In vitro evaluation of U63196-E (AC-1370): antimicrobial activity, beta-lactamase stability, and beta-lactamase inhibition

BMY-28100, a new oral cephalosporin: antimicrobial activity against nearly 7,000 recent clinical isolates, comparative potency with other oral agents, and activity against beta-lactamase producing isolates

The antimicrobial activity of BMY-28100 was tested against approximately 7,000 bacterial pathogens in a multicenter, multiphased collaborative investigation. The BMY-28100 spectrum and antimicrobial potency was most similar to that of cefaclor and superior to that of cephalexin among currently available cephalosporins. Species that had greater than or equal to 90% of clinical strains inhibited by BMY-28100 (less than or equal to 8.0 micrograms/ml) were: Citrobacter diversus, Escherichia coli, Klebsiella spp., Proteus mirabilis, Salmonella spp., Branhamella catarrhalis, Haemophilus influenzae, Neisseria gonorrhoeae, N. meningitidis, methicillin-susceptible Staphylococcus supp., Streptococcus pneumoniae, S. pyogenes, S. agalactiae, S. bovis, serogroup C and G streptococci, Listeria monocytogenes and gm-positive anaerobes. BMY-28100 inhibited 9% more of the 6286 fresh clinical isolates at less than or equal to 8.0 micrograms/ml than cefaclor at the same concentration. BMY-28100 was generally bactericidal, but MICs for some species were markedly increased when an inoculum concentration of 10(7) CFU/ml was used. Strains producing plasmid-mediated beta-lactamases (TEM, OXA, SHV, HMS) were susceptible to BMY-28100, cefaclor, and cefuroxime. BMY-28100 was less active against strains producing chromosomal-mediated beta-lactamases (Types I and IV). BMY-28100 was not hydrolyzed significantly by the tested plasmid-mediated beta-lactamases, but was destroyed by Type I cephalosporinases and Klebsiella K1 enzymes.

In vitro comparative antimicrobial activity of cefpimizole against clinical isolates from five medical centers

Cefpimizole was compared with cefoperazone and cefotaxime against 6,599 clinical bacterial isolates from five medical centers. Cefoperazone and cefotaxime were both more active and provided a greater spectrum of antimicrobial coverage than cefpimizole. Some of the cefpimizole minimum concentrations inhibiting 50% of tested strains were as follows: Citrobacter freundii and Enterobacter cloacae, 16 micrograms/ml; Escherichia coli and Klebsiella pneumoniae, 2.0 micrograms/ml; Proteus mirabilis, 1.0 microgram/ml; Pseudomonas aeruginosa, 16 micrograms/ml; Staphylococcus spp., 32 micrograms/ml; and the enterococci, greater than 32 micrograms/ml.

In vitro antimicrobial susceptibility testing using 30 microG and 75 microG U63196-E (cefpimizole AC-1370) disks

U63196-E, a new cephalosporin, was evaluated for its antimicrobial spectrum and its application to standardized in vitro susceptibility test methods. The proposed criteria for the 75-micrograms U63196-E disk are greater than or equal to 18 mm (less than or equal to 16 micrograms/ml) = susceptible and less than or equal to 14 mm (greater than 32 micrograms/ml) = resistant. These limits are preferred to the 30 micrograms disk and produce only 4.2% major and very major interpretive errors. Previously published interpretive criteria for the 75 micrograms cefoperazone disk were confirmed.