Antibiotic Selection for Urinary Tract Infection: New Microbiologic Considerations

Urinary tract infection (UTI) is an extremely common clinical condition, especially among women, half of whom will have at least one episode of acute cystitis at some point during adult life. An estimated one quarter of these women will have frequent, recurrent UTI. The microbiology of uncomplicated UTI is very predictable, with the vast majority of cases attributed to Escherichia coli. Recent reports from the United States and Europe have shown that resistance among uropathogens to agents that have traditionally been recommended as firstline therapy for uncomplicated UTI is on the rise. Although resistance to fluoroquinolone antibiotics among community-acquired uropathogens remains very low in the United States, fluoroquinolone resistance in community-acquired UTI isolates from other parts of the world has been increasingly described. Very low levels of resistance to nitrofurantoin among uropathogens has revived interest in this agent. The effect of in vitro resistance in uropathogens on the clinical response to treatment of acute cystitis is not well studied. The implications of emerging resistance among the causative agents of this extremely common infection for therapy of UTI are discussed.