Incidence of single-drug-, multidrug-, and extensively drug-antimicrobial resistance of Escherichia coli urinary tract infections: an Australian laboratory-based retrospective study.

OBJECTIVES: To evaluate incidence of single-drug resistant, multidrug-resistant, extensively drug-resistant and pandrug-resistant E. coli urinary tract infections (UTI) in a sample of Australian Capital Territory (ACT) residents.

METHODS: We utilised laboratory-based retrospective data from all ACT residents whose urine samples were processed from January 2009 to December 2013. 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 five years. Mean age of people in the sample was 48 years (standard deviation=26years) and 64.4% were females. Five-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 pandrug-resistant E. coli UTI was detected. Five-year incidences of multidrug- and extensively drug-resistant E. coli UTI were 1.9% and 0.2% respectively, which is low in comparison to international rates. Female sex and age over 38 years were significantly associated with single- and multidrug-resistance. Compared to hospitals, office-hours general practices, community and specialist health services, risk of single-drug resistance was significantly higher in samples from after-hours general practices (adjusted-odds ratio (OR) and 95% confidence intervals (CI) 2.6 (2.2-3.1)).

CONCLUSIONS: Our findings have significant implications for antimicrobial prescribing given identified risk factors for the detection of resistance, especially in patients attending after-hours general practices.