Superantigens in Staphylococcus aureus isolated from prosthetic joint infection

• Staphylococcus aureus is a frequent cause of prosthetic joint infection (PJI).
• The prevalence of superantigens (SAgs) among PJI-associated S. aureus is unknown.
• Close to 90% of S. aureus PJI isolates carried at least 1 SAg gene.
• seg and seh were the most and least common SAgs, respectively.
• Most SAg-carrying isolates produced biologically active SAgs in biofilms in vitro.

Staphylococcus aureus is a common cause of prosthetic joint infection (PJI). The prevalence of superantigens (SAgs) among PJI-associated S. aureus is unknown. Eighty-four S. aureus isolates associated with PJI isolated between 1999 and 2006 were studied. SAg genes, sea, seb, sec, sed, see, seg, seh, sei, and tst, were assayed by PCR. Seventy-eight (92.9%) isolates carried at least 1 SAg gene studied, with 61 (72.6%) harboring more than 1. seg was most commonly (70.2%), and seh was least frequently (4.8%) detected. tst-positive isolates were associated with early infection and increased erythrocyte sedimentation rate at diagnosis (P = 0.006 and P = 0.021, respectively). seg and sei were associated with methicillin resistance (P = 0.008 and P = 0.002, respectively). A majority of PJI-associated isolates studied produced biologically active SAgs in both planktonic and biofilm growth modes. SAg genes are prevalent in S. aureus causing PJI.