Carbapenem drug molecule. Ball-and-stick molecular model of carbapenem, an antibiotic often used as a last-resort treatment of bacterial infections such as Escherichia coli (E. coli) or Klebsiella pneumoniae. Carbapenems are effective against both Gram-positive and Gram-negative bacteria as well as anaerobes, and are resistant to bacterial enzymes which try to break down antibiotics. However recent strands of carbapenem-resistant bacteria are beginning to emerge, leading to concerns over the possible spread of a mutated antibiotic-resistance gene. Atoms are represented as spheres with conventional colour coding: hydrogen (white), carbon (black), oxygen (red), and nitrogen (blue).