In vitro activity and beta-lactamase stability of a new monobactam, B0-1165

B0-1165 is a 1-carboxy-1-cyclopropoxyamino,4-fluoromethyl monobactam. It inhibited the majority of Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Citrobacter diversus, Aeromonas hydrophila, Proteus mirabilis, Proteus vulgaris, Providencia rettgeri, Providencia stuartii, Yersinia enterocolitica, Haemophilus influenzae, Neisseria gonorrhoeae, and Salmonella and Shigella species at less than or equal to 0.125 microgram/ml. Overall, its in vitro activity was similar to that of aztreonam, cefotaxime, and ceftazidime, with minor differences in the MICs for individual isolates. Enterobacter species and Citrobacter freundii which were derepressed for beta-lactamase production and had higher MICs of aztreonam and ceftazidime had MICs that ranged from 4 to 32 micrograms/ml. B0-1165 had activity against Pseudomonas aeruginosa similar to that of aztreonam but lower than that of ceftazidime and carumonam. Pseudomonas maltophilia and other Pseudomonas species were resistant or had MICs of 32 micrograms/ml, as did Acinetobacter species. B0-1165 did not inhibit streptococcal, staphylococcal, or anaerobic species, such as Clostridium and Bacteroides species. B0-1165 was not hydrolyzed to any appreciable extent by common plasmid- and chromosomally Richmond-Sykes type 1a-, 1c-, and 1d-mediated beta-lactamases. It inhibited the Enterobacter cloacae P99 and inducible Pseudomonas aeruginosa beta-lactamases. B0-1165 was a poor inducer of beta-lactamase, but exposing E. cloacae and C. freundii to B0-1165 selected for resistant isolates. Overall, B0-1165 had in vitro properties similar to those of other monobactams currently available or under investigation.