Biological characteristics of enteropathogenic Aeromonas species isolated from different Egyptian foods

A total of 185 food samples in Sharkia Governorate, Egypt were analyzed for the presence of Aeromonas spp. The recovered isolates were characterized by biochemical tests based on Bergey's Manual of Systematic Bacteriology and confirmed by API-20E kit. Of the samples analyzed, 56 (30.27 %) were positive for Aeromonas spp., with the highest incidence in raw milk (55 %) followed by Nile tilapia (48.6 %). A. hydrophila and A. salmonicida were the most predominantly isolated from raw milk and A. caviae was the most prevalent in raw lean beef. A variety of extracellular virulence factors were determined and 83.3 % exhibited beta-hemolytic activity; 80 % exhibited lecithinase activity; 75 % exhibited protease activity and 90 % exhibited lipolytic activity. Furthermore, the cytotoxic (act) and the cytotonic (alt) enterotoxins were screened in three selected isolates using PCR assay and the data showed the detection of the two genes with predicted sizes of 232 bp and 442 bp fragments, respectively. These findings indicated a major health risk of infection with enterotoxigenic Aeromonas bacteria for people consuming raw and improper cooked food in Egypt.