

aureus growth is typically in a terminal blood vessel of the long bone, leading to necrosis of bone and chronic suppuration.

Slide 12….min 42:52

empyema, ,CNS)( meningitis ,in lung)( pneumoniamay cause S aureus endocarditis, or sepsis with suppuration in any organ. Staphylococci are involved in many skin infections (e.g., acne, pyoderma, or impetigo). Scalded skin syndrome, is caused by the production of exfoliative toxins. Toxic shock syndrome is associated with TSST-1. Toxic shock syndrome is manifested by an abrupt onset of high fever, vomiting, diarrhea, myalgias, a scarlatiniform rash, and hypotension with cardiac and renal failure in the most severe cases. It often occurs within 5 days after the onset of menses in young women who use tampons, but it also occurs in children and men with staphylococcal wound infections Food poisoning caused by staphylococcal enterotoxin is

nausea, ;6)-or(1*8 hours)–characterized by a short incubation period (1vomiting, and diarrhea; and rapid convalescence. There is no fever.

Empyema is the accumulation of pus in human cavities mainly in lung.

impetigo*الحصف

: is a skin infection mainly associated with children (4-6) years old

*pyoderma: skin inflammations.

*enterotoxins are exotoxins, It depends on the target, if exotoxins work on intestine or stomach we call it enterotoxin, but if it works on cells we call it cytotoxins ,and if on nervous system we call it neurotoxins.

While endotoxin is a part of LPS in the gram negative bacteria.

Slide15 … min (47:10)

*UTI in most cases we always mean the lower UTI not the upper because the upper UNI is a complicated, and most cases of the lower UTI like urethritis and cystitis are very simple cases.

Hematogenous spread: spread of toxin through the circulatory system or lymphatic infection

DIAGNOSTIC LABORATORY TESTS

A. SPECIMENS

Surface swab pus or aspirate from an abscess, blood, tracheal aspirate, or spinal fluid for culture, depending on the localization of the process, are all appropriate specimens for testing.

The sample depend on the type of infection of its UTI then the sample is urine but if it’s pneumonia the sample is sputum , meningitis CNF, bacteremia we take blood.

B. CULTURE MEDIA

MSA., mannitol salt agar, selectiveplates, Specimens planted on blood agar

D. BIOCHEMICAL TESTS: Catalase test, coagulase test

E. SUSCEPTIBILITY TESTING AND ANTIBIOTICS (until relatively recently, MRSA was confined primarily to the hospital setting

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