MUC5AC and bacterial vaginosis: In women with bacterial vaginosis, the overgrowth of anaerobic gram-negative bacteria that produce sialidase, glycosidases and other mucin-degrading enzymes causes a breakdown in the barrier properties of cervicovaginal mucus, thereby destroying the mucus gel and helping other sexually transmitted pathogens such as human immunodeficiency virus (HIV) to invade [52].