STAPHYLOCOCCUS

Gram positive cocci arranged in grape like clusters

Commonest cause of localized suppurative lesions in humans

Habitat includes skin ,hair,anterior nasal area Imp sps- S.aureus,

S.epidermidis,S.saprophyticus etc

Staphylococcus aureus

MORPHOLOGY Gram poitive ,Arranged in grape like

clusters,Non motile, Non sporing, Non capsulated

1 micrometer in diameter

STAPHYLOCOCCUS

CULTURAL CHARACTERS

Grow readly on ordinary media Temp range-10-42 degree Celsius,

Optimum-37 Ph-7.4-7.6 They are aerobes and facultative anaerobes Common media are Nutrient agar & Blood

agar

On Nutrient agar

2-4 mm diameter colony.circular ,smooth ,convex ,Most strains produce golden yellow pigment

Colonies of staphylococcus aureus

On Blood agar

Produce beta hemolytic colonies

Colonies of staphylococcus albus

Colonies of staphylococcus cetreus

Colonies on biood agar

Selective media is Mannitol salt agar Produce yellow colonies on mannitol salt

agar

Selective media-mannitol salt agar

Biochemical propertis

Catalase + Oxidase – Coagulase +

Following properties are imp to distigush S.aureus from other non pathogenic sps

Coagulase production Mannilol fermentation Golden yellow pigment Liquefy gelatin Phosphatase production DNase production

ANTIGENIC STRUCTURE & VIRULANCE FACTORS

ANTIGENIC STRUCTURECapsule Some strains have a capsule. That inhibit phagocytosis, they

inhibit opsonisation Capsulated strains are more virulentPeptidoglycan Give rigidity to the cell wall, activtes complimentTeichoic acid Major antigenic component Protect cell from compliment mediated opsonisationProtein A It has chemotactic,antiphagocytic & anti complimentary action

TOXINS & ENZYMES

Staph aureus produce a number of toxins & extra cellular enzymes

TOXINS

1. Cytolytic toxin

2. Entero toxin

3. Toxic shock syndrome toxin

4. Exfoliative(epidrmolytic toxin)

CYTOLYTIC TOXIN

2 Types HEMOLYSIN & LEUCOCIDINS

HEMOLYSIN Lyse RBCs 4 types ie, alpha, beta ,gamma & delta

LEUCOCIDINS Damage polymorphonuclear lecocytes

ENTERO TOXIN

Responsible for staphylococcal food poisoning

Nosiea,vomitting & diarrhea in 2-6 hrs after consumption of contaminated food

Meat ,fish ,milk & milks products are the main foods responsible for this condition

Source of infection is a food handler who is a carrier.

TOXIC SHOCK SYNDROME TOXIN

Causing toxic shock syndrome It is a fatal multi system disease with

fever ,hypotension,myalgia,vomitting, diarrhea, erythematous rashes etc

It is potentially a a fatal diasease

Exfoliative (epidermolytic) toxin

Responsible for staphylococcal scaled skin disease

Here the outer layer of epidermis gets separated from the underlying tissue

ENZYMES

COAGULASE It is the most important enzyme which brings the clotting of

human or rabbit plasma 2 types of coagulase engyme- Bound coagulase-which is bound to the cell wall Free coagulase-which is liberated free in to the surrounding

medium This enzyme can be demonstrated by COAGULASE TEST Coagulase test is the standard criteria for the identification of

Staph aureus SLIDE Test (For bound coagulase) & TUBE Test(for free

coagulase) are there

Other enzymes Lipases Hyaluronidase Nuclease

STAPHYLOCOCCAL DISEASES

Skin & soft tissue infections Folliculitis Furancles(boils) Wound infections Brest abscess Carbuncles Cellulitis Styes

CARBUNCLES

Multiple carbuncles

Abscess

Wound infection

cellulitis

faurancles

boils

styes

Brest abscess

impetigo

MUSCULOSKELETAL INFECTIONS

Osteomyelitis Arthritis etc

osteomyaliytis

RESPIRATORY INFECTIONS

Tonsillitis Pharyngitis Sinusitis Otis Broncho npneumonia Lung abscess Empyemia

Lung abscess

tonsillitis

CNS INFECTIONS

Brain abscess Meningitis etc

meningitis

Endo vascular infections

Bacteremia Septicemia Pyemia Endocarditis

URINARY INFECTIONS Staph are uncommon in UTI, but may cause

infections in association with lacal instrumentation, implants or diabetes

TOXIN ASSOCIATED DISEASES

Food poisoning

Toxic shock syndrome

Scaled skin disease

Staphylococcal infections

LAB DIAGNOSIS

SPECIMENSSpecimens are to be depend on the type of lesions1. Pus(suppurative lesions)2. Sputum(respiratory infections)3. Blood(endo vascular)4. CSF(CNS infections)5. Urine (UTI)6. Feces,vomit,remains of suspected food(food

poisoning)7. Nasal swab(carriers)

METHODS

Direct microscopy

Smears of material shows gram positive cocci in clusters

Culture

Inoculated on to BLOOD AGAR ,NUTRIENT AGAR etc

Look for typical colony morphology,hemolysis,pigmentation etc

BICHEMICHAL REACTIONS

Catalase - positive Oxidase - negative Coagulase -positive DNase -positive Phosphatase - positive Mannitiol fermentation -positve

COAGULASE TEST

It is the main lab test used to differenciate staph aureus from other sps of

2 types –slide test & tube test

Slide coagulase test

Few colonies are emulsified in a drop of normal saline on a slide and mixed with a drop of rabbit or human plasma.

Clumping indicates positive reaction

Slide coagulase test

TUBE COAGULASE test

Done to detect free coagulase 0.1 ml broth culture of the isolate is added to

0.5 ml of human or rabbit plasma in a narrow test tube.

The tubes incubated at 37 degree Celsius for 3-6 hrs

If positive ,the plasma clots & does not flow when the tube is tilted

Tube coagulase test

Mannitol fermentation

tretment

Benzyl penicillin is most effective Methicillin ,cloxacillin etc can be used in

penicillinase producing strainsMRSA(Methicillin resistant staph aureus)They are causing grate problem to cliniciansThey are resistant to penicillins & other beta lactam

antibioticsThey can be treated by vancomycin &teicoplaninTreatment of carriers by local application of

antibiotics like as bacitracin