Pyridinium. 4-[2-[[(6R.7R)-2-carboxy-7-[[(2Z)-2-(ethoxyimino)-2-[5-(phosphonoamino)-1.2.4-thiadiazol-3-yl]acetyl]amino]-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-en-3-yl]thio]-4-thiazolyl]-1-methyl-. inner salt