Effect of salmeterol on Haemophilus influenzae infection of respiratory mucosa in vitro

Haemophilus influenzae is a common bacterial pathogen causing human respirator tract infections. We have previously shown that the beta(2)-agonist salmeterol reduces damage to the respiratory mucosa caused by Pseudomonas aeruginosa in vitro. We have now investigated the effect of salmeterol on H. influenzae infection of adenoid tissue in an organ culture by scanning electron microscopy. Tissue was preincubated with or without salmeterol (4x10(-7)M), prior to infection with H. influenzae and incubated for 12 or 24 h. Infected organ cultures had increased epithelial damage and decreased numbers of both ciliated and unciliated cells at 12 h, which were significantly different (p less than or equal to 0.01) from the controls at 24 h, Salmeterol (4x10(-7)M) significantly (p less than or equal to 0.03) reduced damage and loss of ciliated cells in infected organ cultures at both 112 and 24, and significantly (p less than or equal to 0.03) reduced lass of unciliated cells at 24 h. Salmeterol had no effect on the density of bacteria adhering to each individual mucosal feature or the total number of bacteria adhering to the organ culture, These results suggest that salmeterol protects the respiratory epithelium against Haemophilus influenzae-induced damage, The mechanism of salmeterol cytoprotection and its potential clinical relevance remain to be investigated.