First report of natural co-infections and protein profile of Indian major carp, Labeo rohita

Abstract

Aquaculture is a crucial component of global animal protein production, highlighting its significant role in food security. Bacterial co-infections are common in fish farms and severely impact fish health. The prevalence of Aeromonas and Pseudomonas species has been documented in natural co-infections on rohu farms. Infected fish exhibited prominent ulcerative skin lesions, scale erosion, and tail rot. Molecular analysis revealed that Aeromonas veronii was the most dominant species in infected tissues, followed by A. hydrophila, A. dhakensis, Pseudomonas mosselii, and P. fluorescens. The coinfected fish displayed histopathological changes, such as necrotic gills, lymphocytic infiltration, and tubular necrosis in the liver and kidney. Antibiotic susceptibility profiling using nine antibiotic discs indicated the highest sensitivity to oxytetracycline, whereas ampicillin, methicillin, and penicillin exhibited complete resistance across all tissue-associated bacterial isolates. Label-free proteomic analysis of the kidney showed pathogenicity mechanisms related to metabolic pathways, ion binding, oxidoreductase activity and the cellular response to stress in the kidneys of coinfected rohu. Notably, proteins involved in apoptosis, inflammation, and reactive oxygen species (ROS) regulation were upregulated, suggesting their roles in the host response to coinfection. This study specifies for the first time that coinfection on rohu farms is capable of causing pathological changes in the kidney, liver, and gill. The identification of novel host-response proteins may facilitate the development of therapeutic targets and strategies to increase disease resistance and climate resilience in aquaculture.