Staphylococcus aureus overview of SlideShare

A detailed summary about staphylococcus aureus

1. VIVEKANANDHA ARTS AND SCIENCE COLLEGE FOR WOMEN VEERCHIPALYAM-637303,SANKAGIRI,SALEM Dt.,TAMILNADU,INDIA. AFFILIATED TO PERIYAR UNIVERSITY,SALEM;RECOGNISED UNDER SECTION 2(F)&12(B) OF THE UGC ACT 1956) SUBJECT INCHARGE; Dr.R.MYTHILI; HEAD OF THE DEPARTEMENT, Assistant professor, Department of Microbiology, VIAAS,Sankagiri. DEPARTMENT OF MICROBIOLOGY SUBJECT : MEDICAL BACTERIOLOGY SUBMITTED BY; DHARANIPRIYA SELLAPPAN, III B.SC.MICROBIOLOGY, DEPARTMENT OF MICROBIOLGY, VIAAS,Sankagiri. TITLE : STAPHYLOCOCCUS AUREUS

2. INTRODUCTION FAMILY = MICROCOCCAE ( Consist of gram positive cocci arranged in tetrads and clusters ) GENUS = STAPHYLOCOCCUS Term “ Staphylococcus “ derived from Greek , Staphyle = bunch of grapes and Kokkos = berry, meaning bacteria occurring in grapelike clusters or berry .

3. HISTORY ROBERT KOCH (1878) first to se staphylococcus in pus specimen . LOUIS PASTEUR (1880) first to cultivate in liquid medium . SIR ALEXANDAR ONGSTON (1881) named the bacteria as ‘ staphylococcus’.

4. definition Staphylococci are gram positive cocci arranged in grape like clusters. Ubiquitous and commonest cause of localized suppurative lesion . Has the tendency of developing resistance to penicillin and other antibiotics very easily. Medically important species are staphylococcus aureus , staphylococcus epidermidis, staphylococcus sapropbyticus .

5. morphology Gram positive cocci arranged in grape like clusters. Non motile. Non sporing. Approx. 1mu in diameter culture characteristics Grow readily on ordinary culture media. Optimum temp 37 c

6. Optimum ph 7.4 – 7.6 Aerobes and facultative anaerobes. culture characteristics: Nutrient agar : Colonies are 2-4 mm dia, circular , smooth ,convex ,opaque ,easily emulsifiable . Most of the stains produce golden yellow pigment . On slope – ‘Oil Plant ‘ appearance .

7. ON BLOOD AGAR – Beta hemolysis colonies . ON MAC CONKEY – Lactose fermenting pink colonies, SELECTIVE MEDIA – Contain 8-10% NaCl , lithium chloride , tellurite and polymyxin . MANNITOL SALT AGAR – Yellow colonies – Mannitol fermentation LIQUID MEDIUM – Uniform turbidity .

8. BLOOD AGAR MANNITOL SALT AGAR LIQUIDE MEDIUM

9. BIOCHEMICAL REACTIONS Catalase positive ; oxidase negative Ferment glucose, lactose, maltose , sucrose , and mannitol with production of acid but no gas . Mannitol fermentation carries diagnosis significance Most strains are lipolytic and hence produces dense opacity when grown on media containing egg yolk . Indole test = negative MR test = positive

10. VP test = Positive Urease test = Positive Hydrolyse gelatin Reduces nitrate to nitrite Phosphate = positive DNA ase test = Positive Coagulase test = Positive

11. pathogenic strain & Non pathogenic strain – differences Beta hemolysis on blood agar . Production of golden yellow pigment . Coagulase production . Mannitol fermentation . Gelatin liquefaction . Production of enzyme deoxyribonuclease . Tellurite reduction .

12. Antigenic structure : Capsule Peptidoglycan Teichoic acid Protein A TOXINS: Hemolysis toxins : Alpha , Beta , Gamma , Delta . Leucocidin , Epidermolytic toxins , Enterotoxins , Toxic shock syndrome toxin.

