1 / 28

Staphylococcus

Staphylococcus. Dr. Jyotsna Agarwal Professor, Dept. of Microbiology K G Medical University, Lucknow. Family: Micrococcaceae Genus: Staphylococcus - derived from Greek “stapyle” (bunch of grapes) Include major human pathogen and skin commensals Micrococcus - skin commensal.

matthewnorton
Download Presentation

Staphylococcus

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Staphylococcus Dr. Jyotsna Agarwal Professor, Dept. of Microbiology K G Medical University, Lucknow

  2. Family: Micrococcaceae Genus: Staphylococcus- derived from Greek “stapyle” (bunch of grapes) Include major human pathogen and skin commensals Micrococcus- skin commensal

  3. Staphylococcus: General Characteristics Gram-positive spherical cells (0.5-1.5 mm) in singles, pairs, and clusters Appear as “bunches of grapes” Gram-stained smear of staphylococci from colony

  4. Non motile Non–spore-forming Nonencapsulated Catalase-producing Oxidase: negative Glucose fermenters Primarily aerobic, some facultatively anaerobic Staphylococcus: General Characteristics

  5. Approximately 33 species ~15 species associated with humans Staphylococcus divided into coagulase positive & coagulase negative categories Inhibited by high bile salt concentration Some are ß-hemolytic Colony morphology: buttery looking, cream or white colored Staphylococcus: General Characteristics

  6. S. aureus S. intermedius S. hyicus S. delphini S. schleiferi Coagulase Positive Staphylococci Human pathogens Veterinary pathogens Animal-associated species

  7. Primary pathogen Habitat: anterior nares (carriers) Colonization: axilla, perineum, pharynx Produce superficial to systemic infections Mode of transmission: Pus formation Staphylococcus aureus

  8. Natural history of disease • Usual sites - skin, nasopharynx, perineum • Breach in mucosal barriers - can enter underlying tissue • Characteristic abscesses with Pus • Bacteria liberates toxins-

  9. Due to direct effect of organism Local - skin Deep abscesses Systemic infections Toxin mediated Food poisoning toxic shock syndrome Scalded skin syndrome DISEASES

  10. Pathogen Factors ENZYMES Catalase (counters host defences) Coagulase Hyaluronidase Lipases B lactasamase (antibiotic resistance) TOXINS- enterotoxin, TSST, epidermolytic toxin Virulence Factors of S. aureus

  11. SKIN LESIONS- superficial • Boils • Styes • Furuncles • Carbancles • Wound infections

  12. DEEP ABSCESSSES • Direct / by blood • Can be single / multiple • Eg. - Breast abscess kidney, brain, Osteomyelitis, septic arthritis

  13. TOXIN MEDIATED DISEASES 1. Staphylococcal food poisoning • Due to production of enterotoxins • preformed toxin, heat stable • short incubation period • Milk & milk products

  14. 2. Toxic shock syndrome • High fever, diarrhoea, shock and erythematous skin rash which desquamate • Mediated via ‘toxic shock syndrome toxin’ • 10% mortality rate

  15. 3. Scalded skin syndrome • Disease of young children • Mediated through minor Staphylococcal infection by ‘epidermolytic toxin’ producing strains • Good prognosis

  16. Virulence Factors: Extracellular enzymes Cytolytic Toxins Alpha hemolysin: lyses rbcs, damages plts, causes severe tissue damage ß hemolysin: acts on sphingomyelin in the plasma membrane of rbcs

  17. Virulence Factors: Extracellular enzymes Hyaluronidase: Hydrolyzes hyaluronic acid in connective tissue allowing spread of infection Staphylokinase: fibrinolysin which allows spread of infection Coagulase: virulence marker Lipase: allows colonization

  18. Beta-lactamase or Penicillinase: confers resistance DNase: degrades DNA Protein A: in cell wall, it binds to Fc part of IgG toblock phagocytosis Virulence Factors: Extracellular enzymes

  19. Coagulase-Negative Staphylococci Habitat: skin and mucous membranes Common human isolates S. epidermidis S. saprophyticus

  20. Coagulase-Negative Staphylococci: Staphylococcus epidermidis Virulence factor: “slime” Mode of infection: colonization of medical implants Infections are acquired nosocomially Serious infections among immunosuppressed patients or neonates may occur

  21. Habitat: skin and mucosal membranes of the genitourinary tract Common cause of urinary tract infections in young, sexually active females Coagulase-Negative Staphylococci: Staphylococcus saprophyticus

  22. Microscopic Examination Gram-positive cocci pairs and clusters Numerous polymorphonuclear cells (PMNs) Laboratory Diagnosis: Direct Smear Examination

  23. Laboratory Diagnosis: Cultural Characteristics Colony morphology Smooth, butyrous, white to yellow, creamy Grow well in 18-24 hours S. aureus may produce hemolysis on blood agar S. aureus

  24. Principle: tests for enzyme catalase Drop H2O2 onto smear Bubbling = POS (Staph) No bubbling = Streptococci Identification Tests: Catalase

  25. Cell-bound “clumping factor” converts fibrinogen to fibrin which precipitates on cell causing agglutination Extracellular enzyme “free coagulase” Identification Tests: Coagulase Test • Two methods • Slide test: screens for “clumping factor” • Tube test

  26. Novobiocin Susceptibility Test Test to differentiate coagulase-negative staphylococci from S.saprophyticus from urine samples S. saprophyticus is resistant (top)

  27. Beta-lactam group of antibiotics- (penicillins, cloxacillins, ampicillin, amoxycillin) Beta-lactamase producers treatment of choice Amoxyclavulinic acid or ampicillinn sulbactam combo or methicillin/ oxacillin For methicillin -resistant S. aureus(MRSA) treatment of choice- Vancomycin Antimicrobial Susceptibility

  28. Summary • Characters of Staphylococcus aureus • Enzymes / Toxins • Infections / Diseases • Laboratory diagnosis • Treatment / Abx resistance

More Related