In vitro activity of BRL 17421 against Haemophilus influenzae, Neisseria gonorrhoeae, and Branhamella catarrhalis.

BRL 17421, a novel beta-lactam antibiotic, was tested in vitro against fastidious gram-negative bacteria and compared with amoxicillin and amoxicillin plus clavulanic acid. The compound showed good activity against Haemophilus influenzae (range of minimal inhibitory concentrations, 0.2 to 1 microgram/ml), Neisseria gonorrhoeae (0.007 to 0.5 microgram/ml), and Branhamella catarrhalis (0.03 to 0.1 microgram/ml). BRL 17421 exhibited excellent stability against the TEM-type beta-lactamase of H. influenzae and N. gonorrhoeae, and its activity was little affected by inoculum size. Minimal lethal concentrations of BRL 17421 for 10(7) colony-forming units of H. influenzae ranged between 0.5 and 4 micrograms/ml.