Antibacterial activity of ciprofloxacin and trimethoprim, alone and in combination, against Vibrio cholerae O1 biotype E1 Tor serotype Ogawa isolates

In this communication, the ciprofloxacin-trimethoprim (Cp-Tm) combination showed synergistic (Fractional Inhibitory Concentration, FIC index 0.399) and additive (FIC index 0.665-0.83) effects against Vibrio cholerae O1 biotype El Tor serotype Ogawa isolates having Cp MICs 10 μg/ml and Cp 0.66 μg/ml, respectively, following agar dilution checkerboard method. The time-kill study results demonstrated synergy between Cp and Tm against both groups of isolates providing 2.04 log₁₀ (for strain with Cp MIC 0.66 μg/ml) and 3.12 log₁₀ (for strain with Cp MIC 10 μg/ml) decreases in CFU/ml between the combination and its most active compound. Thus, the findings of the present study suggest an introduction of Cp-Tm combination treatment regimen against drug resistant cholera and this in turn will help in combating the drug resistance of V. cholerae O1 biotype El Tor serotype Ogawa.