Staphlococcus Flashcards
Family
Micrococcaceae
Important species
S.aureus,
S. epidermidis, and
S. saprophyticus
Epidemiology
Normal flora of skin and na so pharynx
Microbiology
Gram positive cocci in clusters, (Staphyle=bunch/grape-like); S. aureus (aureus=gold), on sheep blood. They are catalase positive.
G+ve cocci
-Catalase test+
Streptococcus Staph/Micrococcus
-VP test.+
Micrococcus Staphylococcus
-Coagulase test+
CNS Staph aureus
S 5ug Novobiocin R
•Staph. Epidermidis. Staph.saprophyticus.
Protein A
-It binds the Fc portion of IgG and thus protects the organism against opsonisation & phagocytosis
Coagulase
-It leads to fibrin formation around the bacterium and protects it as in No1 above.
Haemolysins (4 types).
They are Toxins that destroy RBCs, Neutrophils, Macrophages & Platelets.
Alpha
Beta
Gamma
Delta
Alpha Toxin (or haemolysin)-
causes critical necrosis. Lysis rabbit sheep,& cat RBCs and rabbit & human WBCs.
Beta Toxin (or haemolysin)
Lysis sheep,human and Ox RBCs.
Delta Toxin (or haemolysin)
Lysis RBCs and WBCs of all animals.
Gamma Toxin (or haemolysin
acts like delta haemolysin.
Enzymes produced by Staphylococci.
- Coagulase.
•2. Phosphatase.
•3.Dnase
•4. Hyaluronidase.
•5. Staphylokinase.
•6. Lipase.
•7. Gelatinase
Nb
Only Coagulase is unique to S.aureus; all other enzymes are produced by other species of Staphylococci.
Enterotoxins.
- Five types exist: A-E.
•Types A & D-are associated with food poisoning.
•Types C & E are associated with TSS.
Exfoliatin
also called epidemolytic or exfoliative toxin, is reponsible for SSS (Scalded skin syndrome).
Coagulase test:
a) Slide test: For bound coagulase.
•b) Tube test: For free& bound coagulase.
Diseases caused by direct organ invasion by S.aureus.
- Pneumonia.
•2.Meningitis.
•3. Osteomyelitis.
•4. Acute bacterial endocarditis.
•5. Septic arthritis.
•6. Skin infections: (Abscesses,boils, carbuncles,furuncles, impetigo etc).
•7. Bacteraemia/sepsis.
•8. UTI by both S.aureus & S. saprophyticus.
Diseases caused by exotoxins.
- Gastroenteritis.
•2. TSS-Toxic shock syndrome due to TSST-1 (Tampon associated).
•3. Scalded skin syndrome-SSS-by exfoliative toxin A & B.
Miscellaneous issues about Staphylococci.
•1. MRSA & VRSA.
•2. All Staphylococci are notorious for HAIs.
•3. Beta-haemolysis.
•4. Golden yellow colonies.
•5. Mannitol salt agar.
•6. SE-associated with prostheses infections.
•7. SS-associated wit UTI in sexually active women.
Treatment
- Penicillinase-resistant penicillins like Nafcillin,dicloxacillin.
•2. Clindamycin.
•3. Vancomycin.
•4. Linezolid.
•CONTROL:
Strict personal & community hygiene.
