A total of 40 isolates of Aeromonas inclusive 12 from cases of diarrhea and 28 from water samples comprising 24 A. hydrophila, 10 A. sobria and 6 A. caviae were subjected to analysis of their biochemical characteristics and virulence factors. Fermentation of mannitol, lactose and indole was observed in all the 14 species of A. hydrophila recovered from water samples. All the 2 clinical isolates of A. sobria tested fermented mannitol and lactose. Among the virulence factors tested, 57.54% of the environmental isolates produced b-hemolysin, while higher 66.66% of the clinical isolates produced b-hemolysin. There was significant difference between clinical (92.85%) and environmental (66.66%) isolates of Aeromonas with respect to their enterotoxigenicity in suckling mice in-vivo. The result suggests that all the haemolytic environmental isolates could be enteropathogenic. From this study, we were able to delineate the difference between clinical and environmental isolates of the Nigerian strains of Aeromonas with respect to their biochemical characteristics, virulence factors and enterotoxigenicity. Further studies involving serogrouping, cytotoxic studies and molecular typing of aeromonads in Nigeria is necessary to reveal other virulent factors involved in diarrhoea.
Biochemical characteristics, clinical and environmental Virulence factors
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