Occurrence and Characterisation of Colistin-Resistant in Raw Meat in Southern Italy in 2018-2020.

Colistin is a last-resort drug for the treatment of infections by carbapenem-resistant , and the emergence of colistin resistance poses a serious clinical challenge. The aim of this study was to investigate the occurrence of colistin-resistant in retail meat in Southern Italy in 2018-2020. Of 570 samples, 147 contained . Two out of 147 (1.4%) showed a non-wild-type phenotype to colistin and harboured . was also detected in a wild-type isolate, resulting in a 2% prevalence. -positive isolates originated from turkey meat collected in Apulia (n = 2) and Basilicata (n = 1). A whole-genome sequencing analysis confirmed and in two and one isolate, respectively. The strains were diverse, belonging to three multi-locus sequence types (ST354, ST410, SLV of ST10) and harbouring genes mediating resistance to antimicrobials in two, six and seven classes. was carried by IncX4 plasmids with high nucleotide similarity to IncX4 plasmids harbouring and in from different sources and geographical regions. This is the first study reporting updates on non-wild-type to colistin from retail meat in Southern Italy, highlighting the importance of phenotypic and genotypic antimicrobial resistance surveillance to contain the dissemination of among .