Cytotoxin testing of environmental Aeromonas spp. in Vero cell culture.

BACKGROUND & OBJECTIVES: Aeromonas spp. are known to cause a variety of infections in humans and this organism has been isolated from a variety of sources including environmental sources. The pathogenicity of the environmental isolates in and around Vellore has not been studied. This study was conducted to determine the cytotoxicity of the Aeromonas spp. isolated from water bodies, soil sediments, plankton and sewers in and around Vellore. METHODS: Aeromonas spp. isolated from environmental sources were identified by standard procedures. Representative isolates of Aeromonas spp. were tested for cell free cytotoxic factor in tissue culture system. Undiluted and diluted cell free filtrates of isolates and known toxigenic and non-toxigenic bacteria were added to Vero cell monolayer in microtitre plates. After appropriate incubation in 5 per cent CO2 atmosphere, the microtitre plate was examined for cytopathic effect. Cell detachment and shrinkage of Vero cells were recorded as toxic changes. RESULTS: All 36 environmental isolates demonstrated cytopathic effect of which 41.7, 50 and 8.3 per cent belonged to A. hydrophila, A. veronii biotype sobria and A. caviae respectively. INTERPRETATION & CONCLUSION: The results demonstrated the presence of potentially pathogenic environmental aeromonads in and around Vellore and they produced cytotoxin.