Page 129 - MNU-PM502- Pharmaeutical Microbiology Theoritical Book

Pharm D- Clinical Pharmacy Program Third Level Pharmaceutical Microbiology& Antimicrobials (PM 502)

I. Production of Drug-inactivating Enzymes
❑ -lactamases: convert penicillins and cephalosporins into penicilloic and
cephalosporic acids.
.

❑ Enzymes that cause chemical alteration

II- Change in target site

Modifications of the target site that result in decreased
affinity for the antibiotic molecule

- Methicillin resistance in S. aureus (MRSA) due to the

acquisition of mecA gene encodes PBP2a, that has low
affinity for all β-lactams
- Vancomycin resistance:

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