Extracts of carrot, garlic and ginger as selective agents in basal bacteriological media were carried out on Staphylococcus aureus ATCC 15313, Listeria monocytogenes ATCC 2522,Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853 using a standard method. Ethanolic extracts, aqueous cold and hot extracts of the experimental plant products were made at the concentration of 200 mg/ml (2 g/10 ml). The ethanolic extracts inhibited the growth of all the test bacterial isolates. The cold aqueous extracts of garlic had inhibitory effects on the S. aureus and L. monocytogenes bacterial isolates but selectively allowed the growth of E. coli. The hot aqueous extract of ginger had no effect on any of the test bacteria. The hot garlic extract selectively allowed the growth of L. monocytogenes and E. coli. Phytochemical analysis of the carrots, garlic and ginger contained saponnin, resins, alkaloids, flavonoids, steroids and terpenes in varied proportions. We assume these products may have influenced the actions of the extracts on the test organisms. The results of this preliminary study suggest that aqueous extracts of carrots, garlic and ginger when incorporated in appropriate concentrations can serve as alternative selective agents in bacteriological culture media for bacterial isolation from highly contaminated biological specimens or separation of mixed cultures of bacteria in the laboratory.
Key words: Carrot, garlic, ginger, selective agents, bacteria, culture media
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