In particular, the co-infection of a few strains from S. mitis (SM2, SM3, SM4 and SM11) with P. aeruginosa led to more than 9-fold reductions (p<0.0001) of IL-8 compared to that of P. aeruginosa mono-infection, indicating protective effects of these S. mitis strains on the host. Here, CXCL8 is linked to coinfection.