Pathogenic infection and microbial composition of yellow catfish (Pelteobagrus fulvidraco) challenged by Aeromonas veronii and Proteus mirabilis

The catfishes are a group of economically important freshwater fish in China, which in recent years have suffered heavy losses as a result of bacterial outbreaks. In this study, we examined the diversity of the microbiome of infected skin mucus of yellow catfish (Pelteobagrus fulvidraco) and channel catfish (Ictalurus punctatus) and analyzed the bacterial pathogens. We found several common pathogenic bacteria, such as Aeromonas spp., Vibrio spp., Moraxella spp. and Proteus spp. present in both fish species, but with significantly different bacterial community structures. We isolated and cultured Aeromonas veronii and Proteus mirabilis and validated their infectivity in zebrafish (Danio rerio) and yellow catfish. Intraperitoneal injection of either bacteria into zebrafish, but not immersion, caused 100% mortality and ovary fragmentation. Yellow catfish was more sensitive than zebrafish with 100% mortality in the immersion challenges with A. veronii or P. mirabilis, and with a higher abundance of A. veronii in the P. mirabilis-challenged group compared to control. To our knowledge, this is the first study on the pathogenicity of P. mirabilis in yellow catfish, and the results will help to develop effective strategies for the disease prevention and control in catfish farming.