National Veterinary Institute, Technical University of Denmark, Kemitorvet, DK-2800 Kgs Lyngby, Denmark.
National Veterinary Institute, SE-751 89 Uppsala, Sweden.
Vet Microbiol. 2019 Apr;231:80-86. doi: 10.1016/j.vetmic.2019.02.032. Epub 2019 Feb 23.
The aim of the present study was to identify the animal prevalence and environmental reservoir of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) in mink farms. LA-MRSA on mink constitutes a human health hazard to farmers and farm workers, who handle the animals and are at risk of bites and scratches from colonized sites. The primary route of LA-MRSA colonization of mink is suspected to be by ingestion of contaminated pig by-products. We performed a cross-sectional study with repeated measurements during May-July 2017. A total of 644 mink carcasses (542 mink kits and 102 breeding animals) from five Danish farms were sampled. From each carcass, pharynx was swabbed and the right forepaw dissected. In addition, environmental samples covering feed, air, glove, cages (top and between) and nest boxes were collected on the farms. MRSA was selectively cultured from each sample and suspect colonies were assessed using matrix-assisted laser desorption ionisation (MALDI-TOF) for species confirmation. Further, from each farm, three isolates from mink and one isolate per positive environmental site were sent for whole genome sequencing. We isolated LA-MRSA from mink in four out of the five farms, but LA-MRSA bacterium was detected on all farms. On farms with LA-MRSA positive animals, the overall apparent animal prevalence ranged from 20% [13;29] to 29% [22;38]. LA-MRSA was isolated from kits before weaning, most likely due to a contaminated environment or transfer from the dam. Further, the apparent prevalence of LA-MRSA in kits tended to increase during the first months of age. On farms where LA-MRSA was isolated from mink, LA-MRSA was also isolated from the environment. LA-MRSA was isolated from all environmental sites tested (i.e. glove, on top of and between the cages and in the nest boxes), apart from air. The negative air samples contrast with the high concentrations of LA-MRSA in air found in the pig production. Hence, the risk of human exposure to LA-MRSA on mink-farms tends to be associated mainly with direct contact with contaminated environmental sites and the handling of colonized mink. All sequenced isolates were confirmed as LA-MRSA CC398 and genetically similar to clones previously isolated from the Danish pig production, supporting the hypothesis of LA-MRSA being transmitted by contaminated pig by-products.
本研究的目的是确定貂养殖场中与牲畜相关的耐甲氧西林金黄色葡萄球菌（LA-MRSA）的动物流行率和环境储库。貂身上的 LA-MRSA 对农民和农场工人构成了健康危害，他们处理动物，有被定植部位咬伤和划伤的风险。LA-MRSA 定植于貂的主要途径疑似是通过摄入受污染的猪副产品。我们在 2017 年 5 月至 7 月期间进行了一项横断面研究，并进行了重复测量。从丹麦五个农场的 644 只貂尸体（542 只貂幼崽和 102 只繁殖动物）中采集样本。从每只尸体的咽部分别采集拭子，并解剖右前爪。此外，还在农场收集了涵盖饲料、空气、手套、笼子（顶部和之间）和巢箱的环境样本。从每个样本中选择性培养 MRSA，并使用基质辅助激光解吸电离（MALDI-TOF）对可疑菌落进行物种确认。此外，每个农场从貂中选取三个分离株，从每个阳性环境部位选取一个分离株进行全基因组测序。我们从五个农场中的四个农场分离到 LA-MRSA，但在所有农场都检测到 LA-MRSA 细菌。在有 LA-MRSA 阳性动物的农场中，总体动物显性患病率范围为 20%[13;29]至 29%[22;38]。在断奶前从幼崽中分离出 LA-MRSA，这很可能是由于污染的环境或来自母貂的转移。此外，LA-MRSA 在幼崽中的显性患病率在头几个月的年龄增长趋势增加。在分离出 LA-MRSA 的貂的农场中，也从环境中分离出 LA-MRSA。从所有测试的环境部位（即手套、笼子顶部和之间以及巢箱）中分离出 LA-MRSA，空气除外。阴性空气样本与在猪生产中发现的高浓度 LA-MRSA 形成对比。因此，貂养殖场中人类接触 LA-MRSA 的风险似乎主要与接触污染的环境部位和处理定植的貂有关。所有测序分离株均被确认为 LA-MRSA CC398，与之前从丹麦猪生产中分离出的克隆体在遗传上相似，支持 LA-MRSA 通过受污染的猪副产品传播的假设。
