Veterinary and Agrochemical Research Center, CODA-CERVA-VAR, Groeselenberg 99, B-1180 Ukkel, Belgium.
Vet Microbiol. 2010 Jul 29;144(1-2):166-71. doi: 10.1016/j.vetmic.2009.12.044. Epub 2010 Jan 11.
Methicillin-resistant Staphylococcus aureus (MRSA) is infrequently reported in mastitis. Yet, as in many other countries, the prevalence of methicillin resistance among S. aureus from mastitis is currently unknown in Belgium. To elucidate this, the presence of mecA was investigated in 118 S. aureus strains originating from diagnostic mastitis milk samples from 118 different farms experiencing S. aureus mastitis. MRSA strains were characterized by disk diffusion susceptibility testing, spa-typing, MLST and SCCmec-typing. In an additional study, four MRSA-positive farms were selected to assess the in-herd prevalence of MRSA, by sampling all cows in lactation. Isolated MRSA strains were similarly characterized. The mecA gene was detected in 11 (9.3%) of the 118 S. aureus isolates, indicating that nearly 10% of the Belgian farms suffering from S. aureus mastitis have an MRSA problem. The in-herd prevalence varied between 0% and 7.4%. Characterization of the MRSA strains showed that they were all resistant to tetracycline. Additional resistances to macrolides, lincosamides and aminoglycosides were frequently detected. The strains were ST398, spa-types t011 or t567 and had SCCmec-type IVa or V, proving that they belong to the emerging livestock-associated MRSA (LA-MRSA) strains of CC398. Our study shows that after detection in Belgian pigs, horses and poultry, LA-MRSA has also attained Belgian cattle. It is the first report on frequent isolation of LA-MRSA from bovine infections. As the in-herd isolation rate resembles that of regular S. aureus in farms experiencing S. aureus mastitis, the multi-resistance of LA-MRSA strains may cause future treatment problems.
耐甲氧西林金黄色葡萄球菌（MRSA）在乳腺炎中报道较少。然而，与许多其他国家一样，目前尚不清楚比利时乳腺炎中金黄色葡萄球菌的耐甲氧西林率。为了阐明这一点，研究了来自 118 个不同发生金黄色葡萄球菌乳腺炎的农场的诊断性乳腺炎奶样中 118 株金黄色葡萄球菌菌株中 mecA 的存在。通过纸片扩散药敏试验、spa 型、MLST 和 SCCmec 型对 MRSA 菌株进行了特征描述。在一项额外的研究中，选择了四个 MRSA 阳性农场，通过对所有泌乳奶牛进行采样来评估 MRSA 的 herd 内流行率。同样对分离的 MRSA 菌株进行了特征描述。在 118 株金黄色葡萄球菌分离株中检测到 mecA 基因 11 株（9.3%），表明近 10%的比利时农场遭受金黄色葡萄球菌乳腺炎的农场存在 MRSA 问题。 herd 内流行率在 0%至 7.4%之间变化。MRSA 菌株的特征表明它们均对四环素耐药。还经常检测到对大环内酯类、林可酰胺类和氨基糖苷类的耐药性。这些菌株均为 ST398、spa 型 t011 或 t567，且 SCCmec 型为 IVa 或 V，证明它们属于新兴的畜群相关耐甲氧西林金黄色葡萄球菌（LA-MRSA）菌株 CC398。我们的研究表明，在比利时猪、马和家禽中检出后，LA-MRSA 也已进入比利时牛群。这是首次报告从牛感染中频繁分离出 LA-MRSA。由于 herd 内分离率类似于经历金黄色葡萄球菌乳腺炎的农场中常规金黄色葡萄球菌的分离率，因此 LA-MRSA 菌株的多重耐药性可能会导致未来的治疗问题。
