Investigation of Broad-Spectrum Beta-Lactamase Production, Antibiotic Resistance and mcr-1 Gene in Escherichia coli Isolates from Broilers

The detection of extended-spectrum beta-lactamase (ESBL) production and mobilized colistin resistance gene (mcr) in Escherichia coli isolates reveals the potential for developing bidirectional resistance to both extended-spectrum beta-lactamases and critically important colistin. The risk of transmission of these resistant bacteria from animals to humans can cause serious difficulties in terms of public health and veterinary medicine. This study was aimed to investigate the antibiotic resistance profiles of ESBLproducing E. coli isolates obtained from broilers with colibacillosis in the western part of Turkiye, the main ESBL genotypes (bla(TEM), bla(SHV), bla(OXA), bla(CTX-M)) and the mcr-1 gene, one of the important genetic determinants of colistin resistance. In the study, 247 (75%) E. coli isolates obtained by classical conventional methods from 327 colibacillosis suspected broiler livers brought to the laboratory for routine diagnosis within the scope of various studies during the last year were used. Bacterial identification was done by classical conventional methods. ESBL-producing isolates were phenotypically confirmed with CHROMagarTM ESBL. Genotypes and mcr-1 genes of ESBL-producing isolates were examined by polymerase chain reaction. Antibiotic resistance profiles of the isolates against 20 antibiotics belonging to nine antimicrobial families were evaluated by automated microbiology system (BD Phoenix, Becton- Dickinson, USA). Isolates resistant to at least one antibiotic from three or more antibiotic classes were considered as multidrug resistant (MDR). ESBL prevalence in isolates was determined as 27% (66 isolates). The most common ESBL gene was bla(TEM) (53%), and bla(CTX-M) (27%), bla(SHV) (8%) and bla(OXA) (5%) genes were also detected. All ESBL-producing isolates were determined to be MDR. All of the isolates were resistant to tigecycline, 97% to ampicillin and 91% to ciprofloxacin. The highest susceptibility was observed against amikacin, ertapenem, imipenem and meropenem (100%). In addition, the mcr-1 gene was detected in 12% of the ESBL-producing isolates. These results showed that ESBL production was high in E. coli isolates obtained from broilers, the bla(TEM) genotype was more dominant than other genotypes and the bla(TEM) genotype showed an increasing prevalence. The fact that all ESBL-producing isolates were MDR displayed the difficulty of treating these bacteria. The coexistence of ESBL and plasmid-mediated colistin resistance genes revealed that these bacteria pose a serious risk to public health.