Isolation and characterization of a Staphylococcus warneri strain producing an anti-Legionella peptide.

Legionella pneumophila is a pathogenic bacterium found in freshwater environments that is responsible for pneumonia. People become infected through inhalation of contaminated droplets from water devices, such as cooling towers and showers. It is important to find new treatments that decrease the development of Legionella. We found a Staphylococcus warneri strain that inhibits Legionella growth. This activity is due to a molecule secreted by S. warneri. This molecule displayed a high heat-stability and its activity was lost after protease treatments, suggesting that it might be a bacteriocin. Its purification led us to conclude that this anti-Legionella molecule is an highly hydrophobic peptide. It has an original and very specific spectrum of activity, directed only toward the Legionella genus. This is the first description of an antibacterial peptide active against Legionella.