Human isolates of Aeromonas possess Shiga toxin genes (stx1 and stx2) highly similar to the most virulent gene variants of Escherichia coli.

Strains producing Shiga toxins, encoded by stx1 and stx2 genes, can cause diarrhoea, haemorrhagic colitis and haemolytic uremic syndrome. PCR screening of 80 clinical Aeromonas strains showed that 19 were stx1-positive and only one was positive for both stx1 and stx2. PCR bands were very faint for some strains and negative results were obtained after subculturing. The obtained sequences of Aeromonas stx1 and stx2 genes were highly similar to those of the most virulent stx gene variants of Shiga toxin-producing Escherichia coli. These results may lead to a better understanding of the potential pathogenicity and virulence mechanisms of Aeromonas.