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Antibiotic
Chemical substances, produced by living organisms that inhibit the growth of other organisms
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Microbiocidal
Kills organism
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Microbiostatic
Slows growth of organism (but not dead)
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Cell wall agents
Common, generally effective and non-toxic for humans, but toxic for bacteria. Beta-lactam antibiotics are common cell wall agents (penicillin, cephalosporins, monobactams, carbapenems)
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Cell membrane agents
bacteria and humans have cell membranes. Antibiotics tend to be toxic if not used properly, commonly used as topical antibiotics. (polymyxins, bactracin, nystatin)
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Antiprotein synthesis agents
inhibits DNA -->mRNA transcription (protein synthesis). Protein synthesis occurs within the cell's ribosome. Bacteria have 30S, 50S, 70S. Humans have 40S, 60S, 80S
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Anti-Metabolites
Medications used for UTIs. Deprive bacteria of nutrients by transferring with metabolic pathways. (Common: sulfonamides, INH, Trimethoprim)
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Nucleic acid agents
- interferes with DNA replication.
- Common: Quinolones, difloxacin, amifloxicin, ciprofloxacin
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Beta-Lactamase
bacterial enzyme that breaks the chemical structure of antibiotics containing the beta-lactam ring. Organisms with this enzyme are resistant to the beta-lactam antibiotics.
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MRSA
Methicillin Resistant Staphylococcus aureus
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VRE
Vancomycin Resistant Enterococcus
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Susceptible (sensitive)
Organism inhibited/killed by antibiotic
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Resistant
Organism is not inhibited/killed by antibiotic
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Alexander Fleming
1928: discovers penicillin
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Howard Foley
1940: isolates pure penicillin
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Bacterial resistance
Bacterial growth unaffected by antibiotic
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Bacterial susceptibility
Bacterial growth is inhibited by antibiotic
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Susceptibility testing
Lab techniques to determine the effectiveness of specific antibiotics against a specific bacteria
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Mean Inhibitory Concentration (MIC)
Lowest concentration of antibiotic that inhibits bacterial growth
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Minimum Bacteriocidal Concentration (MBC)
Lowest concentration of antibiotic that kills bacteria
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Antibiotic classifications
- Cell wall agents
- Cell membrane agents
- Anti-protein agents
- Anti-metabolite agents
- Nucleic acid agents
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Penicillin (Penicillin G)
- Beta-lactam antibiotic
- Inhibits cell wall peptidoglycan cross-linkages
- Effective only against actively dividing bacteria
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Semi - Synthetic Penicillins
Chemical modification of the original penicillin molecule
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Vancomycin
- Anti - cell wall agent
- Interferes with peptidoglycan matrix
- Effective against gram positive bacteria only
- Last resort for MRSA
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