IF staining showed that PAO1, when co-infected with USA300, penetrated significantly deeper into the tissue (623.8 ± 150.9 μm) compared to mono-infection (363.5 ± 154.8 μm) or co-infection with crtM::Tn (330.2 ± 54.81 μm) (Fig. 4 C and E). This evidence concerns the gene MATN1 and infection.