Prevalence of CTX-M-Type extended-spectrum β-lactamases in Escherichia coli strains isolated in poultry farms.

The aim of the study was to detect the prevalence of CTX-M-type extended-spectrum β-lactamases (ESBL) in Escherichia coli strains isolated in healthy chickens at poultry farms in Tenerife, Spain. From November 2012 to February 2013, 260 live chickens were screened. Samples were cultured in chromogenic media. Suspect strains were identified by Vitek 2 system and ESBL production was confirmed by the double-disk synergy test. Pulsed-field gel electrophoresis (PFGE) was performed with XbaI (Promega, Madison, WI) to ESBL-E. coli isolates. The presence of CTX-M-type was detected by real-time polymerase chain reaction. Of 260 rectal swabs, 237 (91.1%) were ESBL-E. coli, 196 (75.38%) strains were characterized by PFGE, and CTX-M-type was detected in 116 (59.1%) of these strains. With respect to the susceptibility patterns of E. coli blaCTX-M strains, 7.8% showed resistance to more than two non-β-lactam antibiotics. In our area, the prevalence of CTX-M-type in E. coli isolated in chicken was even higher than those found in other countries. The impact of food animals as a possible reservoir for ESBL-E. coli, especially CTX-M-type ESBL, and the dissemination of such strains into the food production chain need to be assessed.