Vaneci-Silva Daiane, de Abreu Reis Ferreira Daniel, Oliveira André do Vale, Lima de Sousa Elielma, Gomes Fernando Cardoso, Assane Inácio Mateus, Pilarski Fabiana
São Paulo State University (UNESP), Aquaculture Center of UNESP, Laboratory of Microbiology and Parasitology of Aquatic Organisms, Jaboticabal, São Paulo, 14884-900, Brazil.
Graduate Program in Agricultural and Livestock Microbiology, São Paulo State University (UNESP), School of Agricultural and Veterinarian Sciences, Jaboticabal, São Paulo, 14884-900, Brazil.
Microb Pathog. 2025 Mar;200:107348. doi: 10.1016/j.micpath.2025.107348. Epub 2025 Jan 29.
Lactococcus petauri is an emerging pathogen causing piscine lactococcosis in various aquatic species. This disease has been increasingly reported as a cause of mortality in aquaculture. Due to the indiscriminate use of antimicrobials and to promote viable alternatives for their replacement, bioactive peptides with antimicrobial properties can be explored as tools against bacterial infections. Thus, the objective of this study was to identify the pathogen responsible for a mortality outbreak in cage-cultured Nile tilapia (Oreochromis niloticus), assess its pathogenicity, and evaluate the therapeutic efficacy of a commercial bioactive peptide and florfenicol against L. petauri. The bacterium was isolated from affected Nile tilapia exhibiting external and internal hemorrhages, ocular opacity, anorexia, and ascites. Koch's postulates were fulfilled by inoculating healthy fish with 3.6 × 10 CFU/mL of the bacterium, which induced clinical signs of generalized hemorrhage, ascites, and melanosis. Histopathological analysis revealed severe lesions in the liver, spleen, kidney, intestine, and heart, confirming the pathogen's high virulence in Nile tilapia. To evaluate potential treatments, fish were divided into six groups: G1) inoculated with L. petauri and treated with 15 mg/kg of bioactive peptide via gavage; G2) inoculated and treated with 15 mg/kg of florfenicol via gavage; G3) inoculated and treated with intraperitoneal injection of bioactive peptide (15 mg/kg); G4) inoculated and left untreated; G5) treated with PBS via gavage; and G6) inoculated with PBS. After 30 days, survival rates were G1: 36.85 %, G2: 16.79 %, G3: 26.44 %, and G4: 6.7 %. Significantly higher survival was observed in groups G1, G2, and G3 compared to G4. Moreover, bacterial persistence was only absent in groups G1 and G3. The study demonstrates the effectiveness of the bioactive peptide in treating L. petauri infections and preventing bacterial persistence in Nile tilapia, suggesting it is a viable alternative to traditional antimicrobials.
彼得罗乳酸乳球菌是一种新出现的病原体，可在多种水生物种中引起鱼类乳球菌病。作为水产养殖中导致死亡的一个原因，关于这种疾病的报道越来越多。由于抗菌药物的滥用以及为了推广可行的替代药物，具有抗菌特性的生物活性肽可作为对抗细菌感染的工具进行探索。因此，本研究的目的是确定导致网箱养殖尼罗罗非鱼（Oreochromis niloticus）死亡暴发的病原体，评估其致病性，并评价一种商业生物活性肽和氟苯尼考对彼得罗乳酸乳球菌的治疗效果。该细菌是从受影响的尼罗罗非鱼中分离出来的，这些鱼表现出体表和体内出血、眼球浑浊、厌食和腹水症状。通过给健康鱼接种3.6×10 CFU/mL的该细菌，满足了科赫法则，这引发了全身性出血、腹水和黑色素沉着的临床症状。组织病理学分析显示肝脏、脾脏、肾脏、肠道和心脏有严重病变，证实了该病原体对尼罗罗非鱼具有高毒力。为了评估潜在的治疗方法，将鱼分为六组：G1）接种彼得罗乳酸乳球菌并通过灌胃给予15 mg/kg生物活性肽进行治疗；G2）接种并通过灌胃给予15 mg/kg氟苯尼考进行治疗；G3）接种并通过腹腔注射生物活性肽（15 mg/kg）进行治疗；G4）接种但不治疗；G5）通过灌胃给予PBS进行治疗；G6）接种PBS。30天后，存活率分别为G1：36.85%，G2：16.79%，G3：26.44%，G4：6.7%。与G4组相比，G1、G2和G3组的存活率显著更高。此外，仅G1和G3组不存在细菌持续存在的情况。该研究证明了生物活性肽在治疗彼得罗乳酸乳球菌感染和预防尼罗罗非鱼中细菌持续存在方面的有效性，表明它是传统抗菌药物的一种可行替代物。
