Phylogenetic identification and distribution of enterotoxin genes in aeromonas strains isolated from Pet Fish

In the present study, 47 strains of Aeromonas sp. were collected from cultured koi (n = 11) and imported pet fish (n = 36). All strains were identified by phylogenetic analysis using partial sequences of the gyrB gene. In addition, PCR assays were used to detect the presence of genes for cytotoxic enterotoxin (act) and cytotonic enterotoxin (alt and ast). In the phylogenetic identification, the strains comprised five species, A. veronii (n = 36), A. hydrophila (n = 7), A. jandaei (n = 1), A. aquariorum (n = 1) and A. allosaccarophila (n = 2). Of the identified species, A. jandaei, A. aquariorum and A. allosaccarophila were earlier unrecorded in microbiological fields of Korea. In the detection of enterotoxin genes, the act, alt and ast genes were respectively presented in 85.1, 61.7 and 17.0% of strains. The act and act/alt gene patterns were prominent among Aeromonas strains, especially A. veronii. On the other hand, only A. hydrophila strains harbored all three of the enterotoxin genes. The results of the present study suggest that pet fish could be a potential risk factor for Aeromonas infection in humans.