LAUSR

INTRODUCTION Colistin is considered last resort antibiotic against carbapenem-resistant isolates. Nowadays, this antibiotic is facing the emergence of mobilised colistin resistance (mcr) genes which confer colistin resistance. OBJECTIVE Genomic characterisation of an atypical multidrug-resistant Escherichia coli harbouring two mcr genes in France. Samples collected from a pig farm in Avignon (Vaucluse department) were subjected to molecular screening targeting mcr variants. MATERIALS AND METHODS Samples were cultured on selective Lucie-Bardet-Jean-Marc-Rolain medium (LBJMR). Growing bacteria were identified using MALDI-TOF, followed by antibiotic susceptibility testing (AST). Whole genome sequencing (WGS) and bioinformatic genome analysis was performed. RESULTS Selective culture of stools revealed the presence of an E. coli strain named Q4552 harbouring mcr-1.1 and mcr-3.5 genes which is also resistant to fourteen antibiotics. Genome sequencing and assembly resulted to a complete and circular chromosome and eight different plasmids. Sequence analysis demonstrated an integration of a mobile genetic element (MGE) carrying mcr-1.1 in the chromosome while mcr-3.5 gene was in the plasmid and its resistome was composed of twenty-two resistance genes. Q4552 strain was identified as an ST-843 clone which belonged to the clonal complex Cplx-568 and is the only ST type of this cplx-568 which has been isolated from animals, humans, and the environment. CONCLUSION We report the first co-occurrence of mcr-1 and mcr-3 genes in France from a pathogenic E. coli isolated from a pig. Since this clone (ST-843) has been reported in zoonotic transmissions, programs to monitor such bacterium are urgently required to avoid its spread and zoonotic transmission to humans.