Attenuated virulence of pigment-producing mutant of Aeromonas veronii bv. sobria in HeLa cells and Nile tilapia (Oreochromis niloticus)

Abstract Aeromonas species are potential water/foodborne pathogens, whereas Aeromonas veronii bv. sobria is one of the most virulent species to human and fish. Most current experimental evidence has publicized that suicide plasmid dependent IS 1- element untargeted integration into A. veronii bv. sobria ATCC 9071T strain was recently used to generate brown pigment-producing and spontaneous pelleting (BP + SP + ) mutant. Current study was conducted to compare virulence of wild-type ATCC 9071T strain and its BP + SP + mutant with respect to cytotoxicity in HeLa cells and lethality in Nile tilapia. It was found that the cytotoxicity of wild-type ATCC 9071T strain to HeLa cells has reached 75% versus 50% for the cytotoxicity of BP + SP + mutant. Further, the median lethal dose (LD 50 ) of wild-type ATCC 9071T strain in Nile tilapia was 8.25 Log 10 colony-forming units (CFU)/ml, compared to 9.16 Log 10  CFU/ml for the LD 50 of BP + SP + mutant. Thus, current study supports the notion that non pigment-producing Aeromonas strains are more virulent than pigment-producing ones.