Streptococcosis is a bacterial disease in tilapia that produces economic losses, caused mainly by Streptococcus agalactiae and S. iniae. It is treated using oxytetracycline and florfenicol, which when inappropriately used promotes the selection of antibiotic resistance genes (ARGs). The disease has been mainly associated with stress events such as variations in temperature. The aims of the present study were (1) to detect by molecular methods two species of Streptococcus sp. in a tilapia farm, (2) to relate their presence to physicochemical parameters in the culture system, and (3) to detect the presence of ARGs in tilapia tissues and/or ponds. Tilapia grow-out ponds (n = 30) were sampled, collecting 15 individuals per pond. The physicochemical parameters of water were measured in each pond. Per pond, organs such as the liver, spleen, brain, and eyes were collected from each individual. Then, each organ type was pooled with the respective organ of the other individuals, processed for DNA extraction, and used for PCR analyses to determine the presence of S. agalactiae and S. iniae and for the detection of ARGs (tetM, tetO, fexA, and ermB). The correlations between the presence of S. agalactiae and water physicochemical parameters were determined. Sixty percent of the ponds and 46% of the organ pools were positive for S. agalactiae, whereas S. iniae was not detected. The positive samples showed the following resistance genes: tet(O) (29.1%), tet(M) (12.7%), and erm(B) (1.8%). A moderate but significant positive correlation was found between temperature and the presence of S. agalactiae. This work reported the molecular detection of two species of Streptococcus and ARGs, providing information that allows fast and effective control of these pathogens in tilapia farming. In addition, a future complementary study on Streptococcus sp. serotype distribution and antibiotic resistance genes from tilapia cultured in Costa Rica could also contribute to increase the knowledge of S. agalactiae infections in tilapia farming worldwide.

链球菌病是罗非鱼的一种细菌性疾病，会造成经济损失，主要由无乳链球菌和犬链球菌引起。它使用土霉素和氟苯尼考进行治疗，如果使用不当，会促进抗生素抗性基因 (ARG) 的选择。该疾病主要与压力事件有关，例如温度变化。本研究的目的是（1）通过分子方法检测两种链球菌属。在罗非鱼养殖场中，(2) 将它们的存在与养殖系统中的理化参数联系起来，以及 (3) 检测罗非鱼组织和/或池塘中 ARG 的存在。罗非鱼养成池 ( n= 30) 个样本，每个池塘收集 15 个个体。在每个池塘中测量水的理化参数。每个池塘收集每个个体的器官，如肝脏、脾脏、大脑和眼睛。然后，将每种器官类型与其他个体的相应器官合并，进行 DNA 提取处理，并用于 PCR 分析以确定无乳链球菌和犬链球菌的存在以及检测 ARG（tet M、tet O , fex A 和erm B)。确定了无乳链球菌的存在与水物理化学参数之间的相关性。60% 的池塘和 46% 的器官池对S. agalactiae，而未检测到S. inia e 。阳性样本显示以下抗性基因：tet (O) (29.1%)、tet (M) (12.7%) 和erm (B) (1.8%)。在温度和无乳链球菌的存在之间发现了中等但显着的正相关。这项工作报告了两种链球菌和 ARG的分子检测，提供了可以在罗非鱼养殖中快速有效控制这些病原体的信息。此外，未来对链球菌的补充研究sp. 来自哥斯达黎加养殖的罗非鱼的血清型分布和抗生素抗性基因也有助于增加对全球罗非鱼养殖中无乳链球菌感染的了解。