Molecular analysis of bla(SHV), bla(TEM), and bla(CTX-M) in extended-spectrum β-lactamase producing Enterobacteriaceae recovered from fecal specimens of animals

Colonization of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae as animal gut microbiota is a substantial global threat. This study aimed to determine the molecular characterization of bla(SHV), bla(TEM), and bla(CTX-M) variants in animals, as well as to evaluate the antimicrobial resistance conferred by these genes. We prospectively analyzed 1273 fecal specimens of farm and domestic animals for the isolation of enterobacteria that had the ESBL phenotype by using biochemical methods. The extracted genes were amplified by polymerase chain reaction and sequenced for the characterization of bla(SHV), bla(TEM), and bla(CTX-M) variants. The drug-resistance spectrum and hierarchical clusters were analyzed against 19 antibacterial agents. Out of 245 (19.2%) ESBL enterobacteria, 180 (75.5%) Escherichia coli and 34 (13.9%) Klebsiella pneumoniae were prevalent species. A total of 73.9% bla(CTX-M), 26.1% bla(TEM), and 14.2% bla(SHV) were found among the enterobacteria; however, their association with farm or domestic animals was not statistically significant. The distribution of bla gene variants showed the highest number of bla(CTX-M-1) (133; 54.3%), followed by bla(CTX-M-15) (28; 11.4%), bla(TEM-52) (40; 16.3%), and bla(SHV-12) (22; 9%). In addition, 84.5% of the enterobacteria had the integrons intI1. We observed ±100% enterobacteria resistant to cephalosporin, 7 (2.9%) to colistin (minimum inhibitory concentration breakpoint ≥4 μg/mL), 9 (3.7%) to piperacillin-tazobactam, 11 (4.5%) to imipenem, 14 (5.7%) to meropenem, and 18 (7.3%) to cefoperazone-sulbactam, without statistically significant association. Animal gut microbiota contain a considerable number of bla(CTX-M), bla(TEM), bla(SHV), and integrons, which are a potential source of acquired extensive drug resistance in human strains and leaves fewer therapeutic substitutes.