An objective of the present invention is to provide carbapenem derivatives which have potent antibiotic activity against MRSA, PRSP, Influenzavirus, and &bgr;-lactamase-producing bacteria and are stable against DHP-1. The compounds according to the present invention are compounds represented by formula (I) or pharmaceutically acceptable salts thereof:
1
wherein R
1
represents H or methyl; R
2
and R
3
represent H, a halogen atom, alkyl or the like; and R
4
represents substituted lower alkylthio or the like.