Isolation of Probiotic Bacteria from Macrobrachium rosenbergii and Their Antagonistic Efficacy against Pathogenic Bacteria

The probiotic bacteria isolated from prawn, Macrobrachium rosenbergii was studied for their morphological and biochemical characteristics as well as their antagonistic efficacy against pathogenic bacteria. A total of three probiotic bacteria viz. White Colour Bacteria (WCB), Red Colour Bacteria (RCB) and Yellow Colour Bacteria (YCB) were isolated from intestine of healthy prawn while three pathogenic bacteria viz. PB1, PB2 and PB3 were isolated from infected antennae and muscles of moribund prawn. Depending on their physical and biochemical features, the probiotic isolates were gram-positive, rod shaped and motile bacteria belonging to Bacillus spp. and the pathogenic bacteria were also identified as gram-negative, cocci shaped and motile bacteria fit in Enterococcus spp., Vibrio spp. and Micrococcus spp. The optimum culture conditions of all isolates were at pH 7.0 and 37°C temperature. Results on the antibiogram profile of pathogenic bacteria revealed that majority of the isolates were sensitive (43.58%) or intermediate (30.76%) against thirteen antibiotics. The probiotic bacterial antagonistic activities were tested against Enterococcus, Vibrio and Micrococcus spp.by cross-streak method. The results indicate that the strain of YCB showed inhibitory effects against Enterococcus spp. (5 mm), Vibrio spp. (5 mm) and Micrococcus spp. (3 mm). Similarly, WCB showed inhibitory effects against Enterococcus spp. (4 mm), Vibrio spp. (3 mm) and Micrococcus spp. (4 mm). RCB strains showed inhibition against Micrococcus spp. (3 mm) only, but not against Enterococcus spp. and Vibrio spp. Based on the results, it can be concluded that the isolated probiotic bacteria could be a good candidate to consider for further studies to control the pathogenic bacteria in prawn culture.