Many studies have investigated the correlation between the invasion of PAs and several biological markers, including matrix metalloproteinase-9 (MMP9), matrix metalloproteinase-2 (MMP2), tissue inhibitor of metalloproteinases-2 (TIMP2), and pituitary tumor transforming gene 1 protein (PTTG1, also called securin) (8–13). Here, MMP9 is linked to gonorrhea.