TLR9 and infection: TLR9-/- mice infected with PR8 or MRSA alone did not differ in clearance of either pathogen from wild-type (WT) mice, but they experience improved survival post PR8-MRSA dual infection and show improved bacterial phagocytosis and killing post dual infection Our findings show a previously unrecognized role for TLR9 in limiting clearance of MRSA post-dual infection.