Bacterial adherence to virus-infected respiratory tract cells may be one of the several mechanisms whereby virus predisposes to bacterial pneumonia. To evaluate the effect of influenza virus infection on pneumococcus adhesion, 39 mice were infected with PR8/A influenza virus. The adherence of radiolabeled pneumococcus to mice tracheal cells was determined 2, 4, and 6 days after viral inoculation. The pneumococcal adhesion to infected tracheas was significantly enhanced on Day 6 (p less than 0.001). Scanning and transmission electron microscopy revealed that by the fourth and sixth days after virus inoculation, the ciliated and the secretory cells of the tracheal epithelium had desquamated and the mucosa were coated with a continuous layer of basal cells. In a few cases, a desquamation of the basal layer was observed and the exposed basement membrane appeared as a pole of attraction for bacteria. Pneumococci were never seen attached to control tracheas. In contrast, they were observed adhered to the microvilli of the basal cells and, to a greater extent, to the exposed basement membrane.
It has recently been suggested that in cystic fibrosis (CF), there is no rheological abnormality of airway secretions other than that associated with purulence, and that the apparent inhibition in the mucociliary transport rate might be partly due to a ciliary inhibitor present in these secretions. In order to ascertain this assumption, expectorated airway secretions were collected without salivary contamination in twenty-four CF patients and the rheological properties were measured. Using a photometric method, the effects of CF sputum samples were analysed on the ciliary beat frequency (Fm) of the frog palate, and we measured their mucociliary transport rate (TR). In all but one CF sputum, TR and Fm were lower than that of the control frog mucus (median TR: 18.7 and 11.6 mm min-1; median Fm: 12.3 and 11.3 Hz, respectively). In the eighteen patients in whom the rheological properties were outside the range for optimal mucociliary transport, the clinical Shwachman score was significantly (P less than 0.05) lower (median score: 66.2 points) than in the six patients with optimal rheologic properties (median score: 73 points). In the eleven CF patients with superinfection, the apparent viscosity (eta o) was significantly higher (P less than 0.01; median eta o: 24.4 Pa. s) and TR, expressed as a percentage of the reference value, was significantly lower (P less than 0.05; median Tr: 54.5%) in comparison with the values obtained for the thirteen non-superinfected CF patients (median eta o: 15 Pa. s and median TR: 66% respectively). The CF patients with markedly hyperviscous sputum (eta o higher than 30 Pa. s) exhibited a low Shwachman score.
Summary. 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 persistence of bacterial airways infection, we exposed the frog palate mucosa to HLE and then to radiolabelled Pseudomonas aeruginosa and followed the sequence of events by scanning electronmicroscopy. 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 different 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 activity 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 adhesins. It is also suggested that P. aeruginosa internal lectins may be implicated in adherence to host tissues.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.