Tanzania Veterinary Association Proceedings Vol. 38 (2020)
Resistance against synthetic antimicrobial agents is one of the major global public health
challenges that compel scientists to search for alternatives including those of plants origin.
Staphylococcus aureus and Escherichia coli are bacteria responsible for a variety of infections
and diseases that causes significant morbidity and mortality in humans and animals. E. coli is
widely distributed in nature and commonly found in lower gastro intestinal tracts of most warