Whole-genome sequence analysis of Salmonella Infantis isolated from raw chicken meat samples and insights into pESI-like megaplasmid

• Published in: International journal of food microbiology 2021-01, Vol.337, p.108956, Article 108956
• Main Authors: Kürekci, Cemil, Sahin, Seyda, Iwan, Ewelina, Kwit, Renata, Bomba, Arkadiusz, Wasyl, Dariusz
• Format: Article
• Language: English
• Subjects: Animals; Anti-Bacterial Agents - pharmacology; Chicken meat; Chickens - microbiology; Clonal spread; Drug Resistance, Bacterial - drug effects; Drug Resistance, Bacterial - genetics; Food Microbiology; Genome, Bacterial - genetics; Megaplasmid; Phylogeny; Plasmids - drug effects; Plasmids - genetics; Poultry - microbiology; S. Infantis; Salmonella - drug effects; Salmonella - genetics; Salmonella - isolation & purification; Salmonella - pathogenicity; Salmonella Infections, Animal - epidemiology; Salmonella Infections, Animal - microbiology; Turkey - epidemiology; Virulence - genetics; Whole genome sequencing
• ISSN: 0168-1605; 1879-3460
• DOI: 10.1016/j.ijfoodmicro.2020.108956

There has been an increase in the number of reports on Salmonella enterica subsp. enterica serovar Infantis (S. Infantis) isolated from animals and humans. Recent studies using whole genome sequencing (WGS) have provided evidence on the likely contribution of a unique conjugative megaplasmid (pESI; ~280 kb) to the dissemination of this serovar worldwide. In the present study, twenty-two unrelated Salmonella strains [S. Infantis (n = 20) and Salmonella 6,7:r:- (n = 2)] and their plasmids were investigated using next generation sequencing technologies (MiSeq and MinION) to unravel the significant expansion of this bacteria in Turkey. Multi-locus sequence typing, plasmid replicons, resistance gene contents as well as phylogenetic relations between strains were determined. According to the WGS data, all S. Infantis possessed the relevant megaplasmid backbone genes and belonged to sequence type 32 (ST32) with the exception of a single novel ST7091. Tetracycline and trimethoprim/sulfamethoxazole resistance were found to be widespread in S. Infantis strains and the resistant strains exclusively carried the tetA, sul1, sul2 and dfrA14 genes. One S. Infantis isolate was also a carrier of the plasmid-mediated ampC via blaCMY-2, gene. Moreover, full genomes of four S. Infantis isolates were reconstructed based on hybrid assembly. All four strains contained large plasmids (240–290 kb) similar to previously published megaplasmid (pESI) and accompanied by several small plasmids. The megaplasmid backbone contained a toxin-antitoxin system, two virulence cassettes and segments associated with heavy metals resistance, while variable regions possessed several antibiotic resistance genes flanked by mobile elements. This study indicated that pESI-like megaplasmid is widely disseminated within the tested S. Infantis strains of chicken meat, warranting further genomic studies on clinical strains from humans and animals to uncover the overall emergence and spread of this serovar. •Investigation of megaplasmid and molecular characterization of S. Infantis strains in Turkey.•The main MLST type was ST32 and one strain having novel ST7091.•The WGS data provided the existence of mega plasmids (240–290 kb) similar to previously identified pSEI-like plasmid.•The presence of plasmid mediated blaCMY-2 gene.