Experimental evidence for enteropathogenicity in Aeromonas veronii

Eleven ornithine-positive strains of Aeromonas (9 A. veronii and 2 provisionally classified as Aeromonas species ornithine positive) were tested for ability to cause fluid accumulation in the rabbit ileal loop. All eight beta-hemolytic strains caused fluid accumulation. Gel diffusion analysis revealed that the A. veronii beta-hemolysin was serologically related to the A. hydrophila beta-hemolysin, a known enterotoxic molecule. The biological activity of the A. veronii hemolysin was neutralized by antiserum to A. hydrophila hemolysin. One of three strains that were not beta-hemolytic caused fluid accumulation but only when the ileal loops were inoculated with live cultures. These results suggest that A. veronii is a potential enteropathogen that can cause diarrhea by means of a cell-freed enterotoxin (beta-hemolysin) or by a second mechanism that requires the presence of whole cells.