Spread of Escherichia coli Strains with High-Level Cefotaxime and Ceftazidime Resistance between the Community, Long-Term Care Facilities, and Hospital Institutions

A total of 151Escherichia coli strains resistant to cefotaxime and ceftazidime were isolated during a prospective surveillance study. These strains were characterized by clinical, microbiological, and molecular analyses and were distributed into four clusters of 103, 11, 6, and 5 isolates, along with 25 unrelated strains. The principal cluster was isolated from urine, wound, blood, and other samples in three hospitals, eight nursing homes, and a community healthcare center. This cluster was associated with both nosocomial (65%) and community-acquired (35%) infections. Most strains were resistant to ciprofloxacin, gentamicin, tobramycin, cefepime, amoxicillin-clavulanic acid, and trimethoprim-sulfamethoxazole but were susceptible to imipenem. All isolates from the four clusters expressed the extended-spectrum β-lactamase (ESBL) CTX-M-15. This enzyme was also present in 8 (30.8%) of the 26 unrelated isolates. The other ESBLs, CTX-M-14 and CTX-M-32, were detected in five and seven cases, respectively, but they were detected in individualE. coli isolates only. In three clusters,bla CTX-M-15 alleles were linked to an ISEcp1 -like element, while in eight strains of cluster II an IS26 element preceded thebla CTX-M-15 allele. An additional pool of resistance genes includedtetA ,drfA14 ordfrA17 ,sul1 orsul2 ,aac(6′)Ib , andaac(3)IIb . All except one of the 27 isolates tested for genetic virulence markers harbored the same three virulence genes:iutA andfyuA (siderophores), andtraT (serum survival factor). Epidemic or occasional isolates of cefotaxime- and ceftazidime-resistantE. coli can spread between distinct health facilities including hospitals, community health centers, and long-term care centers.