Susceptibility of Community Gram-Negative Urinary Tract Isolates to Mecillinam and Other Oral Agents

Abstract

OBJECTIVE: To determine the susceptibility of community outpatient Gram-negative urinary tract isolates to mecillinam and other commonly used oral agents.DESIGN AND SETTING: The study was a laboratory-based study of consecutive Gram-negative urinary tract isolates. Only those isolates considered to be significant pathogens were included in the study. Susceptibility testing was performed using agar dilution methodology following guidelines published by the National Committee for Clinical Laboratory Standards.POPULATION STUDIED: Outpatients presenting to a family physician or clinic with signs or symptoms suggestive of a urinary tract infection were included in the study.MAIN RESULTS: Of 2000 consecutive community isolates (91.8% Escherichia coli, 3.9% Klebsiella species, 2.0% Proteus species, 2.3% others), in vitro susceptibilities were: mecillinam 98.8%, ampicillin 77.0%, ciprofloxacin 100%, trimethoprim/sulfamethoxazole 91.6% and nitrofurantoin 95.4%. Susceptibility to mecillinam was significantly better than all other agents except ciprofloxacin (Pud_less_than0.001, McNemar's test). Organisms with reduced susceptibility to mecillinam included Citrobacter species, Pseudomonas aeruginosa and Providencia species.CONCLUSIONS: Community Gram-negative urinary tract isolates remain highly sensitive to mecillinam and ciprofloxacin, but a significant number have developed resistance to trimethoprim/sulfamethoxazole. Further studies are required to determine the clinical significance of these results.