Staphylococcus aureus
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Staphylococci are Gram positive cocci that commonly cause localized suppurative lesions. Staphylococcus aureus is an important pathogenic species that can cause a variety of infections like food poisoning, toxic shock syndrome, and nosocomial infections. S. aureus has developed resistance to many antibiotics like penicillin through production of beta-lactamases. Methicillin resistant S. aureus strains are a major concern as they are resistant even to methicillin and related antibiotics.
Staphylococcus aureus
- 2. Staphylococci are Gram positive cocci arranged in grapeStaphylococci are Gram positive cocci arranged in grape like clusters.like clusters. Ubiquitous and commonest cause of localizedUbiquitous and commonest cause of localized suppurative lesion.suppurative lesion. Has the tendency of developing resistance to penicillinsHas the tendency of developing resistance to penicillins and other antibiotics very easily.and other antibiotics very easily. Medically important speciesMedically important species areare Staphylococcus aureusStaphylococcus aureus Staphylococcus epidermidisStaphylococcus epidermidis Staphylococcus saprophyticus.Staphylococcus saprophyticus. INTRODUCTION
- 3. STAPHYLOCOCCUSSTAPHYLOCOCCUS AUREUSAUREUS Morphology:Morphology: Gram positive cocci arranged inGram positive cocci arranged in grape like clusters.grape like clusters. Non motile.Non motile. Non sporing.Non sporing. Approx.Approx.11µm in diameter.µm in diameter.
- 4. STAPHYLOCOCCUSSTAPHYLOCOCCUS AUREUSAUREUS Culture characteristics:Culture characteristics: Grow readily on ordinary culture media.Grow readily on ordinary culture media. Optimum temp-37°COptimum temp-37°C Optimum pH-7.4-7.6Optimum pH-7.4-7.6 Aerobes & facultative anaerobes.Aerobes & facultative anaerobes.
- 5. CULTURALCULTURAL CHARACTERISTICS:CHARACTERISTICS: NUTRIENT AGARNUTRIENT AGAR Colonies are 2-4 mm dia,Colonies are 2-4 mm dia, Circular, smooth, convex,Circular, smooth, convex, opaque ,easily emulsifiable.opaque ,easily emulsifiable. Most of the strains produceMost of the strains produce golden yellow pigment.golden yellow pigment. On slope -‘Oil paint’On slope -‘Oil paint’ appearanceappearance
- 6. CULTURALCULTURAL CHARACTERISTICSCHARACTERISTICS On Blood agarOn Blood agar - β hemolytic colonies.- β hemolytic colonies. On Mac ConkeyOn Mac Conkey - Lactose fermenting pink colonies.- Lactose fermenting pink colonies. Selective media:Selective media: Contain 8-10% NaCl, lithium chloride, tellurite &Contain 8-10% NaCl, lithium chloride, tellurite & Polymyxin.Polymyxin. Mannitol salt agar:Mannitol salt agar: Yellow colonies -Mannitol fermentation.Yellow colonies -Mannitol fermentation. Liquid mediumLiquid medium: Uniform turbidity.: Uniform turbidity.
