TLR9 and infection: Fig 5A shows that in WT mice, preceding H1N1 infection impairs clearance of MRSA relative to mice getting mock infection prior to MRSA. Furthermore, we were able to detect better bacterial clearance in the IAV-infected TLR9-/- mice 24 hours post-MRSA infection than in WT mice, but saw no difference in tissue injury (Fig 5B) or viral load (Fig 5C) in the presence or absence of MRSA between genotypes. Importantly, the difference we note in bacterial clearance at day 6 (24h post-MRSA infection) precedes the first deaths on day 7 (Fig 4B).