MRSA , pathogenesis lab diagnosis and treatment

1. CULTURE
SEMINAR
(MRSA)
ARPITA CHANDRA
Medical Microbiology

2. Catalase positive
Coagulase positive
Facultative anaerobe
Non- motile
Non sporing
Gram positive cocci
Purple colour cocci - Gram stain
Produces golden yellow pigment –NA
Beta hemolytic – BA

3.  Peptidolycan
 Teichoic Acid
 Protein- A
 Toxins and Enzymes
Toxins
1. Haemolysins -Alpha lysin
Beta lysin
Gamma lysin
Delta lysin
2. Leucocidin
 Toxic shock syndrome toxin
 Exfoliative toxin
2. ENZYMES
Coagulase enzyme

4. Mechanism -1
MecA gene (staph aureus)
Responsible for Methicillin drug resistance
Mechanism-2
Penicilinase producing S. aureus
Altered PBP( penicillin binding protein) to PBP-2
Methicillin resistance

5.  ON NUTRIENT AGAR- yellow pigment looks like oil paint
 ON BLOOD AGAR- beta hemolysis
 MAC-CONKEY AGAR- pink colour (lactose fermenting)
 LIQUID MEDIUM- peptone water (uniform turbidity)
 SELECTIVE MEDIA
 Mannitol salt agar
 Salt milk agar

6.  Using Cefoxitin (20µg)disc diffusion (According to CLSI guideline)
 < 21mm zone size = MRSA
 Cefoxitin e- strip
 PCR -MecA gene detection
 MIC TEST

7.  Methicillin- poor activity during storage
- Not available in market
Oxacillin- Required 2-4% NaCl
Temperature- 30°C
Incubation Period -24hr
Advantages of Cefoxitin drug-
MecA gene inducer
Temperature- 37°C
Incubation period- 16-18hrs
No requirement of salt

8.  Vancomycin (after E-testing)
 Quinupristin/dalfopristin
 Teicoplanine
 Linozolid

9. Thank you