Distribution of the synergistic haemolysin genes hld and slush with respect to agr in human Staphylococci

Several staphylococcal species express a synergistic activity which potentiates hemolysis by beta-hemolysin. In Staphylococcus aureus, this activity is mediated by the delta-hemolysin, coded by the hid gene within the agr locus. In S. lugdunensis, the equivalent activity results from the production of 3 small peptides coded by an operon named slush, distinct from hid and located outside the agr region. We examined 15 clinically relevant staphylococcal species for the presence of hid, slush and agr by specific hybridisation. All species contained a recognizable agi-related locus. Three species never produced synergistic haemolysis and contained neither hid nor slush. Of the 12 producer strains, 5 contained hid, apparently within the agr region, 4 contained slush and one (S. caprae) contained both. Two other producer species (S. hominis and S. simulans) hybridised to neither probe.