Prevalence and characteristics of multidrug-resistant Escherichia coli sequence type ST131 at two academic centers in Boston and Minneapolis, USA

•E. coli sequence type 131 accounts for many extraintestinal E. coli infections.•315 urine isolates from two medical centers in Minneapolis and Boston were compared.•Isolates exhibited predominantly B2 phylogenetic group and comparable ST131 prevalence.•Virulence genotypes varied significantly in relation to center and ST131 status.•The emerging C1-M27 subclone occurred uniquely among 6% of Boston isolates. Escherichia coli sequence type (ST) ST131, with its emergent resistance-associated H30Rx, H30R1, and C1-M27 clonal subsets, accounts for the greatest share of extraintestinal E. coli infections and most extended-spectrum β-lactamase (ESBL)-producing E. coli. We characterized and compared consecutive E. coli urine isolates from two geographically distinct medical centers in Minneapolis, Minnesota (n = 172) and Boston, Massachusetts (n = 143) for ESBL phenotype, CTX-M-type ESBL genes, phylogenetic groups, selected ST131 subclones, and 40 extraintestinal virulence genes. Whereas the Boston vs. Minneapolis isolates had a similar prevalence of phylogenetic groups (mainly B2: 79% vs 73%), ST131 (34% vs 28%), H30 (28% vs 21%), and H30Rx (6% vs 5%), the emerging C1-M27 subclone occurred uniquely among Boston (6%) isolates. ESBL production was more prevalent among Boston isolates (15% vs 8%) and among ST131 isolates. Identified ESBL genes included blaCTX-M-27 (Boston only) and blaCTX-M-15. Ciprofloxacin resistance was ST131-associated and similarly prevalent across centers. Boston isolates had higher virulence gene scores. Despite numerous similarities to Minneapolis isolates, Boston ST131 isolates demonstrated more prevalent ESBL production, higher virulence gene scores, and, uniquely, the C1-M27 subclone and blaCTX-M-27. Broader surveillance is needed to define the prevalence of ST131′s globally successful C1-M27 subclone across the U.S.