Anti- Legionella activity of staphylococcal hemolytic peptides

► Various Staphylococci produced hemolytic peptides active towards Legionella. ► Group 1 peptides are bactericidal via permeabilization of the bacterial membrane. ► Group 2 peptides are bacteriostatic and poorly hemolytic. A collection of various Staphylococci was screened for their anti- Legionella activity. Nine of the tested strains were found to secrete anti- Legionella compounds. The culture supernatants of the strains, described in the literature to produce hemolytic peptides, were successfully submitted to a two step purification process. All the purified compounds, except one, corresponded to previously described hemolytic peptides and were not known for their anti- Legionella activity. By comparison of the minimal inhibitory concentrations, minimal permeabilization concentrations, decrease in the number of cultivable bacteria, hemolytic activity and selectivity, the purified peptides could be separated in two groups. First group, with warnericin RK as a leader, corresponds to the more hemolytic and bactericidal peptides. The peptides of the second group, represented by the PSMα from Staphylococcus epidermidis, appeared bacteriostatic and poorly hemolytic.