1 STAPHYLOCOCCUS.ppt
- 2. Introduction • Staphylococcus and Micrococcus are gram positive cocci • Other gram positive cocci includes Streptococci, Enterococcus • Presence or absence of catalase is used to divide gram positive cocci into various genera • Staphylococci and micrococcus are catalase positive.
- 4. cont • Staphylococci are similar to Micrococci in shape • But Staphylococci can be: a) pathogenic b) commensal c) Oxidative & fermentative
- 5. While Micrococci are: a) Commensal (Normal flora of skin) b) Only oxidative (Non fermentative) • Can be differentiated from Staphylococci by oxidation fermentation reactions (O – F) test
- 6. Staphylococcus Staphylococci are gram positive cocci, facultative anaerobes, catalase positive Occur in grape like clusters In Greek Staphylé =“bunch of grapes” (kokkus= grain or berry)
- 8. CLASSIFICATION: A) Based on coagulase production: 1. Coagulase positive: Eg- S. aureus 2. Coagulase negative: Eg- S. epidermidis S. saprophyticus B) Based on pathogenicity: 1. Common pathogen: Eg- S. aureus 2. Opportunistic pathogens: Eg- S. epidermidis, S. saprophyticus 3. Non pathogen: Eg- S. homonis
- 9. Staphylococcus aureus MORPHOLOGY: • These are spherical cocci. • Approximately 1μm in diameter. • Arranged characteristically in grape like clusters. • They are non motile and non sporing. • A few strains possess capsules.
- 10. Culture Media used :- i) Non selective media: Nutrient agar, Blood agar, MacConkey’s agar. ii) Selective and differential media: mannitol salt agar • Facultative anaerobes and able to grow on media containing high concentration of salt (10% NaCl) • Grow best at 35 – 37 ⁰C, but can grow 10-47⁰C.
- 11. Cultural Characteristics: i) On nutrient agar- The colonies are large, circular 2-3 mm in diameter ,convex, smooth, shiny, opaque • Most strains produce golden yellow pigments after prolonged incubation
- 12. ii) On MacConkey’s agar- The colonies are small & pink in colour. iii) On blood agar- Most strains produce β- haemolytic colonies.
- 13. Biochemical reactions: • 1) Catalase test- Positive.
- 14. 2) Coagulase test- i) Slide coagulase test- Positive. ii) Tube coagulase test- Positive. Slide coagulase test Tube coagulase test
- 15. Biochemical test • 3) DNAse thermostable nuclease that break down DNA • 4) Ferments mannitol anaerobically with acid only
- 16. Pathogenesis Source of infection: A) Exogenous: patients or carriers B) Endogenous: From colonized site Mode of transmission: A) Contact: direct or indirect( through fomites) B) Inhalation of air borne droplets
- 17. Pathogenesis Pathology depends on: • Production of surface proteins that mediate adherence of bacteria to host tissue • Elaboration of extracellular proteins such as specific toxins and hydrolytic enzymes
- 18. Virulence factors: These include A) Cell associated factors B) Extracellular factors
- 19. A) CELL ASSOCIATED FACTORS: a) Cell associated polymers b) Cell surface proteins a) CELL ASSOCIATED POLYMERS 1. Capsular polysaccharide 2. Peptidoglycan 3. Teichoic acid b) CELL SURFACE PROTEINS: 1. Protein A 2. Clumping factor (bound coagulase)
- 21. B) EXTRACELLULAR FACTORS a) Enzymes b) Toxins
- 22. a) Enzymes: 1. Free coagulase 2. Catalase 3. Lipase 4. Hyaluronidase 5. DNAase 6. Staphylokinase (Fibrinolysin) 7. Phosphatase
- 23. b) Toxins: 1. Cytolytic toxins (membrane damaging toxins Alpha haemolysin Beta haemolysin Gamma haemolysin Delta haemolysin Leucocidin (Panton-Valentine toxin) 2. Enterotoxin (8 serologically toxin) 3. Toxic shock syndrome toxin (TSST-1) 4. . Exfoliative (epidermolytic toxin)
- 24. Clinical diseases: Diseases produced by Staphylococcus aureus occurs through A) proliferation of the organisms ,leading to abscess formation and tissue destruction (infections) B) Intoxications (toxin production)
- 25. A) INFECTIONS: Mechanism of pathogenesis: Cocci gain access to damaged skin, mucosal or tissue site Colonize by adhering to cells or extracellular matrix Envade the host defense mechanisms and multiply Cause tissue damage
- 26. Common Staphylococcal infections are: 1) Skin and soft tissue: • Impetigo - localized cutaneous infection characterized by pus filled vesicle • Folliculitis- pyogenic infection in the hair follicles ( styes=eyelid) • Furuncles (boil)- large, painful, pus-filled cutaneous nodule • Carbuncles – coalescence of furuncles with extension to subcutaneous tissue
- 28. Styes Abscess
- 30. • 2) Musculoskeletal: • Osteomyelitis: destruction of the long bones, particularly the metaphyseal area • Septic arthritis: Painful erythermatous joint with collection of purulent material
- 31. 3.Respiratory infections: • Pneumonia: primarily in the very young, elderly and patients with underlying lung diseases • Empyema: occur in 10% of patients with S.aureus pneumonia 4. Cardiovascular : Bacteremia, Endocarditis
- 32. B) INTOXICATIOINS (Toxin production): • The disease is caused by the bacterial exotoxins, which are produced either in the infected host or preformed in vitro rather than direct effect of organisms. There are 3 types- • Food poisoning • Toxic shock syndrome • Staphylococcal scalded skin syndrome
- 33. 1) Food poisoning: Enterotoxin is responsible for manifestations of staphylococcal food poisoning. Eight types of enterotoxin are currently known, named A, B, C1-3, D, E, and H. It usually occurs when preformed toxin is ingested with contaminated food.
