Prevalence and Sequence Variation of Panton-Valentine Leukocidin in Methicillin-Resistant and Methicillin-Susceptible Staphylococcus aureus Strains in the United States

Panton-Valentine leukocidin (PVL), encoded by the lukSF-PV genes, is a putative virulence factor and marker for community-associated methicillin-resistant Staphylococcus aureus. Here we report the prevalence of PVL among a representative sample of 1,055 S. aureus infection isolates from the United States and describe the sequence variation of the lukSF-PV genes. We performed multilocus sequence typing (MLST) on all isolates and sequenced fragments of the lukSF-PV genes from a sample of 86 isolates. We assigned isolates to a PVL R or H sequence type based on a polymorphism that results in an amino acid change from arginine (R) to histidine (H). Overall, we found that 36% of S. aureus isolates were positive for lukSF-PV. Among the 86 we typed, we identified 72 R variants and 14 H variants. Among the 47 methicillin-resistance S. aureus (MRSA) isolates, 43 harbored the R variant, and among the 39 methicillin-susceptible S. aureus (MSSA) isolates, 29 harbored the R variant. Almost all (97%) of the R variants were found in MLST clonal complex 8 (CC8), while the H variant was broadly distributed among 6 CCs. Within CC8, all 38 MRSA (USA300) and all 28 MSSA isolates harbored the R variant. Of the 20 isolates from blood and the lower respiratory tract, 19 (95%) harbored the R variant. While the R variant had been linked primarily to USA300 MRSA, we found that all CC8 MSSA isolates also contained the R variant, suggesting that some strains of USA300 may have lost methicillin resistance as an adaptation in the community.