Comparative in-vitro activity of tigemonam, a new monobactam

The in-vitro activity against Gram-negative aerobic bacterial pathogens of a new oral monobactam, tigemonam, was compared with those of amoxycillin/clavulanic acid, aztreonam, cefaclor, ceftazidime, cefuroxime, ciprofloxacin, co-trimoxazole and gentamicin, by an agar-dilution method. Tigemonam inhibited 90% of strains tested of Escherichia coli, Klebsiella spp., Proteus spp., Salmonella spp., Haemophilus influenzae and Branhamella catarrhalis at concentrations of 0.25 mg/l or below. The MIC90 for Enterobacter spp. was 16 mg/l and for Citrobacter 4 mg/l. Pseudomonas aeruginosa was resistant to tigemonam but susceptible to aztreonam. In comparison with the other oral antibiotics tested, tigemonam was generally more active. Tigemonam showed minimal inoculum dependence, between 10(2) and 10(6) cfu per spot. It is concluded that tigemonam is a candidate for clinical trials in patients with infections caused by Gram-negative aerobes other than pseudomonas and acinetobacter.