ADHESION TO AND INVASION OF HUMAN COLON-CARCINOMA CACO-2 CELLS BY AEROMONAS STRAINS

The enteropathogenicity of Aeromonas strains that showed mannose-resis tant adhesion to INT407 cells was evaluated by infecting Caco-2 cells and observing them by light and electronmicroscopy. Five of six strain s adhered in large numbers to Caco-2 cells in the presence of mannose and caused cytopathic effects. Two strains of Aeromonas spp. seemed to invade Caco-2 cells, as membrane-bound bacteria were seen within the cytoplasm of these cells; however, staining by acridine orange-crystal violet appeared to show intracellular fluorescent bacteria in three s trains. Fimbriae did not appear to play an important role in adhesion because fimbrial structures were not seen by transmission electronmicr oscopy. Adhesion of four strains was inhibited by the addition of L-fu cose. The strains were negative in the fluorescence actin staining tes t, which in enteropathogenic Escherichia coil strains correlates with the ability to attach and efface intestinal microvilli. The DNA of the Aeromonas strains did not hybridise with the E. coli eae and ipaB pro bes, associated with attaching and effacing ability and invasion, resp ectively. These results give support to the enteropathogenicity of adh esive strains of Aeromonas spp., although the mechanisms of adhesion, and possibly invasion, remain to be elucidated.