Antiseptic – kills and inhibits organisms on body

  Disinfectant – kills and inhibits organisms on inanimate objects

  Sterilization – all organisms killed

  Common antiseptics in surgery

•  Iodophors (Betadine) – good for GPCs and GNRs; poor for fungi

•  Chlorhexidine gluconate (Hibiclens) – good for GPCs, GNRs, and fungi

MECHANISM OF ACTION

  Inhibitors of cell wall synthesis – penicillins, cephalosporins, carbapenems, monobactams, vancomycin

  Inhibitors of the 30s ribosome and protein synthesis – tetracycline, aminoglycosides (tobramycin, gentamicin), linezolid

  Inhibitors of the 50s ribosome and protein synthesis – erythromycin, clindamycin, Synercid

  Inhibitor of DNA helicase (DNA gyrase) – quinolones

  Inhibitor of RNA polymerase – rifampin

  Produces oxygen radicals that breakup DNA – metronidazole (Flagyl)

  Sulfonamides – PABA analogue, inhibits purine synthesis

  Trimethoprim – inhibits dihydrofolate reductase, which inhibits purine synthesis

  Bacteriostatic antibiotics – tetracycline, clindamycin, erythromycin (all have reversible ribosomal binding), Bactrim

  Aminoglycosides – have irreversible binding to ribosome and are considered bactericidal

MECHANISM OF ANTIBIOTIC RESISTANCE

  PCN resistance – due to plasmids for beta-lactamase

  Transfer of plasmids – most common method of antibiotic resistance

  Methicillin-resistant S. aureus (MRSA) – resistance caused by a mutation of cell wall–binding protein

  Vancomycin-resistant Enterococcus (VRE) – resistance caused by a mutation in cell wall–binding protein

  Gentamicin resistance – resistance due to modifying enzymes leading to a decrease in active transport of gentamicin into the bacteria

APPROPRIATE DRUG LEVELS

  Vancomycin – peak 20–40 µg/mL; trough 5–10 µg/mL

  Gentamicin – peak 6–10 µg/mL; trough < 1 µg/mL

  Peak too high → decrease amount of each dose

  Trough too high → decrease frequency of doses (increase time interval between doses)

SPECIFIC ANTIBIOTICS

  Penicillin

•  GPCs – streptococci, syphilis, Neisseria meningitides (GPR), Clostridium perfringens (GPR), beta-hemolytic Streptococcus, anthrax

•  Not effective against Staphylococcus or Enterococcus

  Oxacillin and nafcillin

•  Anti-staph penicillins (staph only)

  Ampicillin and amoxicillin

•  Same as penicillin but also picks up enterococci

  Unasyn

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