Department of Food Hygiene and Technology, Faculty of Veterinary Medicine, Hatay Mustafa Kemal University, Hatay 31030, Turkey.
Department of Food Hygiene and Technology, Faculty of Veterinary Medicine, Sivas Cumhuriyet University, Sivas 58140, Turkey.
Int J Food Microbiol. 2021 Jan 16;337:108956. doi: 10.1016/j.ijfoodmicro.2020.108956. Epub 2020 Nov 6.
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 bla, 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.
从动物和人类中分离出的肠炎沙门氏菌亚种肠炎沙门氏菌血清型 Infantis（S. Infantis）的报告数量有所增加。最近使用全基因组测序（WGS）的研究为该血清型在全球传播的独特可转移大质粒（pESI；~280kb）的可能贡献提供了证据。在本研究中，使用下一代测序技术（MiSeq 和 MinION）对 22 株无关的沙门氏菌菌株[S. Infantis（n=20）和沙门氏菌 6,7:r:-（n=2）]及其质粒进行了研究，以揭示该细菌在土耳其的显著扩张。进行了多位点序列分型、质粒复制子、耐药基因含量以及菌株之间的系统发育关系分析。根据 WGS 数据，所有 S. Infantis 都具有相关的大质粒骨架基因，属于序列型 32（ST32），除了一个单一的新型 ST7091 外。四环素和甲氧苄啶/磺胺甲恶唑耐药在 S. Infantis 菌株中广泛存在，耐药菌株仅携带 tetA、sul1、sul2 和 dfrA14 基因。一株 S. Infantis 分离株还携带质粒介导的 ampC 通过 bla 基因。此外，基于混合组装重建了 4 株 S. Infantis 分离株的全基因组。所有 4 株菌都含有类似于先前发表的大质粒（pESI）的大型质粒（240-290kb），并伴有几个小质粒。大质粒骨架包含一个毒素-抗毒素系统、两个毒力盒和与重金属耐药性相关的片段，而可变区则含有几个抗生素耐药基因，侧翼为移动元件。本研究表明，pESI 样大质粒在测试的鸡肉源 S. Infantis 菌株中广泛传播，需要对来自人类和动物的临床菌株进行进一步的基因组研究，以揭示该血清型的整体出现和传播。
