Effect of subinhibitory concentrations of azithromycin on adherence of Pseudomonas aeruginosa to bronchial mucins collected from cystic fibrosis patients

1Laboratoire de Bactériologie-Hygiène, Hôpital Calmette, Bd Pr J. Leclercq; 2Unité de Gastroentérologie, Hépatologie et Nutrition, Clinique de Pédiatrie, Hôpital Jeanne de Flandre, 2 Av Oscar Lambret, CHRU, 59037 Lille, France Sir, Pseudomonas aeruginosa, an opportunistic pathogen, is the major pathogen in the airways of patients with cystic fibrosis (CF) and is currently associated with the morbidity and mortality seen in this disease. Macrolides, such as azithromycin, are normally not included in the anti-pseudomonal therapeutic arsenal because of the absence of bactericidal or bacteriostatic activity. However, several previous investigators have reported that long-term administration of azithromycin is effective in patients with pulmonary P. aeruginosa infections.1 The clinical benefits achieved could include the effects of an anti-inflammatory2 and/or modulation of the production of virulence factors of P. aeruginosa, such as bacterial exoproducts,3 the formation of biofilm,4 or the synthesis of flagella3 and some outer membrane proteins.5 Adherence of P. aeruginosa to respiratory mucins plays an important role in the colonization of the airways of these patients. This adherence process involves flagella and several non-pilus adhesins localized on the outer membrane of P. aeruginosa. Supporting the clinical observations, adherence of this organism to human salivary or airway mucins has been demonstrated in vitro using liquid- or solid-phase adherence assays.6