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Staphylococci ( gram positive cocci)
- 3. GRAM “+”TIVE COCCI By SYEDA MARYAM
- 5. DISEASES CAUSED • Abscess • Various pyogenic infection ENDOCARDITIS, OSTEOMILITIS etc • Food poisoning • Scalded skin syndrome • Toxic shock syndrome • Hospital acquired PNEUMONIA • Septicemia and surgical wound infection • Skin and soft tissue infections FOCILITIS, CELULITIS, IMPETIGO • Most common cause of BACTERIAL CONJUNCTIVITIS
- 7. • Microscopically grape like structure • CATALASE important virulence factor enable bacteria (staphylococcus) to survive killing effect within neutrophil not produced by STREPTOCOCCUS CATALASE + • Ferments MANITOL H2O2 H2O O2
- 8. • COAGULASE produced only by S. aureus causes plasma to clot PROTHROMBIN THROMBIN FIBRINOGEN FIBRIN coagulase
- 9. • STAPHYLOXANTHIN carotenoid pigment impart golden color to colonies enhance pathogenicity inactivates effect of ROS( H2O2 ) • HEMOLYSIN only produced by S. Aureus hemolyse RBCs source of IRON used to produce CYTOCHROME Generates energy
- 10. • BETA- LACTAMASE produced by plasmid present in 90% of S. Aureus resists many but not all penicillin i.e. METHICILLIN NAFCILLIN some strains of S. Aureus are resistant even to beta lactamase resistant penicillin due to mutations in PBPs MRSA NRSA
- 11. IMPORTANT STRUCTURES OF S. AUREUS• Protein A major protein in cell wall imp. Virulence factor bind the Fc portion of IgG at complement binding site preventing activation of complement cascade no C3b produced opsonization is reduced phagocytosis is reduced • TECHOIC ACID polymer of ribitol phosphate mediate adherence of S. Cocci to mucosal membranes • LIPOTECHOIC ACID has role in production of septic shock by producing CYTOKINES i.e. IL-1 TNF
- 12. • MICROCAPSULE small amount of polysaccharide capsule around S. aureus poorly immunogenic difficult to form effective vaccines • PEPTIDOGLYCAN of S. Aureus has endotoxin like property produces CYTOKINES activation of coagulase and complement cascade can cause clinical finding of septic shock yet not posses endotoxin
- 13. HUMAN RESERVOIR FOR S. AUREUS • Nose is main site of colonization • Skin common site of S. aureus esp. in hospital personnel and patients hand contact imp. Mode of transmission • Vagina in 3% of women predisposes Toxic shock syndrome • Additional sources are human lesion fomites contaminated by these lesions i.e. towel
- 14. CONDITIONS WHICH PREDISPOSES TO S. AUREUS INFECTIONS• Reduced humoral immunity including low level of antibodies neutrophils complement • Diabetes • Intravenous drug usage • CGD ( chronic granulomatous disease ) defected neutrophils unable to kill bacteria
- 15. PATHOGENESIS by inducing PYOGENIC INFLAMMATION by TOXINS PRODUCTION ENTEROTOXIN TSSTEXFOLIATIN P-V LEUKOCIDIN
- 16. PYOGENIC INFLAMMATION• Typical lesion of S. aureus infection is an ABSCESS • Abscess undergoes central necrosis usually drain to outside FRUNCLES and BOILS organism may disseminate via blood stream as well • Foreign bodies are important predisposing factor sutures intravenous catheter
- 17. ENTEROTOXIN• Causes food poisoning watery and non bloody diarrhea prominent vomiting caused by cytokines released by lymphoid cells stimulates action of enteric nervous system to activate vomiting center of brain • Act as super antigen within GIT stimulates release of large amount of IL-1, IL-2 • Fairly heat resistant not inactivated by brief cooking • Resistant to acid and enzyme of stomach and jejunum • Six immunologic types of enterotoxin from A-F
- 19. TOXIC SHOCK SYNDROME TOXIN (TSST) • Is a super antigen • Cause toxic shock syndrome in individuals with wounds patients with nasal packing release of large amount of IL-1 and TNF • Locally produced by S. aureus present in vagina , nose and other infected sites • Toxic enters in blood stream TOXEMIA • Occurs in people who don’t have antibody against TSST TREATMENT • Correction of shock by using fluid pressor drugs , inotropic drugs • Administration of beta lactamase resistant penicillin i.e. Methicillin • pooled serum globulin which contain antibody against TSST
- 21. EXFOLIATIN • Cause scalded skin in young children • Is epidermolytic • Act as a protease cleaves desmoglein present in • desmosomes separation of epidermis from granular cell layer
- 22. TREATMENT • 90% or more of S. Aureus strains are resistant to penicillin • I can be treated with Beta lactamase resistant penicillin vancomysin cephalosporin • 20% of S. aureus strains are MRSA methicillin resistant NRSA nafcillin resistant resistance is due to mutations in PBPs drug of choice vancomysin + gentamysin ( some times added) daptomycin
- 24. • S. epidermidis is coagulase negative • Doesn’t produces exotoxin • Doesn’t cause food poisoning toxic shock syndrome • Causes pyogenic infections particularly on intravenous catheter prosthetic implants heart valves prosthetic joint (hip joint) vascular graft
- 25. • Part of normal human flora on skin and mucous membrane • can enter blood streams BACTEREMIA can cause metastatic infection esp. at the site of an implant • Infections are almost always hospital acquired • Major cause of sepsis in neonates • Cause of peritonitis in patient with renal failure who are under going peritoneal dialysis
- 26. • Most common bacterium to cause CSF shunt infection • Produce glycocylex which enables to adhere to prosthetic implant materials • Doesn’t produce hemolysin Non Hemolytic • Doesn’t produce STAPHYLOXANTHINE white colonies
- 28. • S. saprophyticus is coagulase negative • Doesn’t produces exotoxin • Doesn’t cause food poisoning toxic shock syndrome • Found in mucosa of genital tract in young women • Infection almost always Community acquired
- 29. • 2nd to E. coli as a cause of community acquired UTI in young women • Doesn’t produce staphyloxanthin white colonies • Doesn’t produce hemolysin non hemolytic • Causes pyogenic infections esp. Urinary tract infection in young CYSTITIS women
- 30. PREVENTION • No vaccine against staphylococci • Control of S. aureus spreading by frequent hand washing aseptic management of lesion cleanliness • Nasal colonies of S. aureus is reduced by oral antibiotics CIPROFLOXACIN etc. intranasal mupirocin but difficult to eliminate completely • CEFAZOLIN often used preoperatively to prevent staphylococcal surgical wound infections
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