Selecting an appropriate antimicrobial drug
to treat a specific in-fection involves several important factors:
§ First, the microorganism must be isolated and
identified—gen-erally through growing a culture.
§ Then its susceptibility to various drugs must
be determined. Be-cause culture and sensitivity results take 48 hours,
treatment usu-ally starts at assessment and then is reevaluated when test
results are obtained.
§ The location of the infection must be
considered. For therapy to be effective, an adequate concentration of the
antimicrobial must be delivered to the infection site.
§ Lastly, the cost of the drug must be
considered as well as its po-tential adverse effects and the possibility of
The usefulness of antimicrobial drugs is limited by pathogens that may
develop resistance to a drug’s action.
Resistance is the
ability of a microorganism to live and grow in the presence of an antimicrobial
drug that’s either bacteriostatic (inhibits the growth or multiplication of
bacteria) or bactericidal
§ (kills bacteria). Resistance usually results from genetic mutation of
the microorganism. (See The rise of the resistance movement.)