Front Microbiol 2019 8;10:1753. Epub 2019 Aug 8.
Department of Microbiology, National Veterinary Research Institute, Puławy, Poland.
The emergence of plasmid-mediated colistin resistance ( genes) threatens the effectiveness of polymyxins, which are last-resort drugs to treat infections by multidrug- and carbapenem-resistant Gram-negative bacteria. Based on the occurrence of colistin resistance the aims of the study were to determine possible resistance mechanisms and then characterize the -positive . The research used material from the Polish national and EU harmonized antimicrobial resistance (AMR) monitoring programs. A total of 5,878 commensal from fecal samples of turkeys, chickens, pigs, and cattle collected in 2011-2016 were screened by minimum inhibitory concentration (MIC) determination for the presence of resistance to colistin (R) defined as > 2 mg/L. Strains with MIC = 2 mg/L isolated in 2014-2016 were also included. A total of 128 isolates were obtained, and most (66.3%) had colistin MIC of 2 mg/L. PCR revealed in 80 (62.5%) isolates recovered from 61 turkeys, 11 broilers, 2 laying hens, 1 pig, and 1 bovine. No other -type genes (including to -) were detected. Whole-genome sequencing (WGS) of the -positive isolates showed high diversity in the multi-locus sequence types (MLST) of , plasmid replicons, and AMR and virulence genes. Generally was detected on the same contig as the IncX4 (76.3%) and IncHI2 (6.3%) replicons. One isolate harbored . on the chromosome. Various extended-spectrum beta-lactamase (, , , , , and ) and quinolone resistance genes (, , and chromosomal , and mutations) were present in the .-positive . A total of 49 sequence types (ST) were identified, ST354, ST359, ST48, and ST617 predominating. One isolate, identified as ST189, belonged to atypical enteropathogenic Our findings show that . has spread widely among production animals in Poland, particularly in turkeys and appears to be transferable mainly by IncX4 and IncHI2 plasmids spread across diverse lineages. Interestingly, most of these -positive would remain undetected using phenotypic methods with the current epidemiological cut-off value (ECOFF). The appearance and spread of among various animals, but notably in turkeys, might be considered a food chain, and public health hazard.