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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