- 8. BIOCHEMICALBIOCHEMICAL REACTIONSREACTIONS Catalase positiveCatalase positive Coagulase positiveCoagulase positive Oxidase negativeOxidase negative Hydrolyses ureaHydrolyses urea Reduces nitrate to nitritesReduces nitrate to nitrites Tellurite reductionTellurite reduction Liquefy gelatinLiquefy gelatin MR and VP positiveMR and VP positive coagulase catalase
- 9. BIOCHEMICALBIOCHEMICAL REACTIONSREACTIONS Indole negativeIndole negative Produce phosphataseProduce phosphatase Ferments number of sugars, producing acid andFerments number of sugars, producing acid and no gasno gas Fermentation of mannitolFermentation of mannitol is importantis important Most strains are lipolytic and hence producesMost strains are lipolytic and hence produces dense opacity when grown on media containingdense opacity when grown on media containing egg yolkegg yolk
- 10. β hemolysis on blood agar.β hemolysis on blood agar. Production of golden yellow pigment.Production of golden yellow pigment. Coagulase production.Coagulase production. Mannitol fermentation.Mannitol fermentation. Gelatin liquefaction.Gelatin liquefaction. Phosphatse production.Phosphatse production. Production of enzyme deoxyribonuclease.Production of enzyme deoxyribonuclease. Tellurite reduction.Tellurite reduction. Pathogenic strain & Non pathogenicPathogenic strain & Non pathogenic strain-Differencesstrain-Differences
- 11. Antigenic structure:Antigenic structure: CapsuleCapsule PeptidoglycanPeptidoglycan TeichoicTeichoic acidacid Protein AProtein A Toxins:Toxins: Haemolytic toxinsHaemolytic toxins :: α, β, γ, δ.α, β, γ, δ. Leucocidin,Leucocidin, Epidermolytic toxins,Epidermolytic toxins, EnterotoxinsEnterotoxins Toxic shock syndrome toxinToxic shock syndrome toxin
- 12. Extracellular enzymesExtracellular enzymes Coagulase:Coagulase: 8 antigenic types : A-H, mostly A.8 antigenic types : A-H, mostly A. Has property to clot human or rabbit plasma.Has property to clot human or rabbit plasma. Activates Coagulase Reacting Factor (CRF) present in theActivates Coagulase Reacting Factor (CRF) present in the plasma, converts fibrinogen to fibrin and clots the plasma.plasma, converts fibrinogen to fibrin and clots the plasma. May coat the organism and prevents opsonisation andMay coat the organism and prevents opsonisation and phagocytosis.phagocytosis. Free coagulase- tube coagulase test.Free coagulase- tube coagulase test. Bound coagulase- slide coagulase test.Bound coagulase- slide coagulase test.
- 13. PathogenicityPathogenicity About 30-50% of adults carry S.aureus inAbout 30-50% of adults carry S.aureus in anterior nares and perineum, axillae, vaginaanterior nares and perineum, axillae, vagina Mode of transmission is by contact, fomites orMode of transmission is by contact, fomites or by dropletsby droplets Enters the body through damaged skin,mucousEnters the body through damaged skin,mucous membranes and following viral infections (esp.membranes and following viral infections (esp. LRTI).LRTI). Diseases of Staph. aureus are divided intoDiseases of Staph. aureus are divided into TOXIN MEDIATED and due toTOXIN MEDIATED and due to INVASION.INVASION.
- 14. PathogenicityPathogenicity 1.Cutaneous infections.1.Cutaneous infections. Pustules, boils, carbuncles, abscesses, styes,Pustules, boils, carbuncles, abscesses, styes, impetigo, wound & burn infection.impetigo, wound & burn infection. 2. Deep infections:2. Deep infections: Osteomyelitis, tonsilitis, pharyngitis, sinusitis,Osteomyelitis, tonsilitis, pharyngitis, sinusitis, endocarditis, meningitis, bacteriaemia,endocarditis, meningitis, bacteriaemia, septicaemia.septicaemia.
- 15. 3.Food poisoning3.Food poisoning Heat stable toxin-100Heat stable toxin-100ºC for 10 to 40 min.ºC for 10 to 40 min. Nausea, vomiting and diarrhoea occurs 2 to 6Nausea, vomiting and diarrhoea occurs 2 to 6 hours after consuming preformed toxin.hours after consuming preformed toxin. Cooked meat, fish, milk and milk products areCooked meat, fish, milk and milk products are mostly responsible.mostly responsible. Self limitingSelf limiting Neutralized by specific antitoxin.Neutralized by specific antitoxin. Detection by latex agglutination and ELISADetection by latex agglutination and ELISA
