(5R,5β)-3-(Ethylthio)-6β-[(R)-1-hydroxyethyl]-7-oxo-4-thia-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylic acid sodium salt

sodium [5R-[5alpha,6alpha(R*)]]-3-(ethylthio)-6-(1-hydroxyethyl)-7-oxo-4-thia-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylate