Synergistic hemolytic activity of Staphylococcus lugdunensis is mediated by three peptides encoded by a non-agr genetic locus

Some strains of the coagulase-negative Staphylococcus lugdunensis produce a synergistic hemolytic activity (SLUSH), phenotypically similar to the delta-hemolysin of S. aureus, Reverse-phase high-pressure liquid chromatography of supernatants from S, lugdunensis 307 yielded three late-eluting peaks of 3.5 kDa with synergistic hemolytic activity, A degenerate oligonucleotide probe was designed from partial amino acid sequences of the 23-amino-acid (aa) tryptic fragments from one of the three peaks and hybridized to a single 2.8-kb HindIII chromosomal fragment, The relevant portion of this fragment was cloned by PCR, and sequencing showed the presence of three related open reading frames (ORFs), SLUSH-A, SLUSH-B, and SLUSH-C, preceded by an unrelated short potentially coding sequence (ORF-X), cotranscribed on a polycistronic 838-nucleotide mRNA, The amino acid sequences of the peptides from the three peaks align perfectly with the predicted sequences from the three SLUSH ORFs (peak I = SLUSH-B; peak II = SLUSH-C; peak III = SLUSH-A), These three peptides are closely related (amino acid homology, >76%) and do not show significant homology to S, aureus delta-hemolysin but do resemble a Salmonella typhimurium invasin and the ''gonococcal growth inhibitor,'' a bacteriocin secreted by Staphylococcus haemolyticus. The predicted ORF-X gene product is a 24-aa peptide with no homology to the SLUSH peptides.