High prevalence of mcr-1 encoding colistin resistance and first identification of bla(CTX-M-55) in ESBL/CMY-2-producing Escherichia coli isolated from chicken faeces and retail meat in Tunisia

摘要

Avian industries have been reported as an important contributor in the worldwide spread of antibiotic resistance owing to some particular practices especially the overuse of antibiotics. Thus in this study, we aimed to characterize extended-spectrum-beta-lactamase (ESBL) and acquired-AmpC-beta-lactamase (aAmpC)-producing Escherichia coli isolates from chicken faeces and raw meat in Tunisia. During the year 2018, 286 faecal chicken swabs and 47 raw chicken meat samples were collected and processed to recover cefotaxime-resistant E. coli. Antimicrobial susceptibility was performed by disk-diffusion and/or broth-microdilution. bla(TEM), bla(SHV), bla(CTX-M), and bla(CMY) genes were investigated by PCR/sequencing. Genes encoding resistance to colistin (mcr-1 to mcr8), tetracycline (tetA/tetB), sulfonamide (sul1/sul3), and chloramphenicol (cmlA), were analysed by PCR. Class 1 integrons were investigated by PCR/sequencing. Phylogenetic groups of all isolates were determined. PFGE and MLST were performed for representative isolates. PCR-based replicon typing was performed in mcrl-harbouring isolates. Cefotaxime-resistant E. coli was detected in 22.4% (64/286) and 63.8% (30/47) of faeces and meat samples, respectively. Ninety isolates were ESBL-producers and harboured the genes: bla(CTX-M-1) +/blc(TEM-1) (n = 65), bla(CTX-M-55) +/- bla(TEM-1) (n = 21), bla(CTX-M-14) (n = 1), and bla(SHV-12) (n = 3). The bla(CMY-2) gene was detected in four ESBL-negative isolates. Isolates belonged to phylogroups D (50%), A (36.2%), B1 (9.6%), and B2 (4.3%). Fifty-four were colistin-resistant and 52 carried the mcr-1 gene. The tetA, sull /suL3 and crnIA genes were detected among resistant isolates and 76 harboured class 1 integrons. MIST analysis revealed 13 sequence types (STs). The isolates were classified into 28 PFGE types. The IncP, IncFIB, and Inch replicons were detected among mcr-l-positive strains. We report a high frequency of ESBL-producers and colistin-resistant E. coil in chicken and derived food and the detection for the first time of bla(CTX-M-55) in poultry in Tunisia.