Antibacterial activity and phytochemical screening of some medicinal plant extracts against bacteria isolated from food materials sold in Keffi, Nasarawa State, Nigeria

Phytochemical analysis of ethanol and aqueous extracts of the leaves and bark of Bidens plasa and Brilliantasia patula plant were carried out using standard technique. The plants parts were extracted through cold maceration technique. Bacteria were isolated using standard microbiology methods. Antibacterial activity of the extracts was carried out using agar well diffusion technique. Results of the phytochemical analysis revealed flavonoids, phenols, alkaloid, tannins, steroids, saponins, anthraquinone, reducing sugar, terpenes and glycosides were present in the plant extracts. The extracts were tested against Staphylococcus aureus, Escherichia coli, Klebsiella spp, Salmonella spp and P. aeruginosa isolated from tomato, vegetables and dry fish. The aqueous leaves extract of Bidens plasa inhibited all the test isolates at 50.0 mg and 25.0 mg. The ethanol leaves extracts of Bidens plasa had more antibacterial activity against the test bacteria. The ranges of inhibition zone of the test bacteria were E. coli had 14.0±0.42 mm at 50.0 mg, 11.00±2.00 mm at 25.0mg and 7.00±0.10 mm at 12.5 mg; Klebsiella spp with 13.03±0.32 mm at 50.0 mg and 10.0±3.00 mm at 25.0mg respectively. The bark of extract of Brilliantasia patula had more antibacterial activity in various amount of the extract ranging from 50mg – 12.5mg against the test bacteria. The range of inhibition zone of the test bacteria were E. coli had 13.0±0.21 mm at 50.0 mg, 7.0±1.00 mm at 25.0mg and 5.00±0.11 mm at 12.5 mg and Klebsiella spp with 10.00±1.00 at 50.0 mg and 6.00±0.01 mm at 25.0 mg. The antimicrobial activity demonstrated by these plant extracts on food borne pathogens indicated the preservative potentials these extracts possess in controlling the bacteria growth.