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.

1. STAPHYLOCOCCUSSTAPHYLOCOCCUS

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.

7. MSA
Blood Agar
Liquid medium

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