Uploaded byDr. Kanwal Deep Singh Lyall
Staphylococcus
Staphylococcus is a genus of gram-positive cocci that commonly causes infections in humans. Staphylococcus aureus is one of the most important pathogenic species, able to produce several toxins and enzymes that contribute to its virulence. These include hemolysins, leukocidins, enterotoxins, toxic shock syndrome toxin, and exfoliative toxins. S. aureus can cause a variety of infections through cutaneous, respiratory, or deep tissue routes. Laboratory identification involves gram stain morphology, culture characteristics such as catalase and coagulase production, and biochemical testing. Methicillin-resistant S. aureus is an important antibiotic resistant variant.
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Staphylococcus
- 1. Staphylococcus Dr. Kanwal DeepSingh Lyall M.D. Microbiology
- 2. • Staphyle =Bunch of grapes • Kokos = berry • GPC in cluseter • Common cause of suppuration • Sir Alexander Ogston (1880) – Scottish surgeon established role in pus formation • Rosenbach – S. aureus, S. albus • Passet – S. citrus
- 3. Staphylococcus Coagulase Positive Negative S. AureusCoNs S. Epidermidis S. Hemolyticus S. Saprophyticus S. Intermedius
- 4. S. Aureus • GPCin clusters , 1µm , non-motiles, non- sporing • Divide in 3 perpendicluar planes – daughter cells remain in close proximity • Pigment : golden yellow, non-diffuseble, carotenoid, best seen at 22 – 25 C, aerobic con • ↑ed by 1% Glc. Monoacetate, milk • Grows on BA, MA, NA, MSA (selective)
- 5. Resistance • Hardy organisms •Survives in dried pus x 2 – 3 mnths • Killed @ 62 C x 30 M • Tolerates 10% NaCl • Crystal violet (1:500000) • Brilliant green (1:10 million) Lethal
- 6. Antigenic structure (CPTP) •Capsule: polysaccharide – virulence • Peptidoglycan: rigidity, complement activation, cytokine production • Teichoic acid: major Ag, adhesions & inhib of opsonisation • Protein A: chemotactic, antiphagocytic, anti- complementary, Cowan – 1 strain, binds IgG, Used for coaglutination
- 7. Toxins & Enzymes •Toxins (HLETEx) • Hemolysins • Leucocidens • Enterotoxins • TSST • Exfloiative toxin • Coagulase • Clumping factor • DNAse • Phosphatase
- 8. Toxins • Hemolysins –alpha, beta, gamma, delta – Alpha lysin – in aerobic cond., protein, inactivates @ 60 C, Reactivates @ 80 - 100 C – cytotoxic, leucotoxic, dermonecrotic – Beta lysin – lysis activated @ 37, evident on cooling • Leucocidin – PVL, slow & fast components – damages PMNs & Macrophages • Enyterotoxins – A(m/c) BC1,2,3,DEH (8) – food poisoning, nausea, vomiting, diarrhea with 6 – 8 hrs , resist boiling x 30 m, active in minute quantities, autonomic nervous system
- 10. • TSST –t , BP, vomitings, diarhoea,, rash, deaquamation, hyperemia, tampoon users • Exfoliative toxin: SSSS, Rieter’s disases – Toxin A : heat stable, chromosome coded – Toxin B: heat labile, plasmid coded
- 11. Coagulase • 8 types(A-H) • clots human/rabbit plasma • Secrerated free • Heat labile • Requires CRF • Dosent clot GP plasma • Fibrinogen fibrin • Tube test • Requires incubation Clumping factor • One type • Clumping of cocci • Bound to CW • Heat stable • Precipitation of fibrin on cell surface • Slide test • Immediate results
- 12. Pathogenesis • Cutaneous infections •Pyogenic infections • Respiratory infections • Deep seated infections • Food poisoning • Nosocomial infections • Exfoliative infections • TSST • SSSS
- 13. Lab diagnosis Sample Gram stainCulture – BA/GB/BB/MSA BACTEC 37 C x 18 – 24 hrs Colonies GS & Biochemical reactions Phage typing AST
- 14. S. aureus S.epidermidis
- 15. Biochemical reactions • Catalase+ , coagulase +, ferments mannitol, liquifies gelatin, produces phosphatase,DNAse • NA + Phen. Pthal. Diphos. Free phosphatase ammonia vapours Pink • Urease +, Indole production – ve , MR,VP + • Nitrate +ve
- 17. MRSA • Penicillinase –plasmid coded • PBP2 – Chromosome coded (mecA gene) • Resistant to all beta lactams, beta lactam + beta latamase inhb., monobactams
- 18. CoNS • S. epidermidis- Opportunistic infections • S. saprophyticus – UTI in sexually active females, resistant to Novobiocin (5µg,< 12mm) • Micrococci: Modified oxidase positive In Hugh leefson test – oxidative Tetrads Larger ( > 1 mm) White , small colonies