Studies on diseases in freshwater prawn, Macrobrachium rosenbergii have been conducted to find out the pathogens associated with disease and their characteristic and antimicrobial sensitivity against different antibiotics. Based on the result of the study a variety of bacteria have been found among which four genera Vibrio, Pseudomonas and Aeromonas are found to be predominant and these are the probable pathogens of Macrobrachium rosenbergii. These bacterial strains are identified based on colony morphology on respective selective media, gram staining and biochemical test. Their in-vitro pathogenicity was studied and all the isolated are found to be pathogen as they showed a strong binding affinity in congo-red plate except Vibrio anguillarum (02) and haemolysed the blood cell except  Pseudomonas anguilliseptica. These strains were examined for their resistance to twenty-two selective antibiotics. All the species are found to highly susceptible to ofloxacin, ciprofloxacin, and erythromycin-15. Vibrio species are found to be resistance to tetracycline and oxytetracycline where as all other strains are found to be susceptible to these antibiotics.