Rattus norvegicus: not a model for Aeromonas-associated gastroenteritis inman

The lack of a suitable animal model of Aeromonas-associated diarrhoea has h ampered investigations into Aeromonas pathogenic mechanisms. Hence, a publi shed report that clindamycin-pretreated rats developed signs and symptoms o f enteritis following intragastric inoculation of an Aeromonas strain requi red further investigation. Although we could demonstrate long-term colonisa tion (>12 days) and histological damage in this animal model with Pseudomon as aeruginosa isolated from patients with chronic diarrhoea, this was not s een with Aeromonas spp. Six Aeromonas strains, selected for their potential virulence and colonising abilities and including the strain from the origi nal report, were either not recovered from stools or were recovered for no longer than 2 days post inoculation. Intestinal histology remained normal. Destruction of bacteria in vivo appeared to be due to immune mechanisms as inoculum strains were not 'suicidal' or unduly sensitive to low pH or clind amycin. This study was, therefore, unable to validate the clindamycin-treat ed rat model as a useful one for investigating the enteropathogenicity of A eromonas species. Possible reasons for the discrepancy between our study an d the original report are discussed. (C) 2000 Federation of European Microb iological Societies. Published by Elsevier Science B.V. All rights reserved .