Characterisation of ESBL-producing E. coli isolated from healthy broilers in Tunisia

Abstract

The aim of this study was to investigate the frequency of antimicrobial resistance and the rate of extended-spectrum β-lactamase (ESBL) in Escherichia coli isolated from caecum content collected in slaughterhouses located in three regions of Tunisia. E. coli isolates from chicken caecal samples, obtained using media supplemented with cefotaxime, were screened for antimicrobial susceptibility by the disk diffusion method. ESBL production was assessed by the double-disk synergy test, and the presence of β-lactamase encoding resistance genes was evaluated by PCR. Out of 111 faecal samples, 108 samples were positive for E. coli isolated from media supplemented with cefotaxime with 70% of ESBL-producing isolates. Alarming proportions of resistance against most of the 21 tested antibiotics were observed with 90% of multidrug resistant strains. Most strains exhibited resistance to amoxicillin, cefepime, tetracycline, cephalothin, piperacillin, cefotaxime, aztreonam, streptomycin, ceftazidime, cefuroxime, chloramphenicol, and florfenicol. The same resistance patterns were found in comparison between the three chicken slaughterhouses. A high prevalence of β-lactamase genes was observed, with blaCTX-M-G1-ESBLin 79.6% of strains,bla TEMin 45.4%, andbla SHV in 33.3%. The blaCTX-M-G1 and blaTEM genes were significantly more frequent in strains from slaughterhouses A and C. Additionally, carbapenem resistance genes, blaOXA-48 and blaIMP, were demonstrated in 13% and 6.5% of strains, respectively. The study showed high frequency of ESBL-producing E. coli and high antibiotic resistance in broilers. Poultry farms could represent a significant reservoir of ESBL-producing bacteria, suggesting the dissemination of these pathogens to humans and environment. These findings indicate the need for achievement of control and surveillance system.