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Staphylococcus
1. 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
4. 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
5. On Nutrient agar
2-4mm diameter colony.circular ,smooth
,convex ,Most strains produce golden yellow
pigment
14. 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
15. ANTIGENIC STRUCTURE &
VIRULANCE FACTORS
ANTIGENIC STRUCTURE
Capsule
Some strains have a capsule. That inhibit phagocytosis, they
inhibit opsonisation
Capsulated strains are more virulent
Peptidoglycan
Give rigidity to the cell wall, activtes compliment
Teichoic acid
Major antigenic component
Protect cell from compliment mediated opsonisation
Protein A
It has chemotactic,antiphagocytic & anti complimentary action
16.
17. 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)
19. 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.
20. 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
22. 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
42. 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
48. LAB DIAGNOSIS
SPECIMENS
Specimens are to be depend on the type of lesions
1. 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)
49. 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
51. COAGULASE TEST
Itis 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
53. 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
56. tretment
Benzyl penicillin is most effective
Methicillin ,cloxacillin etc can be used in
penicillinase producing strains
MRSA(Methicillin resistant staph aureus)
They are causing grate problem to clinicians
They are resistant to penicillins & other beta lactam
antibiotics
They can be treated by vancomycin &teicoplanin
Treatment of carriers by local application of
antibiotics like as bacitracin