ABSTRACT
Background: Infectious diseases are the greatest challenge of the world. The main failure in the treatment of infectious diseases is development of antibiotic resistance by the infective agents. Combination drug therapy is proposed to be more successful to contain diseases. But before the selection of combination of antibiotics, it is important to determine interaction of such antibiotics. Two antibiotics may have either synergistic or antagonistic action. In this study it was designed to find out the Minimum Inhibitory Concentration (MIC), and Minimum Bactericidal Concentration (MBC), which is usually used for the quantitative assessment of bacterial sensitivity to antibiotics. Methods: Checkerboard titration in microtitre trays used for this assay, and Fractional Inhibitory Concentration (FIC) and Fractional Bactericidal Concentration (FBC) measured to identify the type of interaction between the two antibiotics. Cefsulodin (Cef) and Kanamycin (Kan) were used against Escherechia coli (Esch. coli) and Staphylococcus aureus (Staph. aureus) to determine the efficacy of these antibiotics in combination. Results: MIC of cefsulodin and kanamycin against Staph. aureus was 3.125 and 3.125 respectively. MIC of Cef for Esch. coli was 6.25 and for Kan 50. FIC for Staph. aureus was 1. FIC for Esch. coli was different in different antibiotic concentrations and the least value was 0.37. There was no bactericidal effect of these antibiotics in combination against these organisms. Conclusion: Combination of two drugs cefsulodin and kanamycin showed synergistic action against Esch. coli and additive against Staph. aureus. So combined drug therapy can be used for better treatment with low toxicity, broad spectrum activity, and prevent emergence of drug resistance organism.