The Niche for Escherichia coli Sequence Type 131 Among Veterans: Urinary Tract Abnormalities and Long-Term Care Facilities

Abstract

Background. Antimicrobial resistance among Escherichia coli is increasing, driven largely by the global emergence of sequence type 131 (ST131). However, the clinical significance of ST131 status is unknown. Among veterans, we assessed whether ST131 causes more severe, persistent, or recurrence-prone infections than non-ST131 E. coli. Methods. Isolates were assessed by polymerase chain reaction for membership in ST131 and relevant subclones thereof (H30R and H30Rx) and by broth microdilution for susceptibility to 11 antibiotics. Clinical and epidemiological data were systematically abstracted from the medical record. Between-group comparisons were made using t tests and Fisher's exact test. Results. Of the 311 unique E. coli isolates, 61 (19.6%) represented ST131. Of these, most (51 of 61, 83.6%) represented the H30R subclone; only 5 of 51 (9.8%) represented H30Rx. Relative to non-ST131 and non-H30R isolates, neither ST131 nor H30R were associated with more severe disease, worse clinical outcomes, or more robust hosts. Instead, both were more likely to be isolated from patients without manifestations of infection (for ST131, 36.1% vs 21.2% [P = .02]; for H30R, 39% vs 21% [P = .008]) and who had prior healthcare contact or long-term care facility (LTCF) exposure (for ST131, 33% vs 14% [P = .002]; for H30R, 37% vs 14% [P < .001]). Despite a greater likelihood of discordant initial therapy, outcomes did not differ between ST131 and H30R isolates vs other E. coli isolates. Conclusions. Among veterans, ST131 and its H30R subclone were associated with LTCF-exposed hosts but not with worse outcomes.

Keywords: Escherichia coli; antimicrobial resistance; epidemiology; virulence.