Garcia Breno Luis Nery, Fidelis Carlos Eduardo, Freu Gustavo, Granja Brunna de Mattos, Dos Santos Marcos Veiga
Qualileite Milk Quality Laboratory, Department of Animal Nutrition and Production, School of Veterinary Medicine and Animal Sciences, University of São Paulo, São Paulo, Brazil.
Front Vet Sci. 2021 Apr 30;8:662201. doi: 10.3389/fvets.2021.662201. eCollection 2021.
The present study aimed to evaluate the diagnostic performance specificity (Sp), sensitivity (Se), positive predictive value (PPV), negative predictive value (NPV), and accuracy (Acc) of two chromogenic culture media for rapid identification of Gram-positive bacteria causing subclinical mastitis (SCM) in dairy cows. For this, the performance of chromogenic culture media Gram-positive (GP) and (Staph) (CHROMagar ™, Paris-France) was evaluated in milk samples collected from: (1) lactating cows with SCM ( = 504), and (2) cows in the post-partum period (PP) (7 ± 3 days post-partum; = 536). Rapid identification of Gram-positive bacteria in chromogenic media was performed by visual inspection of colony colors after 24 h of incubation at 37°C. Bacterial identification by MALDI-TOF mass spectrometry was considered the reference methodology for calculating: Acc, Se, Sp, PPV, NPV, and Cohen's coefficient of agreement (). The chromogenic media GP showed high Acc for identification in both samples of SCM (Se: 89.1%; Sp: 96.3% and Acc: 95.6%) and of cows in PP (Se: 100%; Sp: 99.0% and Acc: 99.1%). Similar results were observed for spp. identification (Se: 90.5%; Sp: 92.5% and Acc: 92.3%) in SCM samples and Se: 100%; Sp: 99.6% and Acc: 99.6% in samples of PP cows using the GP media. However, the GP chromogenic media showed low Se (25.0% in SCM samples and 50.0% in samples of cows in PP) for identification, despite Sp and Acc were high (Sp: 98.3% and Acc: 95.4% in SCM and Sp samples: 99.4% and Acc: 98.9% in PP cow samples). Staph culture media showed high Acc for identification (Se: 80.0%; Sp: 98.8% and Acc: 98.0% in SCM samples and Se: 66.7%; Sp: 100% and Acc: 99.6% in PP cow samples), although the low prevalence of and limit inferences about the performance of identifying these pathogens in Staph media. In conclusion, despite the limitation of the GP media for identification of , GP, and Staph chromogenic media obtained satisfactory diagnostic performance results for the rapid identification of the main Gram-positive pathogens associated with SCM.
本研究旨在评估两种显色培养基对快速鉴定引起奶牛亚临床型乳房炎（SCM）的革兰氏阳性菌的诊断性能，包括特异性（Sp）、敏感性（Se）、阳性预测值（PPV）、阴性预测值（NPV）和准确性（Acc）。为此，对革兰氏阳性显色培养基（GP）和葡萄球菌显色培养基（CHROMagar™，法国巴黎）在采集自以下样本中的性能进行了评估：（1）患有SCM的泌乳奶牛（n = 504），以及（2）产后时期（PP）的奶牛（产后7±3天；n = 536）。通过在37°C孵育24小时后目视检查菌落颜色，对显色培养基中的革兰氏阳性菌进行快速鉴定。将基质辅助激光解吸电离飞行时间质谱（MALDI - TOF MS）进行细菌鉴定视为计算Acc、Se、Sp、PPV、NPV和科恩一致性系数（κ）的参考方法。显色培养基GP在SCM样本（Se：89.1%；Sp：96.3%；Acc：95.6%）和PP期奶牛样本（Se：100%；Sp：99.0%；Acc：99.1%）中对葡萄球菌属的鉴定均显示出高Acc。在SCM样本中使用GP培养基对无乳链球菌鉴定时观察到类似结果（Se：90.5%；Sp：92.5%；Acc：92.3%），在PP期奶牛样本中Se：为100%；Sp：99.6%；Acc：99.6%。然而，GP显色培养基对停乳链球菌鉴定的Se较低（SCM样本中为25.0%，PP期奶牛样本中为50.0%），尽管Sp和Acc较高（SCM样本中Sp：98.3%；Acc：95.4%，PP期奶牛样本中Sp：99.4%；Acc：98.9%）。葡萄球菌显色培养基对金黄色葡萄球菌鉴定显示出高Acc（SCM样本中Se：80.0%；Sp：98.8%；Acc：98.0%，PP期奶牛样本中Se：66.7%；Sp：100%；Acc：99.6%），尽管金黄色葡萄球菌和无乳链球菌的低流行率限制了对葡萄球菌显色培养基中这些病原体鉴定性能的推断。总之，尽管GP培养基在鉴定停乳链球菌方面存在局限性，但GP和葡萄球菌显色培养基在快速鉴定与SCM相关的主要革兰氏阳性病原体方面获得了令人满意的诊断性能结果。
