Consequently, NOD1-deficient mice display an increased vulnerability to a number of microbial pathogens including Helicobacter pylori, Streptococcus pneumoniae, and Clostridium difficile (20–22), whereas mice with deficiency in NOD2 were more susceptible to infections caused by Streptococcus pneumoniae, Citrobacter rodentium, and Staphylococcus aureus (23–25). This evidence concerns the gene NOD2 and infection.