Novel phospholipase A activity secreted by Legionella species

Bacterial phospholipases are regarded as a major virulence factor in infect ion. In bacteria associated with pneumonia, destruction of lung surfactant and host cell membranes by bacterial phospholipases secreted during infecti on is thought to contribute to the disease, Phospholipase C (PLC) activity has been described in several Legionella species (W. B. Baine, J. Gen, Micr obiol. 134:489-498, 1988; W. B, Baine, J. Gen. Microbiol. 131:1383-1391, 19 85), By using detection methods such as thin-layer chromatography and mass spectrometry, PLC activity could not be detected in several strains of Legi onella pneumophila. Instead, phospholipid degradation was identified to be caused by a novel PW activity. We could demonstrate that PLA secretion star ts at the mid-exponential-growth phase when bacteria were grown in liquid c ulture. Several Legionella species secreted different amounts of PLA. Legio nella PLA may act as a powerful agent in the mediation of pathogenicity due to destruction of lung surfactant and epithelial cells.