Epidemiology and Risk Factors for Isolation of Escherichia coli Producing CTX-M-Type Extended-Spectrum β-Lactamase in a Large U.S. Medical Center

A case-case-control study was conducted to identify independent risk factors for recovery ofEscherichia coli strains producing CTX-M-type extended-spectrum β-lactamases (CTX-ME. coli ) within a large Southeastern Michigan medical center. Unique cases with isolation of ESBL-producingE. coli from February 2010 through July 2011 were analyzed by PCR forbla CTX-M ,bla TEM , andbla SHV genes. Patients with CTX-ME. coli were compared to patients withE. coli strains not producing CTX-M-type ESBLs (non-CTX-ME. coli ) and uninfected controls. Of 575 patients with ESBL-producingE. coli , 491 (85.4%) isolates contained a CTX-M ESBL gene. A total of 319 (84.6%) patients with CTX-ME. coli (282 [74.8%] CTX-M-15 type) were compared to 58 (15.4%) non-CTX-ME. coli patients and to uninfected controls. Independent risk factors for CTX-ME. coli isolation compared to non-CTX-ME. coli included male gender, impaired consciousness, H2 blocker use, immunosuppression, and exposure to penicillins and/or trimethoprim-sulfamethoxazole. Compared to uninfected controls, independent risk factors for isolation of CTX-ME. coli included presence of a urinary catheter, previous urinary tract infection, exposure to oxyimino-cephalosporins, dependent functional status, non-home residence, and multiple comorbid conditions. Within 48 h of admission, community-acquired CTX-ME. coli (n = 51 [16%]) and non-CTX-ME coli (n = 11 [19%]) strains were isolated from patients with no recent health care contacts. CTX-ME. coli strains were more resistant to multiple antibiotics than non-CTX-ME. coli strains. CTX-M-encoding genes, especiallybla CTX-M-15 type, represented the most common ESBL determinants from ESBL-producingE. coli , the majority of which were present upon admission. Septic patients with risk factors for isolation of CTX-ME. coli should be empirically treated with appropriate agents. Regional infection control efforts and judicious antibiotic use are needed to control the spread of these organisms.