Adherence of Pseudomonas aeruginosa to respiratory epithelium and the effect of leucocyte elastase

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Abstract
The tracheobronchial secretions from patients with cystic fibrosis often contain high amounts of free proteases. To evaluate whether human leucocyte elastase (HLE) can favour the persistance of bacterial airways infection, we exposed the frog palate mucosa to HLE and then to radiolabeled Pseudomonas aeruginosa and followed the sequence of events by scanning electromicroscopy. In response to HLE there was a marked outpouring of mucus and a desquamation of the epithelium. P. aeruginosa was shown to adhere to recently secreted granules of mucus and to the exposed submucosal underlying connective tissues. For the eight diferrent bacterial strains studied, a significative adherence to HLE-injured mucosa was observed only in strains that possessed internal haemagglutinating activity. Neither the presence of fimbriae, nor of the mucoid exopolysaccharide, nor of the bacterial surface haemagglutinating activiy could be related to adherence of P. aeruginosa to the injured mucosa. These results support the hypothesis that HLE enhances bacterial infection of the respiratory mucosa both by inducing mucus hypersecretion and by exposing receptors to the microbial adhesions. It is also suggested that P. aeruginosa internal lectins may be implicated in adherence to host tissues.