Incidence of single-drug resistant, multidrug-resistant and extensively drug-resistant Escherichia coli urinary tract infections: An Australian laboratory-based retrospective study

Objectives: The aim of this study was to evaluate the incidence of single-drug resistant, multidrug-resistant (MDR), extensively drug-resistant (XDR) and pandrug-resistant (PDR) Escherichia coli urinary tract infections (UTIs) in a sample of Australian Capital Territory (ACT) residents. Methods: Laboratory-based retrospective data from all ACT residents whose urine samples were processed from January 2009 to December 2013 at ACT Pathology were utilised. Multivariate logistic regression models were constructed to determine the associations of age, sex, urine sample source and socioeconomic status with risk of resistant infections. Results: A total of 146 915 urine samples from 57 837 ACT residents were identified over 5 years. The mean ± standard deviation age of residents at first sample submitted was 48 ± 26 years, and 64.4% were female. The 5-year incidence of single-drug resistant E. coli UTI was high for ampicillin, trimethoprim and cefazolin (6.8%, 3.5% and 1.9%, respectively). No PDR E. coli UTI was detected. Five-year incidences of MDR and XDR E. coli UTIs were 1.9% and 0.2%, respectively, which is low in comparison with international rates. Female sex and age ≥38 years were significantly associated with single-drug and multidrug resistance. The risk of single-drug resistance was significantly higher in samples from after-hours general practice (GP) clinics compared with hospitals, office-hours GP clinics, and community and specialist health services (adjusted odds ratio = 2.6, 95% confidence interval 2.2–3.1). Conclusions: These findings have significant implications for antimicrobial prescribing given the identified risk factors for the detection of resistance, especially in patients attending after-hours GP clinics.