Escherichia coli sequence type 131 H30 is the main driver of emerging extended-spectrum-β-lactamase-producing E. coli at a tertiary care center

The H30 strain of Escherichia coli sequence type 131 (ST131-H30) is a recently emerged, globally disseminated lineage associated with fluoroquinolone resistance and, via its H30Rx subclone, the CTX-M-15 extended-spectrum betalactamase (ESBL). Here, we studied the clonal background and resistance characteristics of 109 consecutive recent E. coli clinical isolates (2015) and 41 historical ESBLproducing E. coli blood isolates (2004 to 2011) from a public tertiary care center in California with a rising prevalence of ESBL-producing E. coli isolates. Among the 2015 isolates, ST131, which was represented mainly by ST131-H30, was the most common clonal lineage (23% overall). ST131-H30 accounted for 47% (8/17) of ESBLproducing, 47% (14/30) of fluoroquinolone-resistant, and 33% (11/33) of multidrugresistant isolates. ST131-H30 also accounted for 53% (8/14) of dually fluoroquinoloneresistant, ESBL-producing isolates, with the remaining 47% comprised of diverse clonal groups that contributed a single isolate each. ST131-H30Rx, with CTX-M-15, was the major ESBL producer (6/8) among ST131-H30 isolates. ST131-H30 and H30Rx also dominated (46% and 37%, respectively) among the historical ESBL-producing isolates (2004 to 2011), without significant temporal shifts in relative prevalence. Thus, this medical center's recently emerging ESBL-producing E. coli strains, although multiclonal, are dominated by ST131-H30 and H30Rx, which are the only clonally expanded fluoroquinolone-resistant, ESBL-producing lineages. Measures to rapidly and effectively detect, treat, and control these highly successful lineages are needed.