Attachment of mesophilic aeromonads to cultured mammalian cells

The interaction between mesophilic aeromonads and cultured mouse adrenal cells was examined. Preliminary experiments indicated that aeromonad attachment was dependent upon inoculum size, incubation time, and incubation temperature. Optimal attachment was observed after 30 min of incubation at 37°C with an inoculum size of 1×10⁷ CFU. Heat-killed and formalin-treated organisms did not attach to the cultured cell system. The attachment of aeromonads to the mammalian cell surface was confirmed by light and scanning electron microscopy. Aeromonad attachment correlated both with the presence of pili and the specific aeromonad species, but not with hydrophobicity or the ability to autoagglutinate. Piliated strains were more likely to show high or moderate attachment.Aeromonas sobria, A. hydrophila, andA. veronii showed a greater ability to bind adrenal cells than didA. caviae. Removal of the pili from twoA. sobria isolates markedly reduced their attachment. In contrast, oneA. hydrophila isolate was strongly adherent after the removal of pili. The hemagglutination patterns produced byA. sobria and the other aeromonad species were distinctly different, but potentially predictive of the ability of aeromonads to attach to cultured mouse adrenal cells. These studies indicate that multiple mechanisms are important for the attachment of mesophilic aeromonads to mammalian cells. This model may prove useful for studying the pathogenesis of aeromonad infections.