DSG1 and dermatitis: When S. hyicus ACCC 61734 invades piglets, protein A can inhibit the phagocytic ability of phagocytes, effectively reduce the piglets’ ability to resist bacteria [47,48] and make S. hyicus ACCC 61734 colonize the skin surface successfully and then the ExhD, an exotoxin secreted by S. hyicus ACCC 61734, plays the role of molecular scissors to specifically digest epidermal Dsg1, so that bacteria can invade from the skin surface to the deep layer and even to the blood circulation system (Figure 6F), causing sebum overflow, and forming dermatitis and viscera lesions (Figure 6).