In vitro activity of RU 29246, the active compound of the cephalosporin prodrug ester HR 916.

The in vitro activity of RU 29246 was compared with those of other agents against 536 recent clinical isolates. The MICs of RU 29246 for 90% of members of the family Enterobacteriaceae tested (MIC90s) were less than 2 micrograms/ml except those for Morganella spp. (16 micrograms/ml) and Proteus spp. (8 micrograms/ml). RU 29246 was active against Staphylococcus aureus (MIC90, < or = 8 micrograms/ml) and against Staphylococcus saprophyticus and coagulase-negative staphylococci (MIC90s, < or = 2 micrograms/ml). Streptococci and Neisseria gonorrhoeae were highly susceptible to RU 29246, and the activity of the agent against isolates of Streptococcus pneumoniae (MIC90, < or = 0.5 micrograms/ml), Haemophilus influenzae (MIC90, < or = 2 micrograms/ml), and Moraxella catarrhalis (MIC90, < or = 2 micrograms/ml) was comparable to those of the other cephalosporins tested. RU 29246 was insusceptible to hydrolysis by the common plasmid-mediated beta-lactamases (TEM-1 and SHV-1). However, hydrolysis by the new extended-spectrum beta-lactamases (TEM-3, TEM-5, and TEM-9) was detected. Results of the study suggested that RU 29246 should be investigated clinically for use in the treatment of a wide range of infections.