Antibiotic susceptibility pattern of bacteria isolated from freshwater ornamental fish, guppy showing bacterial disease

Antimicrobial resistance is one of the major threats faced in aquaculture systems. Hence the present study is mainly focused on to determine the antimicrobial susceptibility associated with pathogens derived from diseased freshwater ornamental guppy fishes. Around fifteen isolates were resolved from the infected fishes and subjected to antimicrobial susceptibility testing, phenotypic and genotypic characterization. Disc diffusion method was adopted for checking the antibiotic susceptibility using 17 antibiotic discs belonging to different classes. Dendrogram generated 5 clusters based on the biochemical tests and representative isolates were sequenced and identified as Aeromonas hydrophila, Aeromonas sobria, Pseudomonas putida, Acinetobacter soli and Kurthia gibsonii. The Shannon wiener diversity index of the resolved isolates was found to be 1.395 as determined by Primer-E software. Among the isolates, the majority of them was found to be Pseudomonas putida and exhibited higher antibiotic resistance towards antibiotics of 10 classes including third generation Cephalosporin and others showed the same against antibiotics of at least 5 classes tested. All of the recovered isolates possessed the MAR index of greater than 0.2, indicating the heavier dose of antibiotics in the farm. The detection of plasmid-mediated class I integron in Aeromonas hydrophila, Aeromonas sobria and Acinetobacter soli indicated the possibility of heavier dissemination of antimicrobial resistant genes among the ornamental fishes. Gentamycin and Ciprofloxacin were significantly effective against all the isolates and can be successfully applied in aquaculture. The occurrence of antibiotic resistance reminds the proper surveillance and continuous monitoring programmes in the fish farms and usage of other effective alternatives.