Antimicrobial susceptibility of inpatient urinary tract isolates of gram-negative bacilli in the United States: Results from the study for monitoring antimicrobial resistance trends (SMART) program: 2009-2011

Background

The Study for Monitoring Antimicrobial Resistance Trends is an ongoing global surveillance program that has monitored the susceptibilities of Gram-negative bacilli from inpatient urinary tract infections (UTIs) since late 2009.

Objective

This analysis reports on the in vitro susceptibility of 2,135 isolates collected by 24 US sites from hospitalized patients with UTIs between 2009 and 2011.

Methods

Minimum inhibitory concentrations and susceptibility were determined according to the guidelines of the Clinical and Laboratory Standards Institute.

Results

Of the isolates collected, 88.6% (1,892) were Enterobacteriaceae, which included 48.9% (n = 1,045) Escherichia coli, 14.5% (n = 310) Klebsiella pneumoniae, 6.4% (n = 136) Proteus mirabilis, 2.5% (n = 54) Klebsiella oxytoca, and 16.3% (n = 347) other Enterobacteriaceae species. Overall, 6.8% of E coli, 10.3% of K pneumoniae, 3.7% of P mirabilis, and 11.1% of K oxytoca isolates were extended-spectrum β-lactamase−producing strains. Of the Enterobacteriaceae isolates, 67.5% were community associated and 26.9% were hospital associated (5.7% had no demographics). Highest overall rates of activity for the study period were seen with amikacin, ertapenem, and imipenem. The least active antimicrobials tested were ampicillin-sulbactam, ciprofloxacin, and levofloxacin.

Conclusions

Ertapenem, imipenem, and amikacin were the most active study drugs against extended-spectrum β-lactamase−producing strains, although the activity against extended-spectrum β-lactamase−producing K pneumoniae did not exceed 69% throughout the study period. The results of the Study for Monitoring Antimicrobial Resistance Trends surveillance study document the rates of antimicrobial resistance in UTI pathogens in the United States, which can assist health care practitioners in selecting the appropriate treatment for UTIs.