Antibiotic interaction of amoxycillin and clavulanic acid against 132 beta-lactamase positive Haemophilus isolates: a comparison with some other oral agents.
We studied the specific beta-lactamase inhibitory activity of clavulanic acid in association with amoxycillin against 132 beta-lactamase producing Haemophilus isolates. Inhibitory synergy between amoxycillin and clavulanic acid (ratio 2:1) was found in 131/132, partial synergy or antagonism in none; bactericidal synergy was found in 124/131, partial synergy in 4 and antagonism in 1. In comparison, inhibitory synergy between trimethoprim and sulphamethoxazole (ratio 1:19) was found in only 39/104 beta-lactamase positive strains, partial synergy in 42 and antagonism in 3 and bactericidal synergy in 18/104, partial synergy in 8 and antagonism in 3. The amoxycillin-clavulanic acid combination expressed significantly (P less than 0.001) more frequent synergy, at both inhibitory and bactericidal levels, than the trimethoprim-sulphamethoxazole combination. The synergy of amoxycillin-clavulanic acid resulted in a significant decrease of MIC90 (greater than or equal to 32.0-2.0 mg/l) and MBC90 (greater than or equal to 32.0-4.0 mg/l) of amoxycillin; the synergy of trimethoprim-sulphamethoxazole resulted in a significant decrease of MIC90 (8.0-2.0 mg/l) of trimethoprim but did not change MBC90. The amoxycillin-clavulanic acid combination was also more active than cefaclor or erythromycin alone against the 132 beta-lactamase producing strains.
D000658:Amoxicillin / Q000494:pharmacology*; D019818:Clavulanic Acid; D002969:Clavulanic Acids / Q000494:pharmacology*; D004338:Drug Combinations / Q000494:pharmacology; D004357:Drug Synergism; D006193:Haemophilus influenzae / Q000145:classification / Q000187:drug effects* / Q000201:enzymology; D006801:Humans; D008826:Microbial Sensitivity Tests; D013420:Sulfamethoxazole / Q000494:pharmacology; D014295:Trimethoprim / Q000494:pharmacology; D015662:Trimethoprim, Sulfamethoxazole Drug Combination; D001618:beta-Lactamases / Q000378:metabolism
D002969:Clavulanic Acids; D004338:Drug Combinations; D019818:Clavulanic Acid; D000658:Amoxicillin; D015662:Trimethoprim, Sulfamethoxazole Drug Combination; D014295:Trimethoprim; D001618:beta-Lactamases; D013420:Sulfamethoxazole