A BETA-LINKED MANNAN INHIBITS ADHERENCE OF PSEUDOMONAS-AERUGINOSA TO HUMAN LUNG EPITHELIAL-CELLS

Adherence through carbohydrate-binding adhesins is an early step in co lonization of the lung by gram-negative organisms, and because publish ed data indicate that binding involves mannose groups, we tested the a bility of a beta-linked acetylmannan (acemannan) to inhibit adherence of Pseudomonas aeruginosa to cultures of human lung epithelial cells, Adherence of radiolabelled P.aeruginosa to A549 cells (a type II-like pneumocyte line) increased linearly with the duration of the incubatio n, Acemannan inhibited adherence of bacteria, and the extent of inhibi tion was related to the concentration of the mannan, Inhibition requir ed continued contact between acemannan and the target epithelial cells ; cells washed free of acemannan no longer discouraged bacterial bindi ng, Comparison of binding between seven different strains of P.aerugin osa indicated that fewer mucoid than non-mucoid bacteria adhered, but binding of either phenotype was inhibited by acemannan. Mannose, methy l alpha-D-mannopyranoside, methyl beta-D-mannopyranoside and dextran d id not affect adherence of any of the non-mucoid strains, Mannose inhi bited adherence by one mucoid strain, but not the other, indicating di fferences between strains of the same phenotype. Since prior treatment of epithelial cells with concanavalin A did not affect acemannan-indu ced inhibition of bacterial adherence, we concluded that the inhibitor y effect of acemannan probably does not involve mannose-containing rec eptors.