The enzymes lysozyme and peroxidase, defensins, cystatins and an antibody, IgA, are all antibacterial. Lysozyme and phospholipase A2 both have clear antimicrobial activity. The principal proteins are alpha-lactalbumin, lactoferrin (apo-lactoferrin), IgA, lysozyme, and serum albumin. The lysozyme enzyme can also damage bacterial cell walls. In addition to defensins, Paneth cells secrete lysozyme, tumor necrosis factor-alpha, and phospholipase A2. In addition, a bactericidal effect is generated by nasal mucus which contains the enzyme lysozyme. The enzyme lysozyme has adapted to facilitate digestion of bacteria in the ruminant abomasum. Chitin has also been shown to be a viable lysozyme substrate. The addition of lysozyme, nitrate, nitrite and propionic acid salts inhibits clostridia in various foods. Hen egg lysozyme, an antibiotic protein found in chicken eggs, is also sweet. A tear protein analysis test measures the lysozyme contained within tears. Tears are also beneficial to wounds due to the lysozyme enzyme. The outer membrane provides these bacteria with resistance to lysozyme and penicillin. The His31-Asp70 salt bridge in T4 lysozyme was buried within the protein. "Kocuria" is susceptibility towards bacitracin and lysozyme and resistance to nitrofurantoin, furazolidone and lysostaphin.