Comparison of S. aureus PVL-positive and PVL-negative isogenic strains in exponential and stationary phase of growth. Staphylococcus aureus

The Staphylococcus aureus Panton Valentine leukocidin (PVL) is a pore-forming toxin secreted by strains epidemiologically associated with the current outbreak of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) and with the often lethal necrotizing pneumonia. To investigate the role of PVL in pulmonary disease, we tested the pathogenicity of clinical isolates, isogenic PVL-negative and PVL-positive S. aureus strains, as well as purified PVL, in a mouse acute pneumonia model. Here we show that PVL is sufficient to cause pneumonia and that the expression of this leukotoxin induces global changes in transcriptional levels of genes encoding secreted and cell-wall-anchored staphylococcal proteins, including the lung inflammatory factor staphylococcal protein A (Spa). Keywords: comparative transcription profile in the presence or absence of PVL toxin Overall design: We conducted three independent microarray experiments (biological replicates) for each strain in exponential and stationary phase of growth. We calculated the fold change as the ratio between signal averages of three PVL-positive (LUG881) cultures (starting from a single colony) and three PVL-negative (LUG776) cultures (starting from a single colony) for each phase of growth.