Comparative in vitro activity of amoxycillin/clavulanate (augmentin), ceftazidime and ceftriaxone against hospital strains of gram-negative and -positive bacteria.

The in vitro antibacterial activities of amoxycillin/clavulanate (Augmentin), ceftazidime and ceftriaxone were compared against 330 gram-negative and gram-positive strains isolated from clinical specimens received at the King Abdulaziz University Hospital (KAUH) in Saudi Arabia. The antibacterial susceptibility was determinated by Stokes method and by the minimal inhibitory concentration (MIC) using an agar dilution method. Ceftazidime and ceftriaxone were the most active antibiotics, inhibiting 90% of the tested strains by obtainable serum concentrations. Augmentin, on the other hand, had much lower activity against most of the strains tested. Ceftazidime's activity was superior to that of ceftriaxone especially against Klebsiella spp., Enterobacter spp., Citrobacter diversus, indole positive Proteus, Providencia stuartii, Acinetobacter calcoaceticus and Pseudomonas aeruginosa. Ceftriaxone had better activity against Serratia orderefera, Morganella morganii and Staphylococcus aureus. Beta-lactamase stable cephalosporins are therefore a potential replacement for aminoglycosides in the antimicrobial therapy of serious Gram-negative infections and alternative agents in the treatment of some Gram-positive infections.