Fifty-five strains of Pseudomonas aeruginosa were isolated from urine, sputum, and pus in PNU hospital, and submitted to the synergistic activity test of streptomycin(STM) combined with cefotaxime(CFT) or piperacillin(PIPC).
The minimal inhibitory concentrations(MICs) of each drug and drugs combined in various ratios were measured by checkerboard dilution method. The synergism was determined through calculating the fractional inhibitory concentration index(FICI).
1. MICs of streptomycin against 55 tested strains were distributed from 0.5μg/ml to 512μg/ml.
2. Among the drugs of β-lactam, MICs of cefotaxime and piperacillin were distrbuted from 0.5 to 512μg/ml, respectively.
3. In 55 strains tested were inhibited synergistically by the two drug combination(STM-CFT) were 30 strains(54.54%) and 13 strains(23.64%) showed additive response to STM and CFT, while 12 strains(21.82%) showed antagonistic response.
4. In 55 strains tested were inhibited synergistically by the two drug combination(STM-PIPC) were 35 strains963.64%) and 8 strains(14.54%) showed additive response to STM and PIPC, while 12 strains(21.82%) showed antagonistic response.
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