In vitro antibacterial activity of biapenem, a new carbapenem antibiotic

Abstract

The in vitro activity of new carbapanem, biapenem (BIPM) was studied in comparison with impenem (IPM) and ceftazidime (CAZ). BIPM showed good activity against a broad antibacterial spectrum of gram-positive, gram-negative clinical isolates including Pseudomonas aeruginosa, and anaerobes.
BIPM was two-to fourfold less active than IPM against gram-positive cocci. BIPM was more active than IPM against gram-negative bacteria, inhibiting all Enterobacteriaceae, except for 12% of Proteus mirabilis, 7% of Proteus vulgaris, 8% of Morganella morganii, and 50% of Serratia marcescensisolates, at a concentration of≤1.56μg/ml. BIPM inhibited CAZ-resistant the genera Citrobacter and Enterobacter at≤0.39 μg/ml. BIPM also showed a high activity against Pseudomonas aeruginosa, its activity was two-hold higher than that of IPM. BIPM did not inhibit most methicillin-resistant staphylococci, Enterococcus faecium, and Xanthomonas maltophilia strains, as did not IPM and CAZ. Bactericidal activity of BIPMagainst gram-positive and gram-negative bacteria was confirmed though counting viable cells and determining the minimum bactericidal concentrations.
BIPM was not hydrolyzed by various types of β-lactamase. Xanthomonas maltophilia L-1 type β-lactamase hydrolyzed BIPM, albeit at approximately one half the rate than IPM was hydrolyzed.
Outer membrane permeability of Pseudomonas aeruginosa to BIPM was determined by Zimmermann and Rosselet method. The permeability coefficients of BIPM at 50μM and 100μM, were 2.04×10^-6 and 1.32×10^-6 cm/s, respectively.