Molecular epidemiology of extraintestinal pathogenic Escherichia coli isolates from a regional cohort of elderly patients highlights the prevalence of ST131 strains with increased antimicrobial resistance in both community and hospital care settings

Objectives: To assess the molecular epidemiology and prevalence of antibiotic resistance in Escherichia coli causing urinary tract infections of elderly patients from community and hospital settings. Also, to determine whether the possession of antibiotic resistance and virulence-associated genes can be linked to patient location or the clonal group of the organisms in question. Methods: E. coli were isolated from the urine samples of elderly patients from the Nottingham area, and subjected to antibiotic susceptibility testing, virulence gene detection by PCR and multilocus sequence typing. Results: No correlation was observed between community- or hospital-derived strains with regard to antibiotic resistance levels or virulence gene profiles. E. coli ST131 (where ST stands for sequence type) was the predominant ST found in both hospital and community samples, and demonstrated high levels of antibiotic resistance to the test panel, but did not possess a significantly larger array of virulence genes or a specific gene profile compared with other STs. Conclusions: The level of antibiotic resistance or virulence gene possession in uropathogenic E. coli is not directly associated with the healthcare setting of the patient, but there is a variation in antibiotic resistance and virulence gene possession depending on clonal group. ST131 is highly virulent and demonstrates high levels of antibiotic resistance, but its virulence does not appear to be attributable to the possession of a specific virulence-associated gene set or the possession of any virulence-associated gene in significantly higher levels than in any other ST.