Characterization of anti-Legionella activity of warnericin RK and delta-lysin I from Staphylococcus warneri

Legionella pneumophila, the causative agent of Legionnaires’ disease, is a waterborne bacteria. It can multiply in man-made water systems and infect people who inhale contaminated droplets. We have previously reported a Staphylococcus warneri strain that display an anti-Legionella activity. In this work, we characterized three anti-Legionella peptides that are produced by S. warneri. One peptide, warnericin RK, is original, while the two others are delta-lysin I and delta-lysin II, whose genes were previously described. Due to high sequence similarity of the two delta-lysins, further characterization was performed only on delta-lysin I. Warnericin RK and delta-lysin I displayed the same antibacterial spectrum, which is almost restricted to the Legionella genus. Also, both peptides have a hemolytic activity. These results led to the hypothesis that warnericin RK and delta-lysin I share a similar mode of action, and that Legionella should have a specific feature that may explain the high specificity of these antibacterial peptides.