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Staphylococcus
1. Staphylococcus are Gram-positive cocci that occur in clusters and can cause a variety of infections through toxins or direct invasion. Common species include S. aureus, S. epidermidis, S. saprophyticus. 2. S. aureus is an important human pathogen capable of causing skin infections, pneumonia, sepsis and toxic shock syndrome. Virulence factors include coagulase, hemolysins and enterotoxins. 3. Laboratory diagnosis involves culturing specimens on selective media, testing for catalase and coagulase production, and antibiotic susceptibility testing. MRSA strains are resistant to multiple
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Staphylococcus
- 1. Staphylococcus Asmabanu Shaikh Tutor Department ofMicrobiology PIMSR
- 2. What are Staphylococcus •Sir Alexander Ogston, a Scottish surgeon, first showed in 1880 that a number of human pyogenic diseases were associated with a cluster- forming micro-organism. He introduced the name 'staphylococcus’ • (Greek: staphyle = bunch of grapes; kokkos = grain or berry), now used as the genus name for a group of facultatively anaerobic, catalase-positive, Gram-positive cocci.
- 3. Classification • Family • Genus •Species Micrococcaceae Micrococcus and Staphylococcus S. aureus S. saprophyticus S. epidermidis M. luteus
- 4. The genus Staphylococcuscontains about forty species and subspecies today. • Only some of them are important as human pathogens: • Staphylococcus aureus • Staphylococcus epidermidis • Staphylococcus hominis • Staphylococcus haemolyticus • Staphylococcus saprophyticus • others
- 5. Morphology • Gram-positive cocci,nonmotile, facultative anaerobes • Cells occur in grape like clusters because cells division occurs along different planes and the daughter cells remain attached to one another
- 6. Pathogenicity and virulence •Two types of disease: • Infections • Intoxications
- 7. INFECTIONS • Cocci gainaccess to damaged skin, mucosal or tissue sites • Colonise by adhering to cells or extracellular matrix • Evade host defence mechanisms • Multiply and cause tissue damage INTOXICATION • Caused by bacterial toxins – produced either in the infected host or preformed in vitro
- 8. Virulence factors CELL-ASSOCIATED POLYMERS •Cell wall polysaccharide peptidoglycan • Techoic acid – antigenic component of the cell wall • Capsular polysaccharide CELL SURFACE PROTEINS • Protein A (present in most S. aureus strains Biological properties – chemotactic, anti-phagocytic and anti-complementary effects Induces platelet damage and hypersensitivity) • Clumping factor –‘bound coagulase’ (responsible for slide coagulase)
- 9. EXTRACELLULAR ENZYMES 1) Coagulase(An enzyme that brings about clotting of human or rabbit plasma Acts with a coagulase reacting factor (CRF) present in plasma Binds to prothrombin Converts fibrinogen to fibrin Basis of tube coagulase test) 2) Lipid hydrolases or lipases 3) Hyaluronidase 4) Nuclease 5) Protein receptors Virulence factors
- 10. Toxins Cytolytic toxin: - Membraneactive substance. - Consising of four haemolysins – alpha, beta, gamma, delta and leucocidin. Enterotoxin : - Responsible for manifestations of Staphylococcal food poisoning – nausea, vomiting and diarrhea -2–6 hours after consuming food contaminated by preformed toxin - Meat, fish, milk and milk products contaminated with staphylococci, toxin accumulates - Source of infection – food handler - Disease – self-limited - Tests to detect toxin – ELISA, latex agglutination
- 11. TOXIC SHOCK SYNDROMETOXIN(TSST) – a potentially fatal multisystem disease, presenting with fever, hypotension, myalgia, vomiting, diarrhea, mucosal hyperemia and an erythematous rash EXFOLIATIVE TOXIN • Exfoliative (epidermolytic) toxin, also known as ET or ‘exfoliatin’, responsible for staphylococcal scalded skin syndrome (SSS) • SSS is an exfoliative skin disease • The outer layer of the epidermis becomes separated from the underlying tissues
- 12. Clinical Manifestations Skin &Soft tissue infections • Folliculitis, Furuncle • Carbuncle, Impetigo • Mastitis and breast abscess • Surgical site wound infections • Cellulitis
- 13. Clinical Manifestations... Musculoskeletal Infections • Septicarthritis • Osteomyelitis • Pyomyositis in HIV • Psoas abscess • Epidural abscess Respiratory Tract Infections • Ventilator associated pneumonia in adults • Septic pulmonary emboli • Post viral pneumonia • Empyema and Pneumothorax • Pneumatocele in neonates
- 14. Bacteremia and itsComplications • Sepsis, septic shock • Central line associated blood stream infection • Metastasis - kidney, joints, bone and lung • Native-valve endocarditis • Prosthetic-valve endocarditis • Intravenous drug use associated endocarditis
- 15. Clinical Manifestations UTI(Urinary tract infection)-secondary to bacteremia Toxin-Mediated Illnesses • Toxic shock syndrome • Food poisoning • Staphylococcal scalded- skin syndrome Infections Associated with CA-MRSA • Necrotizing pneumonia • Purpura fulminans • Necrotizing fasciitis
- 16. Epidemiology • Staphylococci –primary parasites, human beings and animals • Colonise – skin, skin glands and mucous membranes • Source of infection – human patients and carriers • Patients with superficial infections and respiratory infections disseminate large number of staphylococci into the environment • Healthy persons • 10–30% carry staphylococci in the nose • 5–10% in the vagina • Colonisation of umbilical stump – common • Some carriers, called shedders, disseminate large numbers of cocci for prolonged periods
- 17. • Staphylococcal diseasemay follow endogenous or exogenous infection. • Mode of transmission: • Contact – direct/fomites • Dust • Airborne droplets Methicillin resistant S.aureus (MRSA) • Hospital infections – frequency – strains resistant to a variety of antibiotics • Post-operative wound infections and hospital cross-infections • Resistant to all beta lactam antibiotics and other antimicrobial agents
- 18. OUTBREAK CONTROL MEASURES •Isolation of patient with open staphylococcal lesion • Detection of staphylococcal lesions among surgeons, nurses and other hospital staff and keeping them away from work till lesions heal • Strict asepsis in operation theatre • Hand washing – simplest and most effective method • Search for carriers among hospital staff • Carriers treated with local application of mupirocin or chlorhexidine
- 19. LABORATORY DIAGNOSIS. 1) Specimen 2)Microscopy 3) Culture 4) Identification 5) Serological tests
- 20. LABORATORY DIAGNOSIS.. Infection Specimen Suppurativelesion Pus, wound swab Respiratory Infections Sputum Urinary tract infection Mid stream urine PUO, Bacteremia Blood Food poisoning Feces, vomitus, food Carriers Nasal & perianal swab
- 21. LABORATORY DIAGNOSIS. • MICROSCOPY •Gram staining -Gram positive cocci in clusters, non capsulated, non sporing.
