Screening and characterisation of antagonistic Pseudomonas aeruginosa FARP72 as a potential probiotic agent

Abstract

A search for antagonistic bacteria from the skin mucus of Indian major carps and freshwater catfish was attempted. A total of 41 potent antagonistic bacterial strains were isolated, purified and identified from 25 fish samples, of which 82.93% (n=34) were Gram positive and 17.07% (n=7) were Gram-negative bacteria. Antagonistic activity of these bacteria were confirmed against pathogenic human and fish bacteria viz., Aeromonas hydrophila, Bacillus subtilis, Bacillus amyloliquefaciens, Escherichia coli, Edwardsiella tarda, Klebsiella pneumoniae, Enterohaemorrhagic Escherichia coli (EHEC), Pseudomonas aeruginosa, Salmonella typhi, beta haemolytic Streptococcus, Staphylococcus aureus ATCC12598 and Vibrio cholerae. Among all the bacterial strains tested, broad spectrum of inhibitory activity was elucidated by Pseudomonas aeruginosa FARP72, isolated from Clarias batrachus. Species identity of the antagonistic bacterial strain P. aeruginosa FARP72 was confirmed using molecular technique (16S rDNA analysis) and also by analysis of fatty acid methyl esters (FAME analysis). The antagonistic bacterium P. aeruginosa FARP72 has fulfilled majority of the pre-requisite features for a bacterial strain to be used as probiotic. The strain was also proved to be non-pathogenic. Results suggest that P. aeruginosa FARP72 can be a substitute to the commercially available and indiscriminately used common antibiotics used in aquaculture.