Selective in Vitro Growth Inhibitory Effect of Withania Somnifera on Human Pathogenic Bacteria and Bifidobacteria

Antimicrobial activity of crude acetone extract from the aerial part of Withania somnifera was tested in vitro against six pathogenic bacteria viz., Bacillus cereus, B. subtilis, Staphylococcus epidermis, S. aureus, Streptococcus pneumoniae and S. pyogenes and five bifidobacteria viz., Bifidobacterium animalis, B. breve, B. catenulatum, B. infantis and B. longum evaluating its potential harmful effect on beneficial gastrointestinal microbiota using disk diffusion method. The results showed that pathogenic bacteria were significantly more susceptible to the extract of W. somnifera than bifidobacteria (average of diameters of inhibition zones 20.45 mm and 13.10 mm, respectively) at the concentration of 2 mg/disc. Among all bacteria tested, S. pneumoniae was the most sensitive, while B. animalis was the most resistant species. These results suggest W. somnifera as an effective antibacterial agent against human pathogenic bacteria with lowered harmful effect on bifidobacteria.