Antimicrobial resistance in community and nosocomial Escherichia coli urinary tract isolates from Chennai, South India in 2007

Escherichia coli are the commonest cause of community and nosocomial urinary tract infection (UTI). Antibiotic treatment is usually empirical relying on susceptibility data from local surveillance studies. We therefore set out to determine levels of resistance to 9 commonly used antimicrobial agents amongst all urinary isolates obtained over a 12 month period. Methods: Antimicrobial susceptibility to ampicillin, amoxicillin/clavulanate, cephalexin, cefpodoxime, norfloxacin, amikacin, nitrofurantoin, trimethoprim and imipenem was determined for 14,678 E. coli urinary isolates obtained from community and hospitalised patients in Chennai, South India. Results: Imipenem was the most active agent (100% susceptible), followed by nitrofurantoin and amikacin (94% each). High rates of resistance to ampicillin (82%) and co-trimoxazole (76%), often in combination with norfloxacin were observed in both sets of isolates. Although 65% of the isolates exhibited resistance to multiple drug classes, resistance to cefpodoxime, indicative of extended spectrum β-lactamase production, was observed in 40% of community and 60% of nosocomial isolates. Conclusion: With the exception of nitrofurantoin, resistance to agents commonly used as empirical oral treatments for UTI was extremely high. Levels of resistance to trimethoprim and ampicillin render them unsuitable for empirical use. Continued surveillance and investigation of other oral agents for treatment of UTI in the community is required