Biochemical and molecular genetic identification of the bacterial pathogen - Aeromonas bestiarum from a diseased Siberian sturgeon (Acipenser baerii)

The article presents the results of isolation and identification of the bacterium Aeromonas bestiarum from diseased individuals of Siberian sturgeon (Acipenser baerii) reared in recirculating aquaculture system (RAS). As a result of biochemical studies, the isolated strain A. bestiarum AB002 is characterized as: a Gram-negative, non-motile oxidase-positive bacillus capable of growing in a wide temperature range from 13 to 42 ºC. In addition, strain AB002 is characterized by the hydrolysis of gelatin and esculin, forming H2S and indole, and exhibits arginine dihydrolase activity. The analysis of bacterial resistance to antibiotics revealed that strain AB002 is resistant to multiple groups of antibiotics, including Penicillins (Oxacillin, Penicillin G, Ampicillin, Amoxicillin); Cephalosporins (Cefazolin); Macrolides (Erythromycin); Lincomycins (Lincomycin); Rifamycins (Rifampicin); Coumarins (Novobiocin). The analysis of virulence factors revealed that the pathogenic strain A. bestiarum AB002 is characterized by the presence of 6 virulence genes out of 10 studied, among which lipase (pla), cytotonic enterotoxin (alt), serine protease (ahe2), DNAase (nucl), cholesterol acyltransferase (gcaT), aerolysin (aerA) were identified.