Introduction: The prevalence of antimicrobial resistance in urinary Escherichia coli (E. coli) is increasing in Australia but incidence and risk factors for resistance are not well described. We evaluated the incidence of antimicrobial resistant E. coli urinary tract infections (UTI) in a cohort of Australian Capital Territory (ACT) residents. The associations of age, gender and urine sample source with risk of resistant infections were also investigated.

Methods: We utilised laboratory-based retrospective data from all ACT residents who submitted urine samples to ACT Pathology between January 2009 and December 2013.

Results: A total of 146,915 urine samples from 57,837 ACT residents were identified over 5 years. The mean age of residents was 48 years (SD 26 years) with 64.4% female. The incidence of single drug resistant E. coli UTI was high for ampicillin, trimethoprim, and cefazolin (6.8%, 3.5%, and 1.9% respectively). No pandrug-resistant E. coli UTI was detected. Five year incidences of multi-drug and extensively drug-resistant E.coli UTI were 1.9% and 0.2% respectively. In multivariate logistic regressions, female age and sex over 38 years were significantly associated with single and multi-drug resistance. The risk of single-drug resistance was significantly higher in samples from after hours general practices compared to hospitals, office-hours general practices, community and specialist health services (adjusted odds ratio (OR) and 95% confidence intervals (CI) 2.6 (2.2-3.1)).

Conclusions: In this study, incidence of multi-drug and extensively drug resistant E.coli UTI are low in comparison to international rates. Our findings have significant implications for antimicrobial prescribing.