Li Longping, Zhou Luoxiong, Wang Lihong, Xue Huping, Zhao Xin
College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, People's Republic of China.
College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, People's Republic of China; Department of Animal Science, McGill University, 21,111 Lakeshore, Ste. Anne de Bellevue, Quebec, H9X 3V9, Canada.
PLoS One. 2015 Mar 10;10(3):e0116699. doi: 10.1371/journal.pone.0116699. eCollection 2015.
Emergence of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative staphylococci (MR-CoNS) in bovine milk is a major public health concern. The primary purpose of this research was to determine molecular genetic characteristics and antibiotic resistance of staphylococcal isolates recovered from milk of mastitic cows in the Shaanxi Province in Northwestern China. One hundred and thirteen methicillin-susceptible Staphylococcus aureus (MSSA), one mecA-positive and phenotype-positive MRSA, seven mecA- and mecC- negative but phenotype-positive MRSA and two MR-CoNS including one oxacillin-susceptible mecA-positive Staphylococcus haemolyticus (OS-MRSH) and one mecA-positive and methicillin-resistant Staphylococcus epidermidis (MRSE) isolates were recovered from 214 quarter milk samples on 4 dairy farms. All above 123 isolates were subjected to antibiotic resistance profiling. S. aureus isolates were also genotyped using the spa typing and the multilocus sequence typing (MLST). Eight MRSA and 2 MR-CoNS isolates were additionally tested for SCCmec types. Resistance was common among isolates against ampicillin or penicillin (80.5%), kanamycin (68.3%), gentamicin (67.5%), tetracycline (43.9%) and chloramphenicol (30.1%). However, no isolate was resistant to vancomycin or teicoplanin. Twenty, 29 and 58 isolates showed resistance to 1, 2 or more than 2 antibiotics, respectively. The predominant multidrug resistance profile was penicillin/ampicillin/kanamycin/gentamicin/tetracycline (46 isolates). Most S. aureus isolates belonged to spa types t524 (n = 63), t11772 (a new type, n = 31) and t4207 (n = 15). At the same time, MLST types ST71 (n = 67) and ST2738 (a new type, n = 45) were identified as dominant sequence types. The mecA-positive and phenotype-positive MRSA isolate had a composite genotype t524-ST71-SCCmecIVa, while 7 mecA-negative but phenotype-positive MRSA isolates were all t524-ST71. The OS-MRSH isolate contained a type V SCCmec cassette, while the MRSE isolate possessed a non-typeable SCCmec. The spa-MLST types t11772-ST2738 (n = 27), t11807-ST2683 (n = 4) and t11771-ST2738 (n = 3) were newly identified genotypes of S. aureus. These new genotypes and multidrug-resistant staphylococci could pose additional threat to animal and human health.
牛乳中耐甲氧西林金黄色葡萄球菌（MRSA）和耐甲氧西林凝固酶阴性葡萄球菌（MR-CoNS）的出现是一个重大的公共卫生问题。本研究的主要目的是确定从中国西北陕西省患乳房炎奶牛的乳汁中分离出的葡萄球菌菌株的分子遗传特征和抗生素耐药性。从4个奶牛场的214份乳区乳样中分离出113株甲氧西林敏感金黄色葡萄球菌（MSSA）、1株mecA阳性且表型阳性的MRSA、7株mecA和mecC阴性但表型阳性的MRSA以及2株MR-CoNS，其中包括1株对苯唑西林敏感的mecA阳性溶血葡萄球菌（OS-MRSH）和1株mecA阳性且耐甲氧西林的表皮葡萄球菌（MRSE）。对上述所有123株菌株进行了抗生素耐药性分析。还使用spa分型和多位点序列分型（MLST）对金黄色葡萄球菌菌株进行了基因分型。另外对8株MRSA和2株MR-CoNS菌株进行了SCCmec分型检测。分离菌株对氨苄西林或青霉素（80.5%）、卡那霉素（68.3%）、庆大霉素（67.5%）、四环素（43.9%）和氯霉素（30.1%）耐药很常见。然而，没有分离株对万古霉素或替考拉宁耐药。分别有20、29和58株菌株对1种、2种或2种以上抗生素耐药。主要的多重耐药谱型是青霉素/氨苄西林/卡那霉素/庆大霉素/四环素（46株）。大多数金黄色葡萄球菌菌株属于spa型t524（n = 63）、t11772（一种新型，n = 31）和t4207（n = 15）。同时，MLST型ST71（n = 67）和ST2738（一种新型，n = 45）被确定为优势序列型。mecA阳性且表型阳性的MRSA分离株具有复合基因型t524-ST71-SCCmecIVa，而7株mecA阴性但表型阳性的MRSA分离株均为t524-ST71。OS-MRSH分离株含有V型SCCmec盒，而MRSE分离株具有不可分型的SCCmec。spa-MLST型t11772-ST2738（n = 27）、t11807-ST2683（n = 4）和t11771-ST2738（n = 3）是新鉴定的金黄色葡萄球菌基因型。这些新基因型和多重耐药葡萄球菌可能对动物和人类健康构成额外威胁。
