Characterization of cefoxitin-resistant Escherichia coli isolates from recreational beaches and private drinking water in Canada between 2004 and 2006.

A total of 142 cefoxitin-resistant Escherichia coli isolates from water sources were collected across Canada. Multidrug resistance was observed in 65/142 (45.8%) isolates. The bla(CMY-2) gene was identified in 110/142 (77.5%) isolates. Sequencing of the chromosomal ampC promoter region showed mutations from the wild type, previously shown to hyperproduce AmpC. CMY-2-producing plasmids predominantly belonged to replicon groups I1-Igamma, A/C, and K/B. The majority of the E. coli isolates belonged to the nonvirulent phylogenetic groups A and B1.