Microbiology Chapter 12

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  1. Antibiotic
    Chemical substances, produced by living organisms that inhibit the growth of other organisms
  2. Microbiocidal
    Kills organism
  3. Microbiostatic
    Slows growth of organism (but not dead)
  4. 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)
  5. 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)
  6. 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
  7. Anti-Metabolites
    Medications used for UTIs. Deprive bacteria of nutrients by transferring with metabolic pathways. (Common: sulfonamides, INH, Trimethoprim)
  8. Nucleic acid agents
    • interferes with DNA replication. 
    • Common: Quinolones, difloxacin, amifloxicin, ciprofloxacin
  9. 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.
  10. MRSA
    Methicillin Resistant Staphylococcus aureus
  11. VRE
    Vancomycin Resistant Enterococcus
  12. Susceptible (sensitive)
    Organism inhibited/killed by antibiotic 
  13. Resistant
    Organism is not inhibited/killed by antibiotic 
  14. Alexander Fleming
    1928: discovers penicillin
  15. Howard Foley
    1940: isolates pure penicillin
  16. Bacterial resistance
    Bacterial growth unaffected by antibiotic
  17. Bacterial susceptibility
    Bacterial growth is inhibited by antibiotic
  18. Susceptibility testing
    Lab techniques to determine the effectiveness of specific antibiotics against a specific bacteria
  19. Mean Inhibitory Concentration (MIC)
    Lowest concentration of antibiotic that inhibits bacterial growth 
  20. Minimum Bacteriocidal Concentration (MBC)
    Lowest concentration of antibiotic that kills bacteria
  21. Antibiotic classifications
    • Cell wall agents
    • Cell membrane agents
    • Anti-protein agents
    • Anti-metabolite agents
    • Nucleic acid agents
  22. Penicillin (Penicillin G)
    • Beta-lactam antibiotic
    • Inhibits cell wall peptidoglycan cross-linkages
    • Effective only against actively dividing bacteria
  23. Semi - Synthetic Penicillins
    Chemical modification of the original penicillin molecule
  24. Vancomycin
    • Anti - cell wall agent 
    • Interferes with peptidoglycan matrix
    • Effective against gram positive bacteria only
    • Last resort for MRSA
Card Set:
Microbiology Chapter 12
2013-02-15 16:11:08
Clinical Microbiology

Antibiotic Mechanisms of Action and Resistance
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