Enteropathogenicity of Aeromonas jandaei and A. trota

An experimental study of five isolates of Aeromonas jandaei and 12 of A. trota was carried out to examine if they produced an enterotoxic substance, and if so, to characterise that factor and to see if it caused any mucosal damage. Only two of the A. trota strains caused fluid accumulation in the initial rabbit ileal loop (RIL) tests. The remaining strains did so only after one to five sequential passages through RILs and once they caused a secretory response they showed a gradual enhancement of fluid outpouring after each subsequent passage. Inocula of ~1×105 viable cells and 0.25 ml of culture filtrate caused fluid accumulations comparable to those of toxigenic V. cholerae 569B. The enterotoxic factors of both organisms were inactivated when held at 56°C for 20 min or 65°C for 10 min and showed biological activity over a wide range of pH. The only histopathological change observed in the ileal loop was depletion of mucus from the goblet cells. These data thus indicate that strains of A. jandaei and A. trota may produce a heat-labile and pH-stable diarrhoeagenic substance that causes little or no damage to the intestinal mucosa, like that of other known heat-labile enterotoxins