Lienen Tobias, Schnitt Arne, Hammerl Jens Andre, Maurischat Sven, Tenhagen Bernd-Alois
Department of Biological Safety, German Federal Institute for Risk Assessment, Berlin, Germany.
Front Microbiol. 2021 Jan 8;11:575321. doi: 10.3389/fmicb.2020.575321. eCollection 2020.
Methicillin-resistant (MRSA) have been found on German dairy farms and may be the cause of difficult-to-treat bovine mastitis. Considering the one health approach, MRSA might be transmitted from animals to humans raising the risk for severe infections. On 17 German dairy farms with a history of MRSA detection, MRSA strains were isolated from quarter milk, bulk tank milk, and swab samples of calves, heifers, pigs, and the environment. A selection of 33 isolates was analyzed using whole-genome sequencing and antimicrobial resistance testing. All detected MRSA strains were attributed to the livestock-associated sequence type 398. Methicillin-resistance was associated with the gene in the staphylococcal cassette chromosome (SCC) types IVa (7/33) or V (26/33). The MRSA strains across the German federal states showed large allelic differences indicating independent development and distribution. On one farm, a clonal MRSA isolate was widely spread among different animals and the milking equipment. Moreover, MRSA transmission between two dairy farms in one federal state seems to be likely. In depth studies indicated that the resistance gene prediction and phenotypic resistance are in good agreement. Twenty eight strains were determined to exhibit a non-wildtype phenotype (resistant) against up to seven antimicrobial substances with an overall resistance to β-lactams and tetracycline. Ten different phenotypic antimicrobial resistance patterns were found among the MRSA strains. The strains harbored a wide virulence gene repertoire, of which some of them are related to bovine mastitis. However, the isolates lacked typical human infection associated factors such as the immune evasion cluster genes, staphylococcal enterotoxin genes, or Panton-Valentine leukocidin genes leading to the assumption for a low risk for severe human infections and foodborne diseases.
在德国奶牛场发现了耐甲氧西林金黄色葡萄球菌（MRSA），它可能是导致难以治疗的牛乳腺炎的原因。考虑到“同一健康”方法，MRSA可能会从动物传播给人类，从而增加严重感染的风险。在17个有MRSA检测历史的德国奶牛场，从奶牛的单个乳区牛奶、奶罐牛奶以及犊牛、小母牛、猪的拭子样本和环境中分离出了MRSA菌株。使用全基因组测序和抗菌药物耐药性测试对33株分离株进行了分析。所有检测到的MRSA菌株都属于与牲畜相关的序列类型398。耐甲氧西林与葡萄球菌盒式染色体（SCC）IVa型（7/33）或V型（26/33）中的基因相关。德国各联邦州的MRSA菌株显示出较大的等位基因差异，表明其是独立发展和传播的。在一个农场中，一株克隆性MRSA分离株在不同动物和挤奶设备中广泛传播。此外，在一个联邦州的两个奶牛场之间似乎很可能存在MRSA传播。深入研究表明，耐药基因预测与表型耐药性高度一致。28株菌株被确定对多达七种抗菌物质表现出非野生型表型（耐药），总体上对β-内酰胺类和四环素耐药。在MRSA菌株中发现了十种不同的表型抗菌耐药模式。这些菌株具有广泛的毒力基因库，其中一些与牛乳腺炎有关。然而，这些分离株缺乏典型的与人类感染相关的因素，如免疫逃避簇基因、葡萄球菌肠毒素基因或杀白细胞素基因，因此推测其导致严重人类感染和食源性疾病的风险较低。