- 34. The common food items responsible are - milk and milk products, meat, fish and ice cream. Source of infection- food handler who is a carrier. Incubation period- 2 to 6 hours. Clinical symptoms- nausea, vomiting and diarrhoea. The illness is usually self limited, with recovery in a day or so.
- 35. 2) Staphylococcal Toxic shock syndrome (STSS): • STSS is associated with infection of mucosal or sequestered sites by TSST- 1 producing S.aureus. • It is fatal multi organ systems disease presenting with fever, hypotension, vomiting, diarrhoea, mucosal hyperemia and erythematous rash which desquamates subsequently.
- 36. 2 types of STSS known (staphylococcal toxic shock syndrome) i) Menstrual associated STSS: Here colonization of S.aureus occurs in the vagina of menstruating woman who uses highly absorbent vaginal tampons. ii) Non menstrual associated STSS: Here colonization of S.aureus occurs in other sites like surgical wound.
- 38. 3) Staphylococcal scalded skin syndrome (SSSS): • Exfoliative toxin produced by S.aureus is responsible for this • It is a skin disease in which outer layer of epidermis gets separated from the underlying tissues • Development of a painful rash, slough off; the skin resembles scalding
- 40. Lab diagnosis • Specimen collected depends on the type of infections discharge eg pus. - Suppurative lesion- Pus - Respiratory infection- Sputum - Bacteremia & septicemia- Blood - Food poisoning- the remains of suspected food - For the detection of carriers- Nasal swab
- 41. 1) Direct microscopy: • Direct microscopy with Gram stained smear, cocci in clusters are seen • This is of no value for specimen like sputum where mixed flora are normally present
- 42. c) Gram staining: Smears are examined from the culture plate and reveals Gram positive cocci(1μm in diameter) arranged in grape like clusters. II) Culture: a) Media used: b) Cultural Characteristics:
- 43. d) Biochemical reactions 4) Antibiotic sensitivity tests done as a guide to treatment 5) Bacteriophage typing is done for epidemiological purposes 6) Serological tests are not useful
- 44. Treatment Drug resistance is common Penicillin used to be treatment of choice, but 90% of hospital strains are resistance Resistance is due to production of Beta- lactamase enzymes. Semisynthetic penicillins ( methicillin, cloxacillin) is used against beta-lactamase producing strains Methicillin Resistant Staphylococcus aureus (MRSA) strains have become common
- 45. Treatment Currently, vancomycin is the treatment of choice for MRSA Unfortunately, isolates have now developed resistance to vancomycin.
- 46. Epidemiology • Normal flora on human skin and mucosa surfaces • Acquisition may be exogenous or endogenous • Hospital infections by staphylococci deserve special attention because of their frequency & they are caused by strains resistant to various antibiotics • Common cause of postoperative wound infection and other hospital cross infections
- 47. Prevention Spread of staphylococci from person to person is more difficult to control Proper hand washing and the covering of exposed skin surfaces MRSA also difficult to control because asymptomatic nasopharyngeal carriers are common source of infections.
- 48. Coagulase –Negative staphylococci • Catalase positive, coagulase negative, gram positive cocci arranged in clusters • Facultative anaerobes • Are opportunistic pathogens that causing infection in debilitated or compromised patients • Often colonizing biomedical devices • Includes: S.epermidis, S.saprophyticus
- 49. Staphylococcus epidermidis • Major pathogen in involving prosthetic implants such as intravascular lines or cardiac valves • Pathogenesis involves biofilm production • Endocarditis may be caused, particularly in drug addicts
- 50. Staphylococcus saprophyticus It causes urinary tract infections, mostly in sexually active young women Men are infected much less often It is one of the few frequently isolated that is resistant to Novobiocin
- 51. Distinguishing tests between S.aureus, S.epidermidis and S.saprophyticus Characters S.aureus S.epidermidis S.saprophytic us Coagulase + _ _ DNAse + _ _ Mannitol fermentation + _ _ Phosphotase + + _ Novobiocin + + _
- 52. Thank you