Sulfazecin and isosulfazecin, novel beta-lactam antibiotics of bacterial origin

In the long history of screening for antibiotics, fungi and actinomycetes have been the only producers of beta-lactam antibiotics although several phytopathogenic bacteria have been reported to produce toxins with a beta-lactam structure. We report here the first evidence that novel monocyclic beta-lactam antibiotics, sulfazecin and isosulfazecin, are produced by new species of Pseudomonas.