Fluoroquinolone-resistant Escherichia coli sequence type 131 isolates causing bloodstream infections in a canadian region with a centralized laboratory system: rapid emergence of the H30-Rx sublineage.

A population-based surveillance study was designed to describe the clinical features and characteristics of sequence type 131 (ST131) and its H30 and H30-Rx sublineages among fluoroquinolone-resistant (FQ-R) Escherichia coli isolates that caused bloodstream infections (BSIs) in a Canadian region with a centralized laboratory system over an 11-year period (2000 to 2010). Nonrepeat isolates from true incident cases were included. Established PCR methods were used to define ST131, its H30 and H30-Rx sublineages, extended-spectrum β-lactamase and AmpC production, and plasmid-mediated quinolone resistance determinants. A total of 677 Calgary residents with incident BSIs due to FQ-R E. coli were identified; the majority presented with health care-associated upper urinary tract infections (UTIs). There was a rise in FQ-R over the 11-year period because of an increase in ST131 toward the end of the study period (2008 to 2010) that was due to a rapid influx of the H30-Rx sublineage. We identified the association of H30-Rx with primary sepsis, upper UTIs as a complication of prostate biopsies, multidrug resistance, and the presence of blaCTX-M-15 and aac(6')-lb-cr. E. coli ST131 H30-Rx has established itself as a major drug-resistant sublineage in Calgary, posing an important new public health threat within our region. We urgently need well-designed epidemiological and molecular studies to further understand the dynamics of transmission, risk factors, and reservoirs of H30-Rx.