In vitro studies of moxalactam (LY127935), a new beta-lactam antibiotic with significant activity against gram-negative bacteria.

Moxalactam (LY127935) is a new beta-lactam antibiotic which is chemically related to the cephalosporins. The agent is highly active against the Enterobacteriaceae, with most organisms sensitive to 0.1 mcg/ml or less. It is also active at low concentration against gentamicin-resistant strains of Providencia and Serratia. Minimal inhibitory concentrations of moxalactam for Pseudomonas aeruginosa are approximately four-fold lower than those of carbenicillin for the same isolates. It is highly active against Hemophilus influenzae, including ampicillin-resistant strains, with all strains tested sensitive to 0.1 mcg/ml or less. The majority of strains of Neisseria gonorrheae and Neisseria meningitidis are sensitive to 0.1 mcg/ml or less. Moxalactam is more active against Bacteroides fragilis than cefoxitin. However, activity of moxalactam against gram-positive cocci was uniformly less than cephalothin and other cephalosporins tested. Little effect of inoculum size was observed with moxalactam except for particular strains of gram-negative bacilli. The drug was found to be 40-43% bound to human serum proteins.