Two new monobactam antibiotics produced by a Flexibacter sp. I. Taxonomy,fermentation,isolation and biological properties.

Abstract
Two new .beta.-lactam antibiotics, SQ 28502 and SQ 28503, were isolated from fermentations of a Flexibacter sp. They are demethoxy monobactams with oligopeptide side chains and have MW of 1462 and 1446, respectively. These .beta.-lactams showed a high degree of stability to a variety of .beta.-lactamases and were irreversible inactivators of P99 .beta.-lactamase from Enterobacter cloacae. They exhibited weak antibacterial activity.