In vitro activity of CGP 31523A, a broad-spectrum cephalosporin, in comparison with those of other agents

Penetration of moxifloxacin into bone evaluated by Monte Carlo simulation

Moxifloxacin is a fluoroquinolone with a broad spectrum of activity and good penetration into many tissues, including bone. Penetration of moxifloxacin into bone has not yet been studied using compartmental modeling techniques. Therefore, we determined the rate and extent of bone penetration by moxifloxacin and evaluated its pharmacodynamic profile in bone via Monte Carlo simulation. Twenty-four patients (10 males, 14 females) undergoing total hip replacement received 400 mg moxifloxacin orally 2 to 7 h prior to surgery. Blood and bone specimens were collected. Bone samples were pulverized under liquid nitrogen by a cryogenic mill, including an internal standard. Drug concentrations were analyzed by high-performance liquid chromatography. We used ADAPT II (results reported), NONMEM, and WinBUGS for pharmacokinetic analysis. Monte Carlo simulation was performed to reverse engineer the necessary area under the free concentration-time curve fAUC(SERUM)/MIC in serum and total AUC(BONE)/MIC in bone for a successful clinical or microbiological outcome. The median (10% to 90% percentile for between-subject variability) of the AUC in bone divided by the AUC in serum (AUC(BONE)/AUC(SERUM)) was 80% (51 to 126%) for cortical bone and 78% (42 to 144%) for cancellous bone. Equilibration between serum and bone was rapid. Moxifloxacin achieved robust (> or = 90%) probabilities of target attainment (PTAs) in serum, cortical bone, and cancellous bone up to MICs of < or = 0.375 mg/liter based on the targets fAUC(SERUM)/MIC > or = 40 and AUC(BONE)/MIC > or = 33. Moxifloxacin showed high bone concentrations and a rapid equilibrium between bone and serum. The favorable PTAs compared to the 90%-inhibitory MIC of Staphylococcus aureus warrant future clinical trials on the effectiveness of moxifloxacin in the treatment of bone infections.

Modulation of bacteriolysis by cooperative effects of penicillin-binding proteins 1a and 3 in Escherichia coli

Escherichia coli characteristically lyses upon treatment with most beta-lactam antimicrobial agents. In contrast, an investigational aminothiazole cephem, CGP 31523A, produced a new combination of antibacterial effects: it was highly bactericidal without causing cell wall degradation or lysis. Killing was associated with the formation of vacuolated filaments. Because the compound bound to penicillin-binding proteins (PBPs) 1a and 3, we investigated the role of PBP 3 in modulation of lysis caused by inhibition of PBP 1a. A temperature-sensitive mutant with a nonfunctional PBP 3 lysed when treated with CGP 31523A. The combination of a PBP 1 inhibitor (cefsulodin) and a PBP 3 inhibitor (aztreonam) also caused filamentation and death without lysis of wild-type cells over a narrow concentration range. We conclude that cooperative effects between PBPs in E. coli can lead to a dissociation of bacterial killing and lysis.