Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, Saint Paul.
Department of Veterinary Medicine, University of Cambridge, United Kingdom.
Clin Infect Dis. 2018 Mar 5;66(6):877-885. doi: 10.1093/cid/cix909.
Salmonella 4,[5],12:i:-, a worldwide emerging pathogen that causes many food-borne outbreaks mostly attributed to pig and pig products, is expanding in the United States.
Whole-genome sequencing was applied to conduct multiple comparisons of 659 S. 4,[5],12:i:- and 325 Salmonella Typhimurium from different sources and locations (ie, the United States and Europe) to assess their genetic heterogeneity, with a focus on strains recovered from swine in the US Midwest. In addition, the presence of resistance genes and other virulence factors was detected and the antimicrobial resistance phenotypes of 50 and 22 isolates of livestock and human origin, respectively, was determined.
The S. 4,5,12:i:- strains formed two main clades regardless of their source and geographic origin. Most (84%) of the US isolates recovered in 2014-2016, including those (48 of 51) recovered from swine in the US Midwest, were part of an emerging clade. In this clade, multiple genotypic resistance determinants were predominant, including resistance against ampicillin, streptomycin, sulfonamides, and tetracyclines. Phenotypic resistance to enrofloxacin (11 of 50) and ceftiofur (9 of 50) was found in conjunction with the presence of plasmid-mediated resistance genes (qnrB19/qnrB2/qnrS1 and blaCMY-2/blaSHV-12, respectively). Higher similarity was also found between S. 4,[5],12:i:- from the emerging clade and S. Typhimurium from Europe than with S. Typhimurium from the United States.
Salmonella 4,[5],12:i:- currently circulating in swine in the US Midwest are likely to be part of an emerging multidrug-resistant clade first reported in Europe, and can carry plasmid-mediated resistance genes that may be transmitted horizontally to other bacteria, and thus may represent a public health concern.
沙门氏菌 4,[5],12:i:-, 一种在全球范围内引起许多食源性疾病爆发的新兴病原体，主要与猪和猪产品有关，在美国不断蔓延。
对 659 株来自不同来源和地点（即美国和欧洲）的沙门氏菌 4,[5],12:i:-和 325 株沙门氏菌 Typhimurium 进行全基因组测序，以评估其遗传异质性，重点是从美国中西部猪中分离出的菌株。此外，还检测了耐药基因和其他毒力因子的存在，并确定了 50 株和 22 株来自牲畜和人类来源的分离株的抗菌药物表型。
无论其来源和地理来源如何，S. 4,5,12:i:-菌株都形成了两个主要分支。2014-2016 年期间在美国分离的大多数（84%）菌株，包括来自美国中西部猪的 48 株菌株，都属于一个新兴的分支。在这个分支中，多种基因型耐药决定因素占主导地位，包括对氨苄西林、链霉素、磺胺类药物和四环素的耐药性。同时还发现了对恩诺沙星（50 株中的 11 株）和头孢噻呋（50 株中的 9 株）的表型耐药性，与质粒介导的耐药基因（qnrB19/qnrB2/qnrS1 和 blaCMY-2/blaSHV-12）的存在有关。与来自美国的沙门氏菌 Typhimurium 相比，新兴分支中的 S. 4,[5],12:i:-菌株与来自欧洲的沙门氏菌 Typhimurium 之间的相似性更高。
目前在美国中西部猪中流行的沙门氏菌 4,[5],12:i:-菌株可能是首次在欧洲报道的一个新兴多药耐药分支的一部分，并且可能携带可水平传播给其他细菌的质粒介导的耐药基因，因此可能构成公共卫生关注。
