The effect of influenza virus on the adherence of Haemophilus influenzae to human cells in tissue culture.

The adherence of eleven strains of Haemophilus influenzae to MRC5 cells was studied and compared with adherence of the same eleven strains to MRC5 cells infected with influenza A/NWS/33 virus. Per cent Adhesion (the proportion of cells to which more than two bacteria were adhering) was estimated. Organisms grown on solid media adhered better than those grown in liquid media though the difference was not statistically significant (t test for independent means). A wide range of % Adhesion values for organisms grown on solid media to control cells was exhibited (1-88%). Ten of eleven strains grown on solid media or in broth showed increased adherence to influenza virus infected cells; this difference was significant (P less than 0.05, t test for independent means). The effect of virus infection in increasing % Adhesion was inversely proportional to the adhesiveness of the strain in question to uninfected cells. Strains that adhered most efficiently to control cells showed little increase in % Adhesion following virus infection, while strains that adhered poorly to control cells showed large increases in % Adhesion following virus infection.