[Activity of ticarcillin combined with different concentrations of clavulanic acid on 137 Gram-negative bacilli resistant to ticarcillin]

The MIC of ticarcillin exclusively or joined with 3 concentrations of clavulanic acid: (2, 4 and 8 mg/l) was determined by agar dilution in relation to 137 bacilli resistant to ticarcillin (MIC greater than or equal to 256 mg/l) detected between 1985 and 1986 in the Bellevue Hospital in Saint-Etienne. We could study 26 Escherichia coli, 30 Klebsiella, 28 Enterobacter, 36 Serratia and 17 Pseudomonas aeruginosa. The concentration of 2 mg/l of clavulanic acid allows to lower the MIC of ticarcillin over the very large majority of strains of Escherichia coli and Klebsiella resistant to ticarcillin. In those conditions, ticarcillin becomes more active than piperacillin over those species. The concentration of 4 and 8 mg/l of clavulanic acid doesn't bring any real advantage to those bacilli. Moreover the concentrations of 2, 4 and 8 mg/l slightly change the MIC of ticarcillin on the strains of Serratia, Enterobacter and Pseudomonas aeruginosa.