摘要

      金黄色葡萄球菌属和非金黄色葡萄球菌属（NAS）是世界各地奶牛乳房炎的常见病原。由于金黄色葡萄球菌多药耐药率上升，目前使用抗菌药物的治疗受到越来越多的关注。本研究的目的是确定：（1）中国大型奶牛场临床乳腺炎中分离到的葡萄球菌的遗传多样性；（2）这些分离物中抗微生物基因（ARG）的流行和分布。金黄色葡萄球菌（n=96）来自中国12个省的26个畜群，而NAS（n=112）来自中国18个省的59个畜群。用16srrna部分测序法在物种水平上鉴定NAS，而用随机扩增多态DNA（RAPD）PCR法测定分离株的遗传关系。最后，用PCR方法检测抗性基因和生物膜形成基因。产色葡萄球菌（33%）是最常见的NAS，其次是sciuri葡萄球菌（17%）和表皮葡萄球菌（8%）。金黄色葡萄球菌分为12种基因型，其中2种占56%。显色葡萄球菌（n=37）共分为8个RAPD型，其中2个流行型占73%。金黄色葡萄球菌中最常见的ARG是blaZ（95%），其次是tetM（33%）、tetK（31%）、ermT（26%）和aacA-aphD（23%）。mecA和vanA的检出率分别为16%和4%。在NAS中，blaZ（100%）、mecA（73%）、tetK（79%）、tetM（96%）、mphC（63%）和msrA（54%）被频繁检测到。抗微生物基因mecA、tetK、tetL、tetM、dfrG、ermB、msrA、mphC、aadD和aphA3在NAS中的检出率高于金黄色葡萄球菌。从牛临床乳腺炎分离的葡萄球菌中经常检测到生物膜形成基因（icaA和icaD）。中国奶牛场金黄色葡萄球菌和显色葡萄球菌的RAPD分析表明，特定的基因型已在牛群中传播，并对乳房的适应性增强。ARG的高流行率，特别是在NAS中，突出了选择多药耐药葡萄球菌作为ARG储备库的风险。

        Staphylococcus species, categorized into Staphylococcus aureus and non-aureus staphylococci (NAS), are frequent causes of mastitis in dairy cattle around the world. Current treatments using antimicrobials are under increasing scrutiny due to rising prevalence of multi-drug resistance in S. aureus. Objectives of this study were to determine: (1) genetic diversity of Staphylococcus species isolated from clinical mastitis in cows from large Chinese dairy farms; and (2) prevalence and distribution of antimicrobial resistance genes (ARG) in these isolates. Staphylococcus aureus (n = 96) were isolated from 26 herds located in 12 provinces of China, whereas NAS (n = 112) were isolated from 59 herds located in 18 provinces of China. The NAS were identified at the species level using a partial 16S rRNA sequencing method, whereas random amplification of polymorphic DNA (RAPD) PCR was done to determine genetic relationships of isolates. Finally, PCR was used to detect resistance and biofilm formation genes. Staphylococcus chromogenes (33%) was the most common NAS species, followed by Staphylococcus sciuri (17%) and Staphylococcus epidermidis (8%). Staphylococcus aureus was grouped in 12 genotypes, of which 2 types represented 56% of isolates. Staphylococcus chromogenes (n = 37) clustered into 8 RAPD types, with 2 prevalent types containing 73% of isolates. The most prevalent ARG in S. aureus isolates was blaZ (95%), followed by tetM (33%), tetK (31%), ermT (26%), and aacA-aphD (23%). The mecA and vanA were detected in 16 and 4% of isolates, respectively. In NAS, blaZ (100%), mecA (73%), tetK (79%), tetM (96%), mphC (63%), and msrA (54%) were frequently detected. Antimicrobial resistance genes mecA, tetK, tetL, tetM, dfrG, ermB, msrA, mphC, aadD, and aphA3 were more commonly detected in NAS than in S. aureus. Biofilm formation genes (icaA and icaD) were frequently detected in staphylococci isolated from bovine clinical mastitis. The existence of predominant RAPD types in S. aureus and S. chromogenes isolates across Chinese dairy farms indicated that specific genotypes had disseminated within herds and become more udder-adapted. High prevalence of ARG, especially in NAS, highlighted the risk of selection of multi-drug resistant staphylococci with potential as a reservoir of ARG.

        https://www.journalofdairyscience.org/article/S0022-0302(18)31149-4/fulltext