Identification of enterobacteria producing extended-spectrum beta-lactamases (ESBLs) in pig farms in Matanzas province

Abstract

Extended-spectrum beta-lactamases (ESBLs) are enzymes encoded by different genes (bla_SHV, bla_TEM, bla_CTX-M), located in plasmids, which facilitate their propagation among Gram-negative bacteria. These enzymes inactivate the beta-lactam ring of broad-spectrum, cephalosporins and monobactamic, but they are sensitive to cefamycins, carbapenems and betalactamase inhibitors. The objective of this work was to detect ESBLs-producing enterobacteria in farms and slaughterhouses in Matanzas province. Samples were collected from three pig farms and two slaughterhouses during the years 2016 and 2017. Swabs were made from different sites including animals, workers and environment; and they were grown in medium supplemented with cefotaxime. The antimicrobial susceptibility was determined by the disk diffusion method and ESBL detection by means of a screen test with indicator disks, two synergy tests with betalactamase inhibitors and by polymerase chain reaction (PCR). Forty-one enterobacteria isolates were identified, 17 of them were positive in the sieve test and 15 coincided in the synergy and PCR assays. The highest frequency was for the bla_CTX-M gene followed by the bla_TEM gene, while the bla_SHV gene was not detected. The positive ESBL isolates were found in rectal swabs (9), on surfaces (2), hands of an operator (2) and on instruments (4), only on farm A and slaughterhouse 1. Four of these isolates also presented multiresistance to quinolones, tetracyclines, and aminoglycosides. This work evidences the dissemination of positive E. coli ESBL isolates in non-clinical settings. These pig production facilities are bacteria reservoirs and resistance genes propitiating their propagation through direct contact, in the food production chain or their dissemination to the environment.