(7aR,7R)-3-[({4-[(3Z)-5-{[(7aR,7R)-4-carboxy-3-{[(2-methyl-5,6-dioxo-1H-1,2,4-triazin-3-yl)sulfanyl]methyl}-6-oxo-2,6,7,7a-tetrahydroazeto[2,1-b][1,3]thiazin-7-yl]amino}-5-oxo-3-aza-2-oxapent-3-en-4-yl]-1,3-thiazol-2-yl}amino)methyl]-7-{[(3Z)-5-oxo-4-(1,3-thiazol-4-yl)-3-aza-2-oxapent-3-en-5-yl]amino}-6-oxo-2,6,7,7a-tetrahydroazeto[2,1-b][1,3]thiazine-4-carboxylic acid