Reservoirs of CTX-M extended spectrum β-lactamase-producing Enterobacteriaceae in Oaxaca, Mexico

Abstract

Objectives: To investigate putative reservoirs of CTX-M extended spectrum β-lactamase- producing Enterobacteriaceae (ESBL-E) in Oaxaca, Mexico. Methods: Samples from different putative reservoirs of these organisms were analyzed and included human and dog feces, tap water, fresh beef and chicken meat, salsas and vegetables from street vendors and domestic flies in household kitchens and restaurants. Identification of ESBL-E was performed according to CLSI guidelines; molecular characterization of bla CTX-M strains was performed using PCR. Results: Except for tap water, all the analyzed niches act as reservoir of ESBL-E clones in our community. The prevalence of either ESBL-E contamination or colonization varies depending on the reservoir under study, from very high (78/104) in human fecal carriage to non-existent (0/30) in tap water; 96.2% (150/156) of the ESBL-E positive clones harbored the bla CTX-M gene. Conclusions: Contamination or fecal colonization of ESBL-E clones in our community is largely spread and our results suggest that, if overuse of antibiotics plays a key role in the appearance of antibacterial resistance clones, the lack of hygiene measures may play a pivotal role in the spread of ESBL-E to humans.