Synonyms: 5H-1-Pyrindinium,1-[(7-amino-2-carboxy-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-en-3-yl)methyl]-6,7-dihydro-,inner salt, (6R-trans)-;5H-Cyclopenta[b]pyridinium,1-[(7-amino-2-carboxy-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-en-3-yl)methyl]-6,7-dihydro-,inner salt, (6R-trans)-;