Phospholipase A secreted by Legionella pneumophila destroys alveolar surfactant phospholipids

Destruction of alveolar surfactant phospholipids by bacterial phospholipase s is suggested to be a major virulence factor involved in bacterial pneumon ia. Since Legionella pneumophila secretes phospholipase A, we analyzed phos pholipid degradation in natural bovine surfactant by L. pneumophila. Phosph olipids were reduced in amount after incubation with bacteria or culture su pernatant of L. pneumophila serogroup 6. Free fatty acids and lysophosphati dylcholine were formed, the latter is known to be highly cytotoxic. Surface tension of surfactant as determined by pulsating bubble surfactometer incr eased significantly compared to the control. Phospholipase A activity seems to be a powerful agent of legionellae in causing lung disease. (C) 2000 Pu blished by Elsevier Science B.V. on behalf of the Federation of European Mi crobiological Societies.