The Effect of Piliation and Exoproduct Expression on the Adherence of Pseudomonas aeruginosa to Respiratory Epithelial Monolayers

Abstract

The adherence properties of Pseudomonas aeruginosa strains with known pilin DNA sequences were studied. A polar pilus clearly contributed to adherence, as 35S-labeled pilus-positive (Pil⁺) strains bound significantly more to bovine trachea epithelial monolayers than did pilus-negative (Pil⁻) mutants (P < .05) and minimally more than hyperpiliated strains. A pil⁻ mutant PAK/NP, constructed by gene replacement, demonstrated low levels of attachment (3.8% of the inoculum adherent compared with 7% for the wild-type strain PAK), suggesting that other adhesins are functional. The Pil⁻, flagellum-negative strain PAO1150.l bound the least (0.3% of the inoculum adherent), confirming the importance ofmotility in the binding process. The pilin sequences of strains P1 and PAl244 were virtually identical, although P1 bound threefold more than did PA1244. P1 produced lo-fold more proteinase than did PA1244, and a proteinase-negative mutant of P1, isolated by transposon mutagenesis, had binding equivalent to that of PA1244. The adherence of PAOl was increased 60% in the presence of bacterial supernatants from phosphatelimited cultures and correlated with phospholipase C activity in the supernatant. Thus, the expression of several Pseudomonas genes may be required to promote efficient binding to epithelial surfaces.