Abstract
In 2008, an unusual strain of methicillin-sensitive Staphylococcus aureus (MSSA68111), producing both Panton-Valentine leukocidin (PVL) and toxic shock syndrome toxin-1 (TSST-1), was isolated from a fatal case of necrotizing pneumonia. Because PVL/TSST-1 co-production in S. aureus is rare, we characterized the molecular organization of these toxin genes in strain 68111. MSSA68111 carries the PVL genes within a novel temperate prophage we call ФPVLv68111 that is most similar, though not identical, to phage ФPVL – a phage type that is relatively rare worldwide. The TSST-1 gene (tst) in MSSA68111 is carried on a unique staphylococcal pathogenicity island (SaPI) we call SaPI68111. Features of SaPI68111 suggest it likely arose through multiple major recombination events with other known SaPIs. Both ФPVLv68111 and SaPI68111 are fully mobilizable and therefore transmissible to other strains. Taken together, these findings suggest that hypervirulent S. aureus have the potential to emerge worldwide.
Highlights
Staphylococcus aureus infections range in severity from superficial abscesses to complicated deep soft tissue infections and toxic shock syndrome (TSS) [1,2]
We describe the genetic makeup of the hypervirulent Toxic Shock Syndrome Toxin 1 (TSST-1)/PantonValentine leukocidin (PVL) co-producing MSSA isolated from this fatal case (MSSA68111; CC30) [9]
Our analysis showed that MSSA68111 produces 160.24 ng/mL PVL in 20-hr culture, which is significantly lower than that from the well-characterized PVL-producing MSSA strain ATCC49775 (Table 1), but comparable to that obtained from a clinical strain 934814 (USA300) (Table 1)
Summary
Staphylococcus aureus infections range in severity from superficial abscesses to complicated deep soft tissue infections and toxic shock syndrome (TSS) [1,2]. The pathogenesis of these diverse infections is attributed to multiple extracellular toxins including the PantonValentine leukocidin (PVL) and Toxic Shock Syndrome Toxin 1 (TSST-1). In 2005, one British report documented the TSST-1 gene in 4 of 30 PVL-positive isolates [7], one of which was associated with severe pneumonia [7]. Four of the 5 MRSA strains (80%) were multi-drug resistant Eight of these isolates (40%) were associated with serious diseases including pneumonia, empyema, deep-seated abscesses and toxic shock. One fatal case of necrotizing pneumonia was reported in a 14year-old child who presented initially with sore throat and pyrexia, and deteriorated rapidly, developing hypotension and multiple organ failure [9]
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