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Staphylococcus

Staphylococcus. Morphology. Gram-positive cocci in clusters. Staphylococcus. Streptococcus. Staphylococcus. STAPHYLOCOCCUS sp. Gram-positive cocci non motile non spore forming facultative anaerobic catalase-positive. STAPHYLOCOCCUS sp. C oagulase-negative S. epidermidis

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Staphylococcus

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  1. Staphylococcus

  2. Morphology Gram-positive cocci in clusters

  3. Staphylococcus Streptococcus

  4. Staphylococcus

  5. STAPHYLOCOCCUS sp. • Gram-positive cocci • non motile • non spore forming • facultative anaerobic • catalase-positive

  6. STAPHYLOCOCCUS sp. Coagulase-negative S. epidermidis S. Saprophyticus Coagulase-positive S. aureus

  7. S. aureus - antigenic structure

  8. Virulence Factors -Cell-Associated Capsule or slime layer (glycocalyx) Peptidoglycan (PG) Teichoic acid Protein A Clumping factor (bound coagulase)

  9. Virulence Factors: Exotoxins Hemolysins-impairment of membrane, cytotoxic to phagocytes andtissue cells Leukocidin -cytotoxic tomacrophages (Panton- Valentine L) Exfoliative toxin- serin proteases, causes blistering of skin TSST - multisystem effects Enterotoxins - vomiting, diarrhoea

  10. Virulence Factors -Extracellular Enzymes Coagulase -conversion of fibrinogen intofibrin Hyaluronidase -degradation of hyaluronicacid Staphylokinase - fibrinolysis Lipases - degradation of lipids Phospholipases- degradation of phospholipids DNAse -degradation of DNA Proteases - proteolysis

  11. Pathogenesis Acute inflammation- usually uncomplicated infection localized in portal of entry - sometimes spread generalised inf. Acute toxaemia- result of absorption of extracellular products preformed by staphylococci in the place of infection or outside

  12. S. aureus - Infections • Intoxication • Scalded skin syndrome • Toxic shock syndrome • Food poisoning Pyogenic infections • foliculitis, furunculo- sis, carbunculosis • wound infections • impetigo • abscesses • mastitis • septicaemia • osteomyelitis • pneumonia

  13. Staphylococcal inf. of oral cavity Mucosa and submucosa - sialadenitis (inflammation of parotic glands) - cheilitis angularis(inflammation of lips)- S. aureus + Candida spp. - stomatitis (inflammation of palate and tongue) Dentoalveolar abscesses, periapical abscesses Acute, chronic osteitis Osteomyelitis (mandibula) Gingivitis, periodontitis

  14. A. Pyogenic infections Skin lesions Boils Styes Furuncles(infection of hair follicle) Carbuncles (infection of several hair follicles) Wound infections (progressive appearance of swelling and pain in a surgical wound after about 2 days from the surgery) Impetigo (skin lesion with blisters that break and become covered with crusting exudate)

  15. Clinical Manifestations/Disease SKIN Folliculitis Boils (furuncles) Carbuncles • Impetigo (bullous & pustular) • Scalded skin syndrome • Neonates and children under 4 years

  16. Deep abscesses Can be single or multiple Breast abscess can occur in 1-3% of nursing mothers in pueperium Can produce mild to severe disease Other sites - kidney, brain from septic foci in blood

  17. Systemic Infections 1. With obvious focus Osteomyelitis, septic arthritis 2. No obvious focus Infective endocarditis, brain abscesses 3. Associated with predisposing factors Multiple abscesses, septicaemia (IV drug users) Staphylococcal pneumonia (Post viral)

  18. B. Toxin mediated diseases 1. Staphylococcal food poisoning Due to production of entero toxins Heat stable entero toxin acts on gut Produces severe vomiting following a very short incubation period Resolves on its own within about 24 hours

  19. 2. Toxic shock syndrome High fever, diarrhoea, shock and erythematous skin rash which desquamate Mediated via ‘toxic shock syndrome toxin’ 10% mortality rate Described in two groups of patients Associated with young women using tampons during menstruation Described in young children and men

  20. 3. Scalded skin syndrome -Also known as Pemphigus neonatorum or Ritter's disease, or Localized bullous impetigo. -Disease of young children.

