Panton-Valentine leukocidin

Panton-Valentine leukocidin (PVL) is a cytotoxin&mdash;one of the &beta;-pore forming toxins. Presence of PVL is associated with extremely high virulence in species of Staphylococcus aureus. It is nearly always found in isolates of community-acquired S. aureus infections. PVL is produced from the genetic material of a bacteriophage which infects Staphylococcus aureus, making it more virulent.

History
It was initially discovered by Van deVelde in 1894 due to its ability to lyse leukocytes. It was named after Panton and Valentine when they associated it with soft tissue infections in 1932.

Clinical effects
PVL causes leukocyte destruction and necrotizing pneumonia, an aggressive condition that often kills patients within 72 hours. It has played a role in a number of outbreaks of fatal bacterial infections. PVL may increase the expression of staphylococcal protein A, a key pro-inflammatory factor for pneumonia.

Epidemiology
Community-acquired Methicillin-resistant Staphylococcus aureus (CA-MRSA) is particularly difficult to treat when it carries PVL. Genetic analysis shows that PVL CA-MRSA has emerged several times, on different continents, rather than being the worldwide spread of a single clone.