antibiotic actionW13s

G penicillins have high therapeutic index host does

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Unformatted text preview: er therapeutic index means “better” drug (all other things being equal) •  drugs that affect peptidoglycan (e.g., penicillins) have high therapeutic index; host does not possess peptidoglycan •  drugs that affect protein synthesis, cell membrane function may have lower therapeutic index side effects: undesirable effects on host •  many kinds, may involve almost any organ system •  e.g., diarrhea, kidney damage, anemia, teeth discolouration, allergic response, hypotension antib3 dilution susceptibility testing: minimal inhibitory concentration (MIC): lowest concentration of a drug that prevents growth of a particular pathogen minimal lethal concentration (MLC): lowest drug concentration that kills the pathogen -pathogen is inhibited -are the cells dead or just inhibited? -bacteria-static at this concentration? - (Fig 27.10, 12th ed) •  “static” •  MIC plate •  “cidal” •  MLC double or 4X "static" concentration antib4 agar diffusion (or Kirby-Bauer or disk diffusion) technique to assay antibiotic sensitivity the Etest ( http://www.biomerieux-diagnostics.com/servlet/srt/bio/clinicaldiagnostics/dynPage?doc=CNL_CLN_PRD_G_PRD_CLN_22) •  very convenient for anaerobes -test multiple antibiotics on one plate -very convenient for anaerobes (Fig 27.11 Madigan et al., 12th ed; Fig 20-11, 11th ed) antib5 (for reference only) antib5a (for reference only) mode of action of major antimicrobial chemotherapeutic agents: THF: tetrahydrofolate; DHF: dihydrofolate (Fig 27.12, Madigan et al, 12th ed; Fig 20.14, 11th ed) antib6 synthetic chemotherapeutic agents: antib7 •  growth factor analogues •  related to sulfanilamide = structural analog of p-aminobenzoic acid (PABA) •  act by blocking bacterial folic acid synthesis → results in disruption of bacterial purine (nucleic acid) synthesis •  animal host is unaffected – obtains folic acid in diet •  resistance: shown by bacteria with ability to use exogenous sources of preformed folic acid -analo...
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