Searching for Virulence Factors among Isolates from Orthopedic Infections: Correlation of , and Genes with Hemolytic Activity and Synergistic Hemolytic Activity.

is an emerging high-virulent pathogen. Here, the presence and expression of virulence genes (, , , , , and , and genes of the putative and ) and the ability to induce synergistic hemolytic activity and hemolysis after 24, 48 and 72 h were investigated in a collection of twenty-two clinical isolates. The collection of isolates, mainly from implant orthopedic infections, had previously been grouped by ribotyping/dendrogram analysis and studied for biofilm matrices, biomasses and antibiotic resistances. Two isolates, constituting a unique small ribogroup sharing the same cluster, exhibited an amplicon size of the operon ( synergistic hemolysin) which was shorter than the expected 977 bp. This outcome can predict the genetic lineage of the strains. One isolate (1342) presented two deletions: one of 90 bp in and the other of 91 bp in . Another isolate (N860314) showed a single 193 bp deletion, which encompassed part of the terminal sequence and most of . The isolate N860314 was devoid of hemolytic activity after 24 h, and the first consideration was that the deleted region deals with the coding of the active enzymatic site of the slush hemolysin. On the other hand, 1342 and N860314 isolates with different deletions and with hemolytic activity after 24 and 48 h, respectively, could have replaced the hemolytic phenotype through other processes.