Meropenem trihydrate Imp. A (EP):(4R,5S)-5-[(1S,2R)-1-carboxy-2-hydroxypropyl]-3-[[(3S,5S)-5-[(dimethylamino)carbonyl]pyrrolidin-3-yl]sulfanyl]-4-methyl-4,5-dihydro-1H-pyrrole-2-carboxylic acid.