(7aR,7R)-7-{[(4Z)-5-[2-({[(7aR,7R)-7-{[(4Z)-2-carboxy-5-(2-{[3-(hydroxymethyl)-1,2-dioxo-4-sulfanylbutyl]amino}-1,3-thiazol-4-yl)-2-methyl-6-oxo-4-aza-3-oxahex-4-en-6-yl]amino}-4-carboxy-6-oxo-2,6,7,7a-tetrahydroazeto[2,1-b][1,3]thiazin-3-yl]methyl}amino)-1,3-thiazol-4-yl]-2-carboxy-2-methyl-6-oxo-4-aza-3-oxahex-4-en-6-yl]amino}-6-oxo-3-(pyridin-1-ium-1-ylmethyl)-2,6,7,7a-tetrahydroazeto[2,1-b][1,3]thiazine-4-carboxylate