Escherichia coli sequence type ST131 (from phylogenetic group B2), often carrying the extended-spectrum-β-lactamase (ESBL) gene bla CTX-M-15, is an emerging globally disseminated pathogen that has received comparatively little attention in the United States. Accordingly, a convenience sample of 351 ESBL-producing E. coli isolates from 15 U.S. centers (collected in 2000 to 2009) underwent PCR-based phylotyping and detection of ST131 and bla CTX-M-15. A total of 200 isolates, comprising 4 groups of 50 isolates each that were (i) bla CTX-M-15 negative non-ST131, (ii) bla CTX-M-15 positive non-ST131, (iii) bla CTX-M-15 negative ST131, or (iv) bla CTX-M-15 positive ST131, also underwent virulence genotyping, antimicrobial susceptibility testing, and pulsed-field gel electrophoresis (PFGE). Overall, 201 (57%) isolates exhibited bla CTX-M-15, whereas 165 (47%) were ST131. ST131 accounted for 56% of bla CTX-M-15-positive-versus 35% of bla CTX-M-15-negative isolates (PCTX-M-15 status, with groups A (bla CTX-M-15-positive isolates) andD(bla CTX-M-15- negative isolates) predominating. Both bla CTX-M-15 and ST131 occurred at all participating centers, were recovered from children and adults, increased significantly in prevalence post-2003, and were associated with molecularly inferred virulence. Compared with non- ST131 isolates, ST131 isolates had higher virulence scores, distinctive virulence profiles, and more-homogeneous PFGE profiles. bla CTX-M-15 was associated with extensive antimicrobial resistance and ST131 with fluoroquinolone resistance. Thus, E. coli ST131 and bla CTX-M-15 are emergent, widely distributed, and predominant among ESBL-positive E. coli strains in the United States, among children and adults alike. Enhanced virulence and antimicrobial resistance have likely promoted the epidemiological success of these emerging public health threats.
All Science Journal Classification (ASJC) codes
- Pharmacology (medical)
- Infectious Diseases