Usefulness of equilibrium parameters of adhesion in predicting the outcome of competition for bacterial receptor sites on respiratory epithelial cells by Pseudomonas aeruginosa strains of heterologous pilus

The adhesion of Pseudomonas aeruginosa strain O(PAO) to human buccal epithelial cells (BECs) was analysed by an equilibrium analysis of binding and the equilibrium parameters of adhesion determined. PAO bound to a maximum of 159 plus or minus 28 receptor sites per BEC with an apparent association constant (Ka) of 2 multiplied by 89( plus or minus 1 multiplied by 76) x 10 super(-8) ml/CFU. As P. aeruginosa strain K(PAK) employs pili to adhere to BECs and there is substantial homology between the PAK pilin gene and the PAO pilin gene, the potential for competition for receptor sites on the BEC surface was investigated. PAO and PAK competed for receptor sites in a reciprocal manner, although PAO was similar to 10 fold more effective in competing for receptor sites than was PAK.