In vitro antibacterial activity and beta-lactamase stability of CP-70,429 a new penem antibiotic.

In in vitro susceptibility tests, the new penem CP-70,429 showed potent antibacterial activity against gram-positive and gram-negative bacteria except Pseudomonas aeruginosa and Xanthomonas maltophilia. CP-70,429 was stable to various types of beta-lactamases except for the enzyme from X. maltophilia and was 16- to 128-fold more active than the other compounds against beta-lactamase-producing strains of Enterobacter cloacae and Citrobacter freundii.