Imipenem antibiotic drug, molecular model. Imipenem belongs to the carbapenem group of antibiotics. Bacteria are becoming increasingly resistant to carbapenems due to the bacterial enzyme NDM-1 (New Delhi metallo-beta-lactamase 1). This enzyme, which was first found in bacteria from the Indian subcontinent, is now being found in bacteria in the UK. Atoms are represented as spheres with conventional colour coding: hydrogen (white), carbon (grey), oxygen (red), nitrogen (blue), sulphur (yellow).