<chemical> A semisynthetic cephamycin antibiotic with a broad spectrum of activity against both gram-positive and gram-negative microorganisms. It has a high rate of efficacy in many types of infection and to date no severe side effects have been noted. ... Pharmacological action: cephamycins. ... Chemical name: 5-Thia-1-azabicyclo(4.2.0)oct-...