A rare but often lethal cocktail that can complicate flu

Panton-Valentine leukocidin (PVL) is one of many toxins produced by Staphylococcus aureus. Structurally similar to γ haemolysin, this leukocidin comprises two subunits (F and S) that together are leukocidal and dermonecrotic.1 Intermixing of γ haemolysin and the subunits of PVL produces toxin molecules with varying cellular affinities and destructive capability, even when the staphylococci may be otherwise sensitive to antibiotics such as methicillin. The death of a fit young soldier in the United Kingdom earlier this year from toxicity to PVL illustrated the extent of that capability.2

Infection with PVL producing staphylococci is rare. Fewer than 2% of clinical isolates of S aureus examined in the United Kingdom in 2002-3 had the genes to produce the leukocidin, although it was found in 4.6% of samples from infections of skin and soft tissue.3 Furthermore, “pure” disease caused by those S aureus bacteria that produce PVL is rarely life threatening. It presents as recurrent furunculosis or abscesses, it may be either sensitive or resistant to methicillin, and it can be difficult to eradicate among carriers. Three new and more virulent staphylococcal syndromes associated with the leukocidin—purpura fulminans, skin sepsis, and necrotising pneumonia—have been recognised recently, …