- 16. 4.Exfoliative diseases4.Exfoliative diseases Epidermolytic toxinEpidermolytic toxin Stripping superficial layers ofStripping superficial layers of epidermis from underlyingepidermis from underlying tissue-blister formationtissue-blister formation Most dramatic disease isMost dramatic disease is Scalded Skin Syndrome orScalded Skin Syndrome or Ritter’s disease mostly seen inRitter’s disease mostly seen in newborns and previouslynewborns and previously healthy childrenhealthy children
- 17. 5. Toxic Shock Syndrome5. Toxic Shock Syndrome Potentially multisystem disorder with fever,Potentially multisystem disorder with fever, hypotension, myalgia, rash, vomiting, diarrhoeahypotension, myalgia, rash, vomiting, diarrhoea etc.,etc., First seen in children and adolescent in 1978 butFirst seen in children and adolescent in 1978 but widely known after an outbreak occurred inwidely known after an outbreak occurred in menstruating women using absorbent vaginalmenstruating women using absorbent vaginal tampons which was heavily colonised by Staph.tampons which was heavily colonised by Staph. aureus in USA in 1980.aureus in USA in 1980. 6. Important cause of nosocomial infection6. Important cause of nosocomial infection
- 18. S. aureus and Disease Ostermylelitis Food Poisoning Scalded Skin Syndrome Toxic Shock Syndrome Impetigo Boils PneumoniaEndophthalmitis Endocarditis Cellulitis
- 19. LABORATORY DIAGNOSISLABORATORY DIAGNOSIS 1.1. Specimen:Specimen: • Pus- Suppurative lesionsPus- Suppurative lesions • Sputum- Respiratory infectionsSputum- Respiratory infections • Blood- Seticaemia or PUOBlood- Seticaemia or PUO • Urine- Urinary tract infectionUrine- Urinary tract infection • CSF- MeningitisCSF- Meningitis • Faeces - Food poisoningFaeces - Food poisoning • Food/Vomit-Food poisoningFood/Vomit-Food poisoning
- 20. LABORATORY DIAGNOSISLABORATORY DIAGNOSIS 2.2. Collection & transport-Collection & transport- Specimen to be collected in a sterile containerSpecimen to be collected in a sterile container under all aseptic conditions transportedunder all aseptic conditions transported immediately to the lab.immediately to the lab. 3.3. Direct microscopy :Direct microscopy : Gram stain- shows Gram positive cocci inGram stain- shows Gram positive cocci in clusters.clusters. 4.4. Culture :Culture : Blood agar, Peptone water, selective mediaBlood agar, Peptone water, selective media in necessary like mannitol salt agar etc., to bein necessary like mannitol salt agar etc., to be incubated at 37incubated at 37°C for 24 hours.°C for 24 hours.
- 21. LABORATORY DIAGNOSISLABORATORY DIAGNOSIS 5.5. Colony morphology & gram staining.Colony morphology & gram staining. 6.6. Biochemical reactionsBiochemical reactions 7.7. Antibiotic sensitivity testing-Antibiotic sensitivity testing- Kirby BauerKirby Bauer method.method. 88. Phage typing, DNA typing. Phage typing, DNA typing forfor epidemiological studiesepidemiological studies
- 22. DRUG RESISTANCEDRUG RESISTANCE Most of the strains of S.aureus were resistantMost of the strains of S.aureus were resistant to penicillin originally, soon resistant strainsto penicillin originally, soon resistant strains began to emerge. Due tobegan to emerge. Due to I)I) Production of beta lactamasesProduction of beta lactamases ( plasmid mediated).( plasmid mediated). ββ lactamase inactivates penicillin bylactamase inactivates penicillin by splitting thesplitting the ββ lactam ringlactam ring
- 23. DRUG RESISTANCEDRUG RESISTANCE II) Reduction in affinity of of penicillin bindingII) Reduction in affinity of of penicillin binding protein of Saphylococcal cell wall forprotein of Saphylococcal cell wall for ββ lactamlactam antibiotics.antibiotics. It is chromosomally mediated and evenIt is chromosomally mediated and even involvesinvolves ββ lactamase resistant penicillin such aslactamase resistant penicillin such as Methicillin, nafcillin & oxacillin.These starinsMethicillin, nafcillin & oxacillin.These starins are called Methicillin Resistant Staph. Aureusare called Methicillin Resistant Staph. Aureus (MRSA).(MRSA). • Vancomycin/Teicoplanin is used for treatmentVancomycin/Teicoplanin is used for treatment following infections with MRSAfollowing infections with MRSA
- 24. TreatmentTreatment Benzyl penicillinBenzyl penicillin CloxacillinsCloxacillins VancomycinVancomycin TeicoplaninTeicoplanin Superficial inections-Superficial inections- Bacitracin / ChlorhexidineBacitracin / Chlorhexidine