Emergence of and risk factors for ciprofloxacin-gentamicin-resistant Escherichia coli urinary tract infections in a region of Quebec.

BACKGROUND: An increased incidence of urinary tract infections (UTIs) caused by ciprofloxacin-gentamicin-resistant Escherichia coli (CiGREC) has been observed in a tertiary care centre in Sherbrooke, Quebec. The risk factors for such infections remained unclear. METHODS: To determine risk factors for, and outcomes of, CiGREC UTIs, a case control study was conducted. Between 2000 and 2007, 93 cases and 186 controls were identified using laboratory records of patients with greater than 10(7) colony-forming units/L of E coli in a urinary specimen. Cases had E coli with minimum inhibitory concentration to ciprofloxacin of 4 mg/L or greater and minimum inhibitory concentration to gentamicin of 8 mg/L or greater (CiGREC), and controls had E coli with any other susceptibility pattern to ciprofloxacin and gentamicin. Clinical and laboratory data were collected. Adjusted odds ratios (AOR) and their 95% CIs were calculated by logistic regression. RESULTS: The prevalence of CiGREC increased sixfold during the study period. Risk factors associated with CiGREC UTI were advanced age, male sex, urological abnormality, domicile outside Sherbrooke, living in a nursing home (AOR 11.73; 95% CI 3.70 to 37.15), use of fluoroquinolones (AOR 15.24; 95% CI 5.42 to 42.83) or aminoglycosides (AOR 6.59; 95% CI 1.22 to 35.61) within the previous month, and use of fluoroquinolones during the preceding one to 12 months (AOR 2.45; 95% CI 1.06 to 5.62). Compared with controls, cases were more likely not to receive an active antibiotic as empirical or definitive treatment, and were more likely to relapse. INTERPRETATION: In the future, it may become necessary to avoid selecting as empirical therapy of urinary tract infection an antibiotic to which the patient has been recently exposed.