Why is Panton Valentine Leukocidin (PVL) important for the virulence of community–associated MRSA?
PVL is a leukocidin, which means it targets and destroys neutrophils, the first line of the human innate immune defense against bacterial infection. Although PVL has an extraordinary epidemiologic link with CA-MRSA infection, studies in rodents have not conclusively shown that PVL accounts for the elevated virulence phenotype. USA300 CA-MRSA strains are highly virulent in rodent models of infection whether or not the PVL gene is present. This has been shown using isogenic knockout strains of PVL+ and PVL- MRSA as well as with many clinical isolates that are naturally PVL positive and negative. However, such studies do not rule out the possibility that PVL plays a role in the ability of S. aureus to persist and disseminate among healthy human hosts. It is also possible that PVL does play a role in virulence but animal models of infection do not mimic the situation in humans.
