Panton-Valentine leukocidin-encoding bacteriophage and gene sequence variation in community-associated methicillin-resistant Staphylococcus aureus

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) often produce Panton-Valentine leukocin (PVL), which is encoded by two co-transcribed genes located on lysogenized bacteriophages. Six PVL-encoding temperate phages have been described and single nucleotide polymorphisms (SNPs) in the PVL genes have been reported. In the present study, 22 PVL-positive CA-MRSA isolates were chosen to reflect the diversity of multilocus sequence type (MLST) clonal complexes (CC) identified in our hospital. Isolates were characterized by antimicrobial resistance profile, staphylococcal cassette chromosome mec (SCCmec) and spa type, pulsed-field gel electrophoresis profile and MLST. Primers were designed to sequence the lukSF-PV genes. PVL-encoding phages were characterized using a PCR-based assay. SNPs were identified at seven locations in the lukSF-PV genes, which varied with S. aureus MLST lineage. One SNP was nonsynonymous. All CC80 and some CC1 isolates carried Theta Sa2mw; CC8, CC88 and CC154 isolates harboured PVL-encoding elongated head-type phages; and some CC59 isolates harboured a Theta Sa2958-like phage. Novel or variant phages were present in CC5 and some CC1 and CC59 isolates. The PVL gene sequence and the PVL-encoding phage varied with lineage. Further work is required to determine whether PVL sequence and/or phage variations result in biological differences.