Staphylococci DON XAVIER N.D

 Cocci.  Gram positive.  Non motile.  On NA they form pigmented colonies.  Haemolytic.  Enzyme production.  Ferment sugar with acid production.

VIRULENCE FACTORS CAPSULE PEPTIDOGLYCAN LAYER PROTEIN A TECHOIC ACID CLUMPING FACTOR

 ALPHA TOXIN  BETA TOXIN ( Sphinghomylinase)  DELTA TOXIN  GAMMA TOXIN  LEUKOCIDIN (F & S Subunit)  EXOFOLIATIVE TOXIN  TSST 1 ( PYROGENIC EXOTOXIN C ENTEROTOXIN F)  ENTEROTOXIN STAPHYLOCOCCAL ENZYMES  COAGULASE  CATALASE  HYALURONIDASE  FIBRINOLYSIN  LIPASES  NUCLEASES  PENINCILNASE MEMBRANE DAMAGING TOXINS

 CULTURE Selectively Isolated on 7.5% NaCl & Mannitol - Fermented by S. aureus.  Blood Agar Show Haemolysis by cytotoxins  Coagulase Test Tube Coagulase 0.1 ml young broth /culture /agar 0.5ml plasma edta added to stop coagulation Incubate at 37’c for 3- 6 hrs +ve Plasma Clots, if kept longer clot disappear by ac’n of fibrinolysin Slide coagulase isolate +plasma+ saline

 Phage typing (pattern method) - based on susceptibility to bacteriiophages strain to be typed inoculated in nutrient agar Phages are applied over marked squares in fixed dose (Routine Test) Overnight incubation Lysed by some phages, counted and typed on basis of squares lysed

streptococcus

Gram positive Catalase negative Cocci arranged in chains Non motile Non-sporing Capsulated. Pathogenic forms causes pyogenic(pus forming) lesions. Some are capnophilic & fastidious in nature

Beta - haemolytic Causes primary infections in man Zone of clear haemolysis in blood agar Classified on basis of carbohydrate antigen on cell wall Caused by streptolysin O& S Alpha - haemolytic No zone of haemolysis Greenish discoloration of agar Part of normal flora Opprtunistic infections Gamma - haemolytic No change in medium Indifferent streptococci Enterococcus group

VIRULANCE FACTOR 1.Capsular Hyaluronic acid 2. Cell wall polysaccharide 3. M protein 4.F protein 5.Pyogenic exotoxins  PATHOGENIC ROLE  Non immunogenic,antiphagocytic  Responsible for non suppressive sequele of streptococcal infections  Antiphagocytic, degrades C3b.  Mediates adherans to epithelial cells.  Mediates pyrogenicity, enhacment of delayed hypersensitivity, suscepibility to endotoxins, cytotoxicity, mitogenecity for t cells,B cell function suppression.

 6. Streptolysin S  7. Streptolysin O  8. Streptokinase  C5a peptidase  DNAse  Lyses leucocytes, erythrocytes, and platelets, immunogenic stimulates release of lysosomal enzymes  Facilitates spread of infection in tissues, lyses blood clot.  Degrades C5a  Depolymerises cell-free DNA in purulent material.

Microscopy Cocci in chain associates with leukocytes. culture PIKE’S Medium (1/ crystal violet +1/16000 sodium azide),SHEEP Blood agar for primary isolation. Bacitracin test For identificat’n of s.pyogens Bacitracin – isolated from b.subtilius, distrupts cell wall & peptidoglycan syn’s. Test filter paper disc (0.04 u)+sheep blood agar Wide zone of inhibition in s.pyogens area only

Latex agglutination test Principle - Based on presence of group specific carbohydrate Test A g extracted by treating specimen with nitrous acid for 5 min extract is neutralised mix with bound ab’sin filter membrane or latex particles Colour change in eia /agglutination in latex Positive result Aso test is also similar in method but ab against streptolysin o is measured.

Camp test