Activity of synergistic combination Amoxy-cassia against Salmonella

The object of this study was to formulate new, cost effective anti-microbial combination for Multi Drug Resistant (MDR) Salmonella enterica Serover Typhi (SEST) based on the synergistic activity of amoxicillin with the aqueous fruit solution of Cassia fistula (CFF), a medicinal plant found in Pakistan which when tested alone have weak antimicrobial activity against blood isolates of MDR SEST. MIC of MDR SEST for amoxicillin and CFF alone was 750 microg/ml and 3750 microg/ml. The MIC of amoxicillin in combination with CFF was 23.4-187.5 microg/ml and 0.37-1.56 microg/ml for MDR and MDS SEST respectively. Fractional Inhibitory Concentration Index (FICI) using chequer-board titration suggested synergism for 80% MDR and MDS SEST tested, no antagonism observed. Time kill kinetics showed difference > log2 in CFU of CFF having sub-lethal amoxicillin concentrations. This novel combination is named as Amoxy-cassia. In vivo it is found to be non toxic at 1 gm/body weight of mice.