  21. -Mediated through minor Staphylococcal infection by ‘epidermolytic toxin’ producing strains. -Mild erythema and blistering of skin followed by shedding of sheets of epidermis -Children are otherwise healthy and most eventually recover 3. Scalded skin syndrome

  22. Metastatic Infections • Bacteremia • Osteomyelitis disease of growing bone • Pulmonary and cardiovascular infection

  23. Laboratory Diagnosis: Direct Smear Examination Microscopic Examination Gram-positive cocci in Clusters Numerous polymorphonuclear cells (PMNs) may be seen Insert Figure 10-1

  24. Culture on blood agar • Smooth, butyrous, white to yellow, creamy • S. aureus may produce hemolysis S. aureus

  25. S. aureus – growth on blood agar - hemolysis

  26. staphylococci - growth on salt agar

  27. Identification Tests: Catalase Principle: tests for enzyme catalase 2 H2O2 2 H2O + O2 Procedure Smear a colony of the organism to a slide Drop H2O2 onto smear Observe

  28. Catalase Test: Interpretation Presence of bubbles Positive Staphylococci Absence of bubbles Negative Streptococci

  29. Catalase POS Staphylococcus Catalase NEG

  30. Identification test: slide coagulase test Differentiates members within the Staphylococci Detects clumping factor found in S. aureus Procedure Place a drop of sterile water on a slide and emulsify a colony Add a drop of plasma to the suspension Observe Agglutination = Positive No agglutination= Negative

  31. Tube Coagulase Test • Detects the extracellular enzyme “free coagulase” or staphylocoagulase • Causes a clot to form when bacterial cells are incubated with plasma • Procedure • Inoculate plasma with organism and incubate at 35-37 0 C • Observe at 30 minutes for the presence of a clot • Continue for up to 24 hours, if needed

  32. Treatment Drain infected area Deep/metastatic infections semi-synthetic penicllins cephalosporins erythromycin clindamycin Endocarditis semi-synthetic penicillin + an aminoglycoside

  33. Antimicrobial Susceptibility For non–beta-lactamase producing S. aureus • Use penicillin • Penicillinase-resistant synthetic penicillins (methicillin, nafcillin, oxacillin, dicloxacillin) Beta-lactamase producers break down the beta-lactam ring of penicillin so it inactivates antibiotic before it acts on bacterial cells

  34. Beta lactamase production – plasmid mediated Has made S. aureus resistant to penicillin group of antibiotics - 90% of S. aureus B lactamase stable penicillins (cloxacillin, oxacillin, methicillin) are used

  35. Alteration of penicillin binding proteins (Chromosomal mediated) Has made S. aureus resistant to B lactamase stable penicillins 10-20% S. aureus resistant to all Penicillins and Cephalasporins) Vancomycin is the drug of choice

  36. Prevention Carrier status prevents complete control Proper hygiene, segregation of carrier from highly susceptible individuals Good aseptic techniques when handling surgical instruments Control of nosocomial infections

  37. Coagulase-Negative Staphylococci: Staphylococcus epidermidis Predominantly hospital acquired infections Skin flora gets introduced by catheters, heart valves, CSF shunts Produces a slime layer that helps adherence to prosthetics and avoidance of phagocytosis UTIs are a common result

  38. Coagulase-Negative Staphylococci: Staphylococcus saprophyticus UTIs in young sexually active women Due in part to increased adherence to epithelial cells lining the urogenital tract Rarely present in other skin areas or mucous membranes Urine cultures If present in low amounts, it is still considered significant

  39. Coagulase-Negative Staphylococci: Staphylococcus haemolyticus Habitat: skin and mucous membranes Rarely implicated in infections Associated with wound infections, bacteremia, and endocarditis

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