Escherichia coli and Staphylococcus saprophyticus were the most common pathogens found in the urine samples, accounting for 90 percent of the infections studied. The prevalence of resistance among E coli and all pathogens combined was more than 20 percent for ampicillin, cephalothin and sulfamethoxazole in each year studied. The prevalence of resistance to trimethoprim and trimethoprim-sulfamethoxazole rose from more than 9 percent in 1992 to more than 18 percent in 1996 among E coli, and from 8 percent to 16 percent among all isolates combined. In contrast, the prevalence of resistance to nitrofurantoin, gentamicin and ciprofloxacin hydrochloride was 0 percent to 2 percent among E coli and less than 10 percent among all pathogens combined, and did not change significantly during the five-year period. Of considerably greater concern is the increasing prevalence of resistance to trimethoprim and trimethoprim-sulfamethoxazole that we observed.
Bacterial strains tend to develop resistance to antibiotics that are used frequently.
Thus, rates of resistance of bacteria to a particular antibiotic vary from community to community, depending on which antibiotics are commonly prescribed. The authors state that, in their view, when the prevalence of resistance to trimethoprim or trimethoprim-sulfamethoxazole among cystitis bacterial isolates exceeds 15 percent to 20 percent in a community, those antibiotic should not be used routinely to treat acute cystitis. They conclude by writing that when physicians are choosing a therapy for patients with this type of urinary tract infection, antibiotic resistance must be considered in addition to other factors such as efficacy, adverse effects, cost and cost-effectiveness. The continued evolution of antimicrobial resistance among community-acquired isolates is worrisome and mandates both further surveillance and new approaches to slow the emergence of resistance. Inc. Go back to the top.