Aeromonas spp. are members of the Vibrionaceae (Janda, 1991). Although they are common in fresh surface water, their presence in faeces of several animals and humans has been proved (Boynukara et al., 2002; Jindal et al., 1993). Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of whole-cell proteins have been used for typing several bacterial species, including Aeromonads (Stephenson and Tabaqchali 1986; Stephenson et al., 1987). A more sensible approach might be to identify isolates as A. hydrophila, A. sobria or A. caviae, and use an electrophoretic fingerprinting technique to further characterize them (Popoff, 1984), Maclnnes et al. (1979) did the first DNA hybridization experiments with Aeromonas, and concluded that the genus consist of two main evolutionary lines; a diverse group of motile Aeromonads and genetically more homogeneous non-motile Aeromonads. Fanning et al. (1985) confirmed that all strains of Aeromonas were more closely related to each other than to species in other families, and found that motile Aeromonas species could be divided into at least 10 different DNA hybridization.