- 22. LABORATORY DIAGNOSIS- CULTURECHARACTERISTICS • Aerobe, facultative anaerobe, Non- fastidious • Nutrient agar – Golden yellow • Blood agar – beta hemolytic
- 23. LABORATORY DIAGNOSIS- CULTURECHARACTERISTICS • MacConkey agar- Small pink • Liquid medium - uniform turbidity • Selective media - Mannitol salt agar – yellow colonies -mannitol fermentation - Salt milk agar - Ludlam’s medium
- 24. Biochemical Tests Coagulasetest o Tube coagulase o Clumping factor Heat stable thermo nuclease test DNase test Phosphatase (also produced by S.epidermidis) Golden yellow pigmentation Hemolysis on blood agar Mannitol fermentation Black coloured colonies on potassiumtellurite agar Gelatin liquefaction Protein A detection • S.aureus positive and CONS mostly negative
- 25. Catalase test : Procedure: • Take clean glass slide • Put a drop of 3 % hydrogen peroxide • Add bacterial colony • Result: If bubbles is formed, test is positive
- 26. Coagulase test : •Tube coagulase test – detects free coagulase • 0.1 ml of broth culture added to 0.5 ml of human or rabbit plasma, positive and negative controls are set up • Incubated – water bath at 37°C for 3–6 hours • If positive, plasma clots and does not flow when the tube is tilted
- 27. TUBE COAGULASE TEST Tubecoagulase test: positive, negative
- 28. • Slide coagulasetest – detects bound coagulase • The isolate is emulsified in a drop of saline on a slide • A drop of human or rabbit plasma is added and mixed • Positive and negative controls are set up • Prompt clumping indicates a positive test
- 29. Tube coagulase Slidecoagulase Due to coagulase enzyme Due to clumping factor Requires CRF in plasma Does not require CRF in plasma Done in tube Done in slide Positive if clot is formed Positive if clumps are formed Coagulase enzyme has eight serotypes Clumping factor has one serotype S.Lugdunensis gives a negative result S.Lugdunensis gives a positive result Both tube and slide coagulase positive for S.aureus, S.hyicus, and S.intermedius
- 30. Antibiotic sensitivity tests–important –drug resistance Zone of inhibition around antibiotic discs on the lawn culture of test bacteria
- 31.
- 32. CONS • Mostly harmlesscommensals • Less virulent than S.aureus • Recently their role as pathogens is increasingly been reported • Important species: - S. epidermidis - S.saprophyticus - S.lugdunensis - S.schleiferi
- 33. STAPHYLOCOCCUS EPIDERMIDIS • Mostcommon CONS (75-80%) • Normal flora - skin, oropharynx and vagina • Risk - prosthetic devices • Pathogenesis- - Initial adhesion - Colonization (Biofilm)
- 34. STAPHYLOCOCCUS EPIDERMIDIS • Infections: -Prosthetic-device related infections endocarditis with insertion of valvular prosthesis and ventricular shunt infections - Stitch abscess
- 35. CoNS.. Staphylococcus saprophyticus • UTIin sexually active young women • Unlike other Staphylococci resistant to novobiocin • S.lugdunensis and S.schleiferi - Native-valve endocarditis and osteomyelitis
- 36. Treatment • Drug resistance– appropriate antibiotic based on antibiotic sensitivity tests • Benzyl penicillin – most effective if strain is sensitive • Cloxacillin used against penicillinase-producing strains • MRSA – resistant to all beta lactum antibiotics • Life-threatening staphylococcal infections – vancomycin – drug of choice • Mild superficial infections – topical applications – bacitracin, chlorhexidine or mupirocin • Carriers – local application – mupirocin
- 37. QUESTIONS : • Describemorphology, culture characteristics and laboratory diagnosis of Staphylococcus. • Describe pathogenesity and and laboratory diagnosis of Staphylococcus. • Full form : MRSA, VRSA, TSST, SSS