C3 and susceptibility to pneumonia measurement: We hypothesized that inflammatory and immune system diseases caused by S. aureus are likely regulated by three genes: jun, c3, and spil. Staphylococcus aureus is the most common pathogen that causes inflammatory and immune system diseases, including a variety of suppurative (pus-forming) infections (Carrel et al., 2017), pneumonia, pseudomembranous colitis, pericarditis, and even sepsis (Agarwal et al., 2018).