Comparative in vitro studies on the beta-lactamase-inhibiting effect of clavulanic acid and sulbactam on ampicillin-resistant Enterobacteriaceae.
Clavulanic acid and sulbactam alone are ineffective against Pseudomonas and enterococci. Staphylococci and Enterobacteriaceae are inhibited by high concentrations not attainable under clinical conditions. Strains of Acinetobacter, especially A. lwoffii are susceptible to clavulanic acid and highly susceptible to sulbactam. The ampicillin/sulbactam combination is superior to ampicillin/clavulanic acid against Citrobacter freundii, Enterobacter spp. and Morganella morganii. The latter combination is superior against Klebsiella spp. and Escherichia coli. Antagonistic effects are more frequent with the clavulanic acid combination (Enterobacter spp. and C. freundii) but are rarely observed with the sulbactam combination (Providencia spp. and P. rettgeri).
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Institute for Medical Microbiology and Clinical Chemistry (Laboratory Dr Gärtner), Hoyerstrasse 51, D-88250 Weingarten, Germany.