13. Extracellular enzymes COAGULASE : 8 antigenic type : A-H, mostly A . Has property to clot human or rabbit plasma . Activates coagulase reacting factor ( CRF ) present in the plasma , converts fibrinogen to fibrin and clots the plasma . May coat the organism and prevents opsonisation and phagocytosis . Free coagulase tube coagulase test . Bound coagulase slide coagulase test .

14. Pathogenicity About 30 – 50 % of adults carry staphylococcus aureus in anterior nares and perineum , axillae , vagina Mode of transmission is by contact, fomites or by droplets . Enters the body through damaged skin, mucous membranes and following viral infection ( esp. LRTI ) Diseases of Staph. Aureus are divided into TOXIN MEDIATED and due to INVASION . 01. CUTANEOUS INFECTIONS : Pustules, boils, carbuncles, abscesses, styes , impetigo,wound , and burn infection.

15. 02. DEEP INFECTIONS Osteomyelitis, tonsillitis, pharyngitis, sinusitis, endocarditis, meningitis, bacteriaemia, septicemia . 03. FOOD POISONING : Heat stable toxin – 100c for 10 to 40 min. Nausea, vomiting and diarrhea occurs 2to 6 hours after consuming performed toxin. Cooked meat, fish, milk, and milk products are mostly responsible. Self limiting Neutralized by specific antitoxin. Detection by latex agglutination and ELISA .

16. 04. EXFOLIATIVE DISEASES : Epidermolytic toxin Stripping superficial layers of epidermis from underlying tissue blister formation . Most dramatic disease is scalded skin Syndrome or Ritter’s disease mostly seen in newborns and previously healthy children . 05. TOXIC SHOCK SYNDROME : Potentially multisystem disorder with fever, hypotension, myalgia, rash, vomiting, diarrhea, etc., Important cause of nosocomial infection .

17. First seen in children and adolescent in 1978 but widely known after an outbreak in menstruating women using absorbent vaginal tampons which was heavily colonised by Staph. Aureus in USA in 1980 . 05. STAPHYLOCOCCAL FOOD POISONONG : Caused when consuming food in which staphylococcus aureus has multiplied and formed endotoxin . SYMPTOMS: Nausea Vomiting Severe abdominal cramp

18. Diarrhea sweating Headache etc., MODE OF TRANSMISSION : Person with lesions Airborne droplets Asymptomatic carrier Cross infection PREVENTION: Wash your hands

19. Keep wounds covered Reduce tampon risks Avoid sharing personal care items Cooking and storing food properly TREATMENT AND DRUGS Antibiotic therapy Wound drainage Device removal Removal of dead tissue

20. LABORATORY DIAGNOSIS A. HEMATOLOGICAL INVESTIGATION : 01. TLC ( TOTAL LEUKOCYTE COUNT ) Normal : In case of infection , 4000-10000 cells / mm^3 02. DLC ( DIFFERENTIAL LEUKOCYTE COUNT ) Normal NEUTROPHIL : 80%; In case of infection : less than 80%

21. b. BACTERIOLOGY INVESTIGATION : SPECIMENS : PUS – From wound or absence or burns . NASAL SWAB – From suspected carrier . FOOD – To diagnose staphylococcal intoxication . BLOOD – To diagnose endocarditis and bacteremia . SPUTUM – To diagnose lower respiratory track infection . CULTURE AND ISOLATION : Specimen are cultured on BA plate and are incubated at 37c for 24 hours . After incubation BA plate is observed for significant bacterial growth ( less than 2mm in diameter ) .

22. Then gram staining is performed of the isolation organism . Then subculture on NA plate for future biochemical test . TUBE COAGULASE TEST : 01. Mix 0.5 ml of human plasma with 0.1 ml of an overnight broth culture of staphylococcus aureus . 02. Incubate the mix in a water bath at 37c for 3-6 hours . RESULT : Plasma clots and don’t flow if the tube is inverted .

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