Post antibiotic effect of gentamicin in combination with cephradine, cefotaxime on pseudomonas aeruginosa

ABSTRACT

The post-antibiotic effect [PAE] of gentamicin [Gm] alone and in combination with cephradine [Cef] or cefotaxime [Ctx] was studied for five isolates of Pseudomonas aeruginosa. Cultures of Pseudomonas aeruginosa isolates were incubated with cephradine or cefotaxime [4 MIC] for one hour. Two different concentrations of gentamicin [0.5 and 1.0 MIC] were then added. Incubation of the combinations continued for one more hour. The antibiotics were eliminated by dilution. The post-antibiotic effects produced by the drugs in combination were longer than the sum of the individual effects of the drugs when they were used alone. A synergic post-antibiotic effect was also found when Pseudomonas aeruginosa strain No. 1 simultaneously exposed to gentamicin combination with cephradine or cefotaxime for 2 hours