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The distribution and phenotypic activity of the genes encoding for serine protease, glycerophospholipid-cholesterol acyltransferase, lipases, aerolysin/hemolysin and DNases were investigated in 234 isolates identified by 16S rDNA-RFLP representing all the species of Aeromonas. The former three genes were found to be highly conserved among the genus. Aerolysin/hemolysin and DNase genes and β-hemolytic activity were significantly more frequent in clinical than in environmental isolates. Aerolysin/hemolysin and serine protease genes were present in all β-hemolytic strains supporting serine protease as possibly important for the activation of the former gene. The high prevalence of virulence factors in clinical isolates indicates that they may play a role in the mechanisms of pathogenesis of these microorganisms.

The aim of this study was to investigate the presence of markers of pathogenicity islands that may be informative to detect the virulent PAI carriers of clinical and environmental strains of Aeromonasspp. isolated in Mexico. virB2, virB9and virB11genes were found in Aeromonasstrains isolated from environmental and clinical sources while cagEand tfc16genes were only in strains of environmental origin. Having performed the wide screening presented in this study, we now have a set of strains to map and confirm the presence of a pathogenicity island in Aeromonasstrains isolated in Mexico.