Ro 22-5417, a new clavam antibiotic from Streptomyces clavuligerus. I. Discovery and biological activity.

Streptomyces clavuligerus NRRL 3585, a culture which produces a variety of beta-lactam antibiotics in the penicillin, cephalosporin and clavam families, was found to produce a new beta-lactam antibiotic, Ro 22-5417. The compound, which was neither a substrate for nor inhibitor of several beta-lactamases, showed antimicrobial activity in defined minimal medium but little or no inhibitory activity in nutrient-rich medium. The activity was bacteriostatic against Bacillus species ATCC 27860 and was antagonized by D- and L-methionine, L-cystathionine, L-homocystine and O-acetyl-L-homoserine but not by L-homoserine, L-aspartate, L-cysteine or other common amino acids, vitamins and nucleosides. Our results are consistent with Ro 22-5417 acting as an inhibitor in methionine biosynthesis.