Background. Escherichia coli sequence type 131 (ST131), typically fluoroquinolone-resistant (FQ-R) and/or extended-spectrum -lactamase (ESBL)-producing, has emerged globally. We assessed its prevalence and characteristics among US veterans.Methods. In 2011, 595 de-identified E. coli clinical isolates were collected systematically within 3 resistance groups (FQ-susceptible [FQ-S], FQ-R, and ESBL-producing) from 24 nationally distributed Veterans Affairs Medical Centers (VAMCs). ST131 and its H30 subclone were detected by polymerase chain reaction and compared with other E. coli for molecular traits, source, and resistance profiles.Results. ST131 accounted for 78% (184/236) of FQ-R and 64.2% (79/123) of ESBL-producing isolates, but only 7.2% (17/236) of FQ-S isolates (P <. 001). The H30 subclone accounted for ≥95% of FQ-R and ESBL-producing, but only 12.5% of FQ-S, ST131 isolates (P <. 001). By back-calculation, 28% of VAMC E. coli isolates nationally represented ST131. Overall, ST131 varied minimally in prevalence by specimen type, inpatient/outpatient source, or locale; was the most prevalent ST, followed distantly by ST95 and ST12 (13% each); and accounted for ≥40% (-lactams), >50% (trimethoprim-sulfamethoxazole, multidrug), or >70% (ciprofloxacin, gentamicin) of total antimicrobial resistance. FQ-R and ESBL-producing ST131 isolates had higher virulence scores than corresponding non-ST131 isolates. ST131 pulsotypes overlapped extensively among VAMCs.Conclusions. Among US veterans, ST131, primarily its H30 subclone, accounts for most antimicrobial-resistant E. coli and is the dominant E. coli strain overall. Possible contributors include multidrug resistance, extensive virulence gene content, and ongoing transmission. Focused attention to ST131, especially its H30 subclone, could reduce infection-related morbidity, mortality, and costs among veterans.
Bibliographical noteFunding Information:
Acknowledgments. This material is based on work supported by the Office of Research and Development, Medical Research Service, Department of Veterans Affairs (grant number 1 I01 CX000192 01 to J. R. J.), and National Institutes of Health (grant number RC4-AI092828 to E. V. S. and J. R. J.). Dave Prentiss (Minneapolis VAMC) helped prepare the figures. Mark Bielke, MD (Milwaukee VAMC, Milwaukee, WI), Jill E. Clarridge III, PhD (Puget Sound HCS VAMC and University of Washington, Seattle), Christopher Graber, MD (GLAHS-WLA campus, Los Angeles, CA), Dennis Stevens, MD (Boise VAMC, Boise, ID), and Michael Tyndale (PVAHCS, San Diego, CA) provided isolates and associated source data.
- Escherichia coli infections
- antimicrobial resistance
- extended-spectrum beta-lactamases