Panton-Valentine leukocidin (PVL) is a cytolytic toxin, and its genes are encoded on a S. aureus bacteriophage integrated into the bacterial genome. PVL may be the key toxin responsible for enhanced virulence of community-associated methicillin-resistant S. aureus (CA-MRSA), but this is controversial. In many bacteria, expression of toxin genes encoded on such phage are induced under stress, including antibiotics. In this issue, Wirtz et al. prove that phage induction increases expression of PV-luk mRNA dramatically. But suprisingly, they show that the clone responsible for most CA-MRSA infections in the USA have defective phage and fail to overexpress the toxin.
via For CA-MRSA, how much PVL is too much? — Lindsay, 10.1099/mic.0.034041-0 — Microbiology.
