Despite the medicinal importance of Balanites aegyptiaca (L.) Del, Stevia rebaudiana (Bert.) Bertoni, Tylophora indica (Burm.f.) Merrill and Cassia sophera (Linn.), the antimicrobial potential of these plants has not been explored extensively, especially those of Cassia sophera.

Both aqueous and alcoholic extracts of various parts of respective plants, and their in vitro raised calli were tested for antimicrobial activity by agar well diffusion method against a range of gram-positive and gram-negative bacteria and several fungal species. The calli of Balanites aegyptiaca and Tylophora indica were only tested as calli of Stevia rebaudiana and Cassia sophera could not be generated due to failure of regeneration in our laboratory. The extracts were also tested against genetically characterized bacterial isolates harboring bla (antibiotics resistance) genes. Minimal inhibitory concentrations (MICs) of the extracts were determined by broth microdilution method.

The extracts from all the four plants showed significant antibacterial activity against gram-negative bacteria, including, Salmonella typhi, Salmonella paratyphi A, Escherichia coli, Klebsiella species, Proteus vulgaris, Citrobacter spp., Salmonella typhimurium, Pseudomonas aeruginosa and Vibrio cholerae. Among all the tested plants, only B. aegyptiaca showed significant antibacterial activity against the tested gram-negative bacteria harboring bla genes including, Escherichia coli (bla ampC), Klebsiella spp. (bla CTX-M), Klebsiella spp. (bla SHV), Escherichia coli (bla SHV+CTXM) and Citrobacter spp. (bla ampC+SHV). Extracts of B. aegyptiaca and S. rebaudiana also showed activity against grampositive bacteria whereas the extracts from Tylophora indica and Cassia sophera did not. Extracts of Balanites aegyptiaca, Tylophora indica, and Stevia rebaudiana demonstrated potential antifungal activity whereas extracts of Cassia sophera din not demonstrate the antifungal activity.

This is among the premier reports describing the antimicrobial potential, especially through calli extracts, of Tylophora indica (Burm.f.) Merrill and Balanites aegyptiaca (L.) Del and in particular against gram-negative bacteria harboring bla genes. This is also a premier report looking extensively for the antimicrobial potential in Cassia sophera.