NEW YORK (Reuters Health) – Escherichia coli is responsible for an increasing proportion of urinary tract infections and is showing more resistance to antimicrobials, Irish researchers report in an August 24th on-line paper in BJU International.
Moreover, Dr. Ivor M. Cullen told Reuters Health by email, “The dramatic 11-year rate increase in gentamicin resistance is of paramount concern.”
Dr. Cullen and colleagues at Adelaide and Meath Hospital, Dublin conducted a retrospective analysis of more than 42,000 E. coli urine isolates from a single teaching hospital between 1999 and 2009.
These were from inpatients with nosocomial urinary tract infection (UTIs), urine from the emergency department and general practice patients and UTIs in urology patients. Over the study period, the incidence of E. coli UTIs rose from 50% to 60%.
Those in urology patients showed higher antibiotic resistance rates than the others.
Altogether, said Dr. Cullen, “There were significant trends of increasing resistance over the 11-year period for ampicillin, trimethoprim, gentamicin and ciprofloxacin, and significant differences in co-amoxyclav, gentamicin, nitrofurantion and ciprofloxacin resistance rates depending on the sample origin.”
The resistance rate for ampicillin was 58.3% and for trimethoprim, it was 33.8%. These were the least active agents indicating that they are no longer appropriate first-line empirical therapies.
The overall gentamicin resistance rate was 3.4% and, although still low, was climbing at a rate of 0.7% per year. In urology patients the resistance rate was 6.4%. Gentamicin, the team point out, “is the antibiotic of choice used in local operative urology prophylaxis.”
Nitrofuran remained effective in all 3 groups and there was no significant change in resistance over the study period.
“Neither penicillins nor trimethoprim represent suitable empirical antibiotic agents for UTI,” stressed Dr. Cullen, “and ciprofloxacin resistance in this… study renders it unsuitable empirical therapy for nosocomial UTIs and UTIs in the urology population.”
There has been over-reliance on ciprofloxacin, and although there are no Irish guidelines, say the investigators, the study clearly indicates that nitrofurantoin with an overall resistance rate of 2.1% and cephalosporins with a rate of 2.6% are appropriate empirical first-line agents.