Nitrofurantoin retains antimicrobial activity against multidrug-resistant urinary Escherichia coli from US outpatients

Objectives

To examine the prevalence of multidrug-resistant (MDR) urinary Escherichia coli among US outpatients and to assess the antimicrobial activity of oral antibiotics commonly used to treat urinary tract infections (UTIs) against MDR isolates.

Methods

Antimicrobial susceptibility testing data from outpatient urine cultures in The Surveillance Network (TSN) Database USA were analysed. Six antimicrobial agents from six separate drug classes were included: ampicillin, cefalotin, ciprofloxacin, nitrofurantoin, trimethoprim/sulfamethoxazole and amoxicillin/clavulanate. Isolates were categorized as resistant to one, two, three, four, five and six agents and compared for the years 2001 and 2010. Phenotypes of MDR isolates were assessed to determine antimicrobial activity of recommended therapy for UTIs.

Results

Prevalence of MDR E. coli increased from 9.1% in 2001 (n = 29 198) to 17.0% in 2010 (n = 32 742) (P < 0.0001). In isolates that demonstrated resistance to three, four or five antimicrobial agents in 2010, resistance to nitrofurantoin was observed in only 2.1%, 7.5% and 24.1% of isolates, respectively. Conversely, widespread resistance was observed for trimethoprim/sulfamethoxazole (62.6%, 88.6% and 97.9% for isolates resistant to three, four and five agents, respectively) and ciprofloxacin (48.9%, 84.3% and 98.2% for isolates resistant to three, four and five agents, respectively).

Conclusions

Because of its consistent antimicrobial activity against MDR E. coli, nitrofurantoin remains a reliable first-line agent for the empirical treatment of acute uncomplicated cystitis.