Escherichia coli sequence type 131 (ST131) subclone H30 as an emergent multidrug-resistant pathogen among US veterans.
BACKGROUND
Escherichia coli sequence type 131 (ST131), typically fluoroquinolone-resistant (FQ-R) and/or extended-spectrum β-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% (β-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.
University of Minnesota, Minneapolis.
Aylin
A
Colpan
Brian
B
Johnston
Stephen
S
Porter
Connie
C
Clabots
Ruth
R
Anway
Lao
L
Thao
Michael A
MA
Kuskowski
Veronika
V
Tchesnokova
Evgeni V
EV
Sokurenko
James R
JR
Johnson
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D024901:Drug Resistance, Multiple, Bacterial; D004926:Escherichia coli / Q000145:classification* / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000453:epidemiology* / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000235:genetics; D024841:Fluoroquinolones / Q000494:pharmacology; D005838:Genotype; D006801:Humans; D017720:Molecular Epidemiology; D058889:Molecular Typing; D016133:Polymerase Chain Reaction; D015995:Prevalence; D014481:United States / Q000453:epidemiology; D014728:Veterans; D037521:Virulence Factors / Q000235:genetics; D047090:beta-Lactams / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; D024841:Fluoroquinolones; D037521:Virulence Factors; D047090:beta-Lactams
Escherichia coli infections; ST131; antimicrobial resistance; extended-spectrum beta-lactamases; veterans