PB-5266 A, B and C, new monobactams. I. Taxonomy, fermentation and isolation

New monobactams, PB-5266 A, B and C were isolated from the culture filtrate of Cytophaga johnsonae PB-5266 by various types of column chromatography and preparative reverse phase HPLC. PB-5266 A, B and C exhibited weak antibacterial activity against a sensitive mutant of Escherichia coli to beta-lactam antibiotics.