We have identified CTX-M group 1 β-lactamases in 87% of community-acquired Escherichia coli isolates that produce extended-spectrum β-lactamases, with the majority harboring CTX-M-15 and representing the ST131 clonal group. Seventy percent of CTX-M-bearing isolates were from urine specimens; a large proportion was nonsusceptible to levofloxacin, trimethoprim/sulfamethoxazole, and β-lactam antimicrobials. Many patients were relatively youthful (41% ≤65 years old; youngest, age 32). Patients with symptomatic bacteriuria received drugs to which the organisms were susceptible, and most had favorable outcomes. Timely recognition of such isolates could help physicians choose more appropriate antibacterial therapy.
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