Production of an enterotoxin by a gastro-enteritis-associated Aeromonas strain

The potential of motile Aeromonas species to cause human gastrointestinal i nfections has been recognised recently. Considerable worldwide epidemiologi cal, microbiological and clinical investigations have shown that some strai ns of the different motile aeromonads are of increasing enteropathogenic si gnificance, especially in children, the elderly and in immunocompromised in dividuals. Some of the diarrhoeal symptoms of Aeromonas-associated gastro-e nteritis have been attributed to enterotoxins. In this study, 15 Aeromonas isolates from clinical and non-clinical sources, representing the three mot ile aeromonads commonly associated with gastro-enteritis (A, caviae, A, hyd rophila and A. veronii biovar sobria), were tested for their ability to cau se fluid accumulation in infant mice by the suckling mouse technique. Eight isolates were found to produce enterotoxin, Of these, an A. veronii biovar sobria strain (AS15), isolated from lamb kidney, was found to produce the highest enterotoxin score. An enterotoxin of c. 40 kDa produced by A, veron ii biovar sobria AS15 was purified by Sephacryl S-100 gel filtration and hi gh-performance liquid chromatography. This enterotoxin caused marked fluid accumulation in infant mice by the suckling mouse technique. The purified e nterotoxin cross-reacted with cholera toxin antibodies and was readily inac tivated by heating at 56 degrees C for 10 min. The production of a 'cholera -like' enterotoxin by Aeromonas isolates from samples of animal origin sugg ests that these organisms could be of public health significance in food pr oducts.