Gerez Gabriela, Hernandez Luciana Belén, Cadona Jimena, Sanso Andrea Mariel, Bustamante Ana Victoria
Laboratorio de Inmunoquímica y Biotecnología, Centro de Investigación Veterinaria de Tandil (CIVETAN), CONICET, CIC, Facultad de Ciencias Veterinarias, UNCPBA, 7000, Tandil, Buenos Aires, Argentina.
BMC Vet Res. 2025 May 13;21(1):338. doi: 10.1186/s12917-025-04584-4.
Bovine mastitis is an important health problem in dairy cattle which affects the quality and yield of milk and causes significant economic losses in the dairy industry. Streptococcus agalactiae is a Gram-positive and zoonotic bacterium that causes clinical and subclinical contagious bovine mastitis. The main strategy for the control of this pathogen in dairy herds is the antimicrobial therapy. The aim of this study was to determine the genetic diversity of S. agalactiae using Multiple Locus Variable number tandem repeat -VNTR- Analysis (MLVA), serotypes, virulence factors (VF) and antimicrobial resistance (AMR) profiles and to compare the discrimination power of these different methods in strains isolated from cattle with mastitis in Argentinian dairy farms.
Eighty-seven S. agalactiae isolates obtained from dairy cattle with mastitis in Argentina were analyzed. The detected serotypes were III, II and Ia. The most frequent virulence and AMR detected genes were cpsA, hylB, PI-2b, cylE, rib, spb1, and tetO and ermB respectively. A total of 36 VF + AMR profiles were detected with a discriminatory power of the method of Ds = 0.96. The MLVA based on six VNTRs showed 29 profiles with a Ds = 0.90. The analysis of VF + AMR + MLVA data together showed 59 profiles with an increased discriminatory power (Ds = 0.98).
This study highlights that the MLVA is recommended to add to other methodologies in order to study epidemiological relationships in this species Although within each dairy farm there was a predominance of certain serotypes/virulence profiles, the characteristics did not show total homogeneity, as expected due to the contagious nature of the pathogen. This suggests the incorporation of animals from other herds at some point, a practice not uncommon among dairy farms in Argentina. By other hand, the detection of a same clone in the same farm in different periods confirms that S. agalactiae strains can persist on dairy farms for a long time.
牛乳腺炎是奶牛养殖中的一个重要健康问题，它会影响牛奶的质量和产量，并给乳制品行业造成重大经济损失。无乳链球菌是一种革兰氏阳性人畜共患病细菌，可引起临床和亚临床传染性牛乳腺炎。控制奶牛群中这种病原体的主要策略是抗菌治疗。本研究的目的是使用多位点可变数目串联重复序列分析（MLVA）、血清型、毒力因子（VF）和抗菌药物耐药性（AMR）谱来确定无乳链球菌的遗传多样性，并比较这些不同方法对阿根廷奶牛场乳腺炎病牛分离株的鉴别能力。
对从阿根廷患有乳腺炎的奶牛中获得的87株无乳链球菌分离株进行了分析。检测到的血清型为III、II和Ia。检测到的最常见的毒力和AMR基因分别是cpsA、hylB、PI - 2b、cylE、rib、spb1以及tetO和ermB。共检测到36种VF + AMR谱，该方法的鉴别力Ds = 0.96。基于6个VNTR的MLVA显示有29种谱，Ds = 0.90。将VF + AMR + MLVA数据一起分析显示有59种谱，鉴别力增强（Ds = 0.98）。
本研究强调，为了研究该物种的流行病学关系，建议将MLVA添加到其他方法中。尽管在每个奶牛场中某些血清型/毒力谱占主导，但由于病原体的传染性，这些特征并未显示出完全的同质性。这表明在某个时候引入了其他牛群的动物，这种做法在阿根廷的奶牛场中并不少见。另一方面，在同一农场不同时期检测到相同的克隆，证实无乳链球菌菌株可在奶牛场长期存在。
