Abstract:
Medicinal plants have been used as traditional treatments for various human diseases for many
years and they are still widely practiced throughout the world. Due to long history of practice,
medicinal plants have become an integral part of the Ethiopian culture. Thus the aim of this
study was to evaluate the antibacterial activities of Vernonia auriculifera and Buddleja
polystachya leaf extracts and their synergistic effect against some selected human pathogenic
bacteria; namely: Staphylococcus aureus (ATCC 43300), Staphylococcus aureus(clinical
isolate) Escherichia coli(ATCC 35218), Escherichia coli (clinical isolates), Pseudomonas
aeruginosa (ATCC 27853) and Salmonella typhimurium (ATCC 1333). Ethanol, methanol and
n-hexane crude extracts of V.auriculifera, B.polystachiya and mixture of the two plant
respective of each solvent were evaluated against tested pathogenic bacteria using agar well
diffusion method; the inhibition zones were recorded in millimeters. Gentamycin was used as
positive control, while dimethyl sulfoxide (DMSO) was served as negative control. The
minimum inhibitory concentration (MIC) of the plant extracts against test bacteria were
evaluated using two fold broth dilution methods and then Minimum bactericidal concentration
(MBC) were determined by sub-culturing the test dilutions from MIC tubes on to fresh Muller
Hinton Agar (MHA) plates incubating at 37°C for 24h. Ethanol and methanol crude extracts of
V.auriculifera showed excellent antibacterial activities against S.typhimurium, S. aureus
(ATCC 43300) and S.aureus (clinical isolate). Maximum antibacterial inhibition zone was
observed on methanol extracts of synergism against S. typhimurium (ATCC 1333) (31.00±1.73
mm) while, minimum inhibition zone was observed on methanol extract of B.polystachiya
against E.coli (ATCC 35218) (5.67±0.57). MIC and MBC values of the crude extracts of
V.auriculifera, B.polystachiya, and mixture of them lies between (3.125%-12.5%) and (6.25%-
25%) respectively. Thus, the present study support the claim along with the development of
new antibacterial drugs from both plants. Therefore, this study Provide recommendation as
further study is required on clinical isolates to use this extract as antibiotics.
