By adding NS-398, a small-molecule specific inhibitor of COX-2, into the culture of HOK with or without S. aureus infection, we found that the level of PGE2 both decreased remarkably and the S. aureus-stimulated increase of PGE2 production by HOK infection was disappeared, displaying a similarly low level to that in control cell (Fig 1B). This evidence concerns the gene PTGS2 and infection.