3. Specimens Collected
Depends on type of lesion / disease
Pus (aspirates or swabs)
Sputum (in respiratory infections)
Blood (in endocarditis,
septicaemia)
Pleural fluid (in empyema)
Nasal swab (detection of MRSA
carriage) Deepa Babin at TMC Kollam 3
4. Direct Microscopy
Pus cells
Gram stain of pus
Pus cells with Gram
positive cocci (GPC) in
groups
GPC in groups
Deepa Babin at TMC Kollam 4
5. Culturing of Staphylococcus
Media used:
Blood agar, chocolate agar, MacConkey agar
Mannitol salt agar (Selective / Differential medium)
Liquid media: Glucose broth, brain-heart infusion broth
Colony characteristics
On blood agar: Golden yellow, opaque, β-lytic
colonies
On mannitol salt agar: yellow colonies (mannitol
fermenting)
Deepa Babin at TMC Kollam 5
6. Identification of Isolate
Gram smear examination
Positive catalase test (to distinguish from Tube Coagulase Test
streptococci)
Positive coagulase test (to distinguish
Staphylococcus aureus from other
staphylococci)
Slide coagulase test
For detection of bound coagulase
Make a saline suspension of the
+
organism on a clear glass slide; add a
drop of human plasma
Immediate clumping indicates a positive
reaction
Tube coagulase test
0.1ml of overnight broth culture of
organism is mixed with 0.5ml of citrated / –
oxalated / heparinised human plasma in a
test tube
Tube is incubated at 37ºC for 3–6 hours
in a water bath
A plasma clot indicates the presence of
free coagulase
Positive DNase test (to distinguish
Staphylococcus aureus from other
staphylococci)
Deepa Babin at TMC Kollam 6
7. Antibiotic Sensitivity Testing
I line II line
Penicillin (Ampicillin in
urinary isolates) Vancomycin
Gentamicin
Erythromycin (not used in Rifampicin
urinary isolates)
Clindamycin
Cephalothin (I generation
cephalosporin) Linezolid
Amoxicillin-Clavulanate
Oxacillin (or Netilmicin
Cloxacillin,cefoxitin)
Amikacin
Tetracycline
Nitrofurantoin (only in
urinary isolates)
Deepa Babin at TMC Kollam 7
8. Treatment
If Penicillin is sensitive:
Penicillin is the drug of choice
If not sensitive
Oxacillin / Cloxacillin + an Aminiglycoside
For MRSA
Vancomycin or Linezolid
Chlorhexidine or Mupirocin for local application
Treatment of abscesses
Drainage is essential + antibiotics
In severe, life-threatening infections
(septicaemia, endocarditis,
pneumonia,osteomylitis)
Oxacillin / Cloxacillin + an aminiglycoside
Deepa Babin at TMC Kollam 8
9. Coagulase Negative
Staphylococci
Staphylococcus epidermidis
Stitch abscess
Infection associated with artificial implants and
prosthetics, such as:
Central venous line
Intra ocular lens
Ventriculo-peritoneal shunt
Artificial heart valves (endocarditis)
Artificial joints
Staphylococcus saprophyticus
Causes UTI in young adult females
Resistant to Novobiocin (as opposed to
Staphylococcus epidermidis, which is sensitive)
Deepa Babin at TMC Kollam 9