Clonal spread of mcr-1 in PMQR-carrying ST34 Salmonella isolates from animals in China

• Published in: Scientific reports Vol. 6; no. 1; p. 38511
• Main Authors: Li, Xing-Ping, Fang, Liang-Xing, Song, Jia-Qi, Xia, Jing, Huo, Wei, Fang, Jin-Tao, Liao, Xiao-Ping, Liu, Ya-Hong, Feng, Youjun, Sun, Jian
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 05.12.2016; Nature Publishing Group
• Subjects: 42/47; 45/22; 45/23; 45/29; 45/77; 631/1647/1513/2216; 631/326/22/1434; Ampicillin; Animals; Base Sequence; Clone Cells; Colistin; Drug Resistance, Multiple, Bacterial - genetics; Electrophoresis, Gel, Pulsed-Field; Florfenicol; Food; Genes, Bacterial; Gentamicin; Humanities and Social Sciences; Microbial Sensitivity Tests; Molecular Typing; multidisciplinary; Nalidixic acid; Plasmids; Plasmids - metabolism; Salmonella; Salmonella Infections, Animal - microbiology; Salmonella typhimurium - genetics; Salmonella typhimurium - isolation & purification; Science; Streptomycin; Trimethoprim; China
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep38511

Since initial identification in China, the widespread geographical occurrence of plasmid-mediated colistin resistance gene mcr-1 in Enterobacteriaceae has been of great concern. In this study, a total of 22 Salmonella enterica were resistant to colistin, while only five isolates which belonged to ST34 Salmonella enterica serovar Typhimurium ( S. Typhimurium) were mcr-1 positive. Four of them shared nearly identical PFGE type, although they were from different host species and diverse geographical locations. All the mcr-1 -positive S. Typhimurium exhibited multi-resistant phenotypes including ampicillin, streptomycin, gentamicin, florfenicol, nalidixic acid, tetracycline, trimethoprim-sulfamethox, in addition to colistin. The oqxAB and aac ( 6 ′) -Ib-cr genes were present alone or in combination in four (80.0%) and five (100%) isolates, respectively. The mcr-1 gene was located on a transferable IncI2 plasmid in the four genetically related strains. In the other one strain, mcr-1 was located on an approximately 190 kb IncHI2 plasmid. In conclusion, we report five mcr-1- positive S. Typhimurium/ST34 isolates. Both clonal expansion and horizontal transmission of IncI2-type plasmids were involved in the spread of the mcr-1 gene in Salmonella enterica from food-producing animals in China. There is a great need to monitor the potential dissemination of the mcr-1 gene.