Departamento de Higiene Veterinária e Saúde Pública, Faculdade de Medicina Veterinária e Zootecnia (FMVZ), Universidade Estadual Paulista (UNESP), Campus de Botucatu, Distrito de Rubião Júnior, s/n 18618-970 Botucatu, SP, Brazil.
Res Vet Sci. 2012 Aug;93(1):34-8. doi: 10.1016/j.rvsc.2011.07.016. Epub 2011 Sep 8.
Mastitis is the most common infectious disease affecting dairy cattle; in addition, it remains the most economically important disease of dairy industries around the world. Streptococcus agalactiae, a contagious pathogen associated with subclinical mastitis, is highly infectious. This bacterium can cause an increase in bulk tank bacterial counts (BTBC) and bulk tank somatic cell counts (BTSCC). The microbiological identification of S. agalactiae in samples from bulk tanks is an auxiliary method to control contagious mastitis. Thus, there are some limitations for time-consuming cultures or identification methods and additional concerns about the conservation and transport of samples. Bulk tank samples from 247 dairy farms were cultured and compared through polymerase chain reaction (PCR), directed to 16S rRNA genes of S. agalactiae, followed by BTBC and S. agalactiae isolation. The mean value of BTBC was 1.08×10(6) CFU mL(-1) and the bacterium was identified through the microbiological method in 98 (39.7%; CI(95%)=33.8-45.9%) and through PCR in 110 (44.5%; CI(95%)=38.5-50.8%) samples. Results indicated sensitivity of 0.8571±0.0353 (CI(95%)=0.7719-0.9196) and specificity of 0.8255±0.0311 (CI(95%)=0.7549-0.8827). The lack of significant difference between microbiological and molecular results (κ=0.6686±0.0477 and CI(95%)=0.5752-0.7620) indicated substantial agreement between the methods. This suggests that PCR can be used for bulk tank samples to detect contagious mastitis caused by S. agalactiae.
乳腺炎是影响奶牛最常见的传染病；此外，它仍然是全世界奶牛业最重要的经济疾病。无乳链球菌是一种与隐性乳腺炎相关的传染性病原体，具有高度传染性。这种细菌会导致大容量罐细菌计数（BTBC）和大容量罐体细胞计数（BTSCC）增加。大容量罐样品中无乳链球菌的微生物学鉴定是控制传染性乳腺炎的辅助方法。因此，对于耗时的培养或鉴定方法存在一些限制，并且对样品的保存和运输也存在一些担忧。对 247 个奶牛场的大容量罐样品进行培养，并通过聚合酶链反应（PCR）进行比较，该方法针对无乳链球菌的 16S rRNA 基因，然后进行 BTBC 和无乳链球菌分离。BTBC 的平均值为 1.08×10(6)CFU mL(-1)，通过微生物学方法在 98 份（39.7%；95%置信区间[CI]（33.8-45.9%））和 110 份（44.5%；CI（38.5-50.8%））样品中鉴定出该细菌。结果表明，敏感性为 0.8571±0.0353（95%CI（0.7719-0.9196）），特异性为 0.8255±0.0311（95%CI（0.7549-0.8827））。微生物学和分子结果之间无显著差异（κ=0.6686±0.0477，95%CI（0.5752-0.7620））表明两种方法具有高度一致性。这表明 PCR 可用于大容量罐样品，以检测由无乳链球菌引起的传染性乳腺炎。
