Empirical treatment of urinary tract infections: how rational are our guidelines?

This study considers susceptibility test results obtained over a 6 month period for Enterobacteriaceae that caused urinary tract infections (UTIs) in the Cork region of Ireland and uses these results to examine the suitability of Irish empirical treatment guidelines. UTI-causing Enterobacteriaceae isolates were analysed using EUCAST guidelines to determine resistance to a set of commonly prescribed antimicrobial agents, i.e. ampicillin, amoxicillin/clavulanate, cefalexin, ciprofloxacin, nitrofurantoin and trimethoprim. Patients were categorized by age and patient type, based on origin (hospital inpatients, patients in long-term care facilities and all other non-hospitalized patients). In total, 8999 test results were analysed using the IBM Cognos Analytics Series 7 interrogation tool and Microsoft Office Excel. A variety of resistance patterns were observed. Only one antimicrobial agent, nitrofurantoin, demonstrated a resistance rate of less than 20% for all patient categories considered. Previous studies determined that a resistance rate of >20% renders an antimicrobial agent unsuitable for use as an empirical treatment option. This study demonstrated that this resistance rate is exceeded in many cases, potentially rendering some antimicrobial agents unsuitable for use as empirical treatment. We suggest that the focus on susceptibility when producing surveillance data to create empirical treatment guidelines may inadvertently camouflage resistance rates. The findings of this study highlight the need for laboratory-guided treatment of UTIs and ideally a pre-emptive sample should be obtained for laboratory investigation prior to commencement of antimicrobial therapy.