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Understanding Staphylococcus Infections: Pathogenesis, Toxins, and Virulence Factors

Delve into the world of Staphylococcus bacteria, exploring their pathogenesis, toxins, and virulence factors. Learn about different Staphylococcus species, their cell wall locations, epidemiology, and associated diseases. Discover the mechanisms of immune evasion, enzymes produced, and specific toxins released by Staphylococcus. Gain insights into Staphylococcus aureus infections, systemic implications, diagnosis, treatment, and preventive measures. Unravel the complexities of opportunistic Staph pathogens and their impact on human health.

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Understanding Staphylococcus Infections: Pathogenesis, Toxins, and Virulence Factors

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  1. Staphylococcus

  2. Staphylococceae family • Low G + C • Cocci (spheres) • Grapelike clusters • 3 planes • 1 micrometer diameter • FA • Nonmotile, NSF • Halotoerant • Catalase (+) • Oxidase (-) • +/- fermentation

  3. Staphylococcus species • 61 species • Important • S. aureus • S. epidermidis • S. saprophyticus • S. pseudointermedius • Others • S. haemolyticus • S. capitus • S. hominis • S. xylosis • S. warneri

  4. Cell Wall

  5. Location • Ubiquitous • Normal flora • Skin • Mouth • Nose • Throat • Predisposing factors • Immunosuppression • Concurrent disease • AB resistance

  6. Epidemiology • Normal microbiotica • Direct transmission • Portal of Entry • Hair follicle • Break in skin • Respiratory • Complications • Bacteremia • Septecemia • Abscess

  7. Cytological Sample

  8. Pathogenesis • Immune evasion • Slime layer biofilm (microcapsule) • Evades phagocytosis • Protein A on cell wall • Binds to IgG @ Fc • Blocks opsonization • Adhesin proteins • Binds to fibrin/fibrinogen • Binds to ECM • laminin • fibronectin • collagen

  9. Enzymes • Coagulase • Catalase • Hyaluronidase • Lipase • Beta lactamase • Staphylokinase (plasminogen activator) • Proteases • DNase • FAME (fatty acid modifying enzyme)

  10. Staphylococcus Toxins • Cytolytic Toxins • Alpha = βhemolysis • Beta = sphingomyelinase • Delta • Gamma • Leukocidin = hemolysis • Leukotoxin = WBC destruction • Exfoliative toxin • ETA and ETB • Protease & esterase activity • Toxic Shock toxins • Enterotoxins (A-E)

  11. Superantigens • Enterotoxin • Food poisoning, V/D • TSS if B or C antigenic type • TSST-1: desquamation; TSS

  12. Virulence Factors Summary

  13. Staph aureus • Location • Mucous membranes • Moist areas • Diseases • Noninvasive • Food poisoning • Enterotoxin (V/D) • Cutaneous • Scalded skin • Impetigo • Folliculitis • Boils, styes, furunculosis • Systemic • Soft tissue infections

  14. Systemic Staph. aureus infections • TSS • Bacteremia • Endocarditis • Pneumonia • Meningitis • Osteomyelitis • Septic arthritis • UTI • Phlebitis

  15. Staphylococcal disease summary

  16. S. aureus • Dx • Isolation • DDx MRSA/VRSA • Tx • AB based on culture • Prevention • Wound cleansing • Hand washing

  17. MRSA • Hosptial associated • Community assoc.

  18. AMA/CDC poster

  19. VRSA vanA operon from enterococcus changes cell wall tripeptide sequence

  20. Opportunistic Staph pathogens • S. capitis • S. epidermidis • S. saprophyticus • S. xylosis

  21. S. epidermidis • Location • Normal skin flora • opportunistic pathogen • Skin/wound infections • Endocarditis • UTI • Exposure • Direct contact • Newborns • Elderly • Fomites • Catheters • Shunts • IV needles • Prosthetics

  22. S. saprophyticus • Pathogenesis • Fimbria • Adhesion proteins • Autolysins • Diseases • UTI/cystitis • Peritonitis • Enopthalmitis • Endocaritis • Septic arthritis

  23. S. xylosus • Commensal • Industry • Ferment meat • Red color of sausage • Ferment milk • Orange color of cheese • Pathogenicity • Biofilms • Enterotoxins • Disease • Nosocomial • UTI • Food poisoning (raw)

  24. S. capitis • Epidemiology • Skin microbiotica • Head predominantly • Pathogenicity • Coagulase (-) • AB resistance • Diseases • Valvular endocarditis • Neonatal septicemia • Osteomyelitis

  25. S. pseudointermedius • Animal microbiotica • Epidemiology • Zoonotic • Enterotoxins • +/- coagulase • Diseases • Pyoderma (animals) • Food poisoning

  26. Rapid Staph test

  27. Immunology • Hyperimmune serum • Capsular proteins • Surface adhesins • Vaccination • At risk population • ESRD • Dialysis patients • Premature infants • StaphVAX • Capsular proteins • Exotoxin A (Ps. Aeurginosa)

  28. Questions?

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