Modes of action - Antibiotic Sensitivity Test -- Disk-plate...

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1/01 Modes of action 1. Interfere with microbe’s vital metabolic process that does not occur in host cells (inhibit microbial enzymes) Act by: a. Competitive inhibition – competes with essential substrate to act with microbial enzyme b. Noncompetitive inhibition – reacts directly with enzyme 2. Targets structural/ metabolic differences between eukaryotic, prokaryotic cells. 3. Action of antimicrobial agents - interfere with: a. Metabolic pathways – production of an essential metabolite (by competitive inhibition) b. The cell wall (murein) synthesis c. Protein synthesis (enzymes) d. Nucleic acid replication/transcription e. Cause damage to cell membrane
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Unformatted text preview: Antibiotic Sensitivity Test -- Disk-plate (diffusion) method 1. Procedure a. Isolate and identify causative pathogen b. Grow pathogen in pure culture c. Seed surface agar plate - inoculate entire surface with pure culture d. Place paper antibiotic disks on surface of agar e. Incubate 24 hours, observe growth around disks 2. Principle: during incubation antibiotic diffuses into agar, if effective, inhibits growth 3. Observations: a. Zone of inhibition (no growth) - effective (positive) b. No zone of inhibition (growth) - not effective (negative) c. Resistant strains - isolated colonies in zone of inhibition 1...
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