Resistant pathogens in urinary tract infections.

Antimicrobial susceptibility of bacteria causing urinary tract infection (UTI) has evolved over several decades as antimicrobial exposure has repeatedly been followed by emergence of resistance. Older populations in the community, long-term care facilities, or acute care facilities have an increased prevalence of resistant bacteria isolated from UTI. Resistant isolates are more frequent in long-term care populations than the community. Resistant isolates include common uropathogens, such as Escherichia coli or Proteus mirabilis, and organisms with higher levels of intrinsic resistance, such as Pseudomonas aeruginosa or Providencia stuartii. Isolation of resistant organisms is consistently associated with prior antimicrobial exposure and higher functional impairment. The increased likelihood of resistant bacteria makes it essential that a urine specimen for culture and susceptibility testing be obtained before instituting antimicrobial therapy. Therapy for the individual patient must be balanced with the possibility that antimicrobial use will promote further resistance. Antimicrobial therapy should be avoided unless there is a clear clinical indication. In particular, asymptomatic bacteriuria should not be treated with antimicrobials. Where symptoms are mild or equivocal, urine culture results should be obtained before initiating therapy. This permits selection of specific therapy for the infecting organism and avoids empiric, usually broad-spectrum, therapy. Where empirical therapy is necessary, prior infecting organisms should be isolated, and recent antimicrobial therapy, as well as regional or facility susceptibility patterns, should be considered in antimicrobial choice. Where empirical therapy is used, it should be reassessed 48 to 72 hours after initiation, once pretherapy cultures are available.