Potential antibacterial activity of berberine against multi drug resistant enterovirulent Escherichia coli isolated from yaks (Poephagus grunniens) with haemorrhagic diarrhoea

Objective: To evaluate the antimicrobial efficacy of berberine. a plant alkaloid. Methods: Five multi drug resistant (MDR) STEC/EPEC and five MDR ETEC isolates from yaks with haemorrhagic diarrhoea were selected for the study. Antibacterial activity of berberine was evaluated by broth dilution and disc diffusion methods. The binding kinetics of berberine to DNA and protein was also enumerated. Results: For both categories of enterovirulent Escherichia coli (E. coli) isolates, berberine displayed the antibacterial effect in a dose dependent manner. The MIC50 of berberine chloride for STEC/EPEC isolates varied from 2.07 mu M to 3.6 mu m with a mean of (2.95 +/- 0.33) mu M where as for ETEC strains it varied from 1.75 to 1.96 mu M with a mean of (1.87 +/- 0.03) mu M. Berberine bind more tightly with double helix DNA with Bmax and Kd of (24.68 +/- 2.62) and (357.8 +/- 57.8), respectively. Berberine reacted with protein in comparatively loose manner with Bmax and Kd of (18.9 +/- 3.83) and (286.2 +/- 113.6), respectively. Conclusions: The results indicate clearly that berberine may serve as a good antibacterial against multi drug resistant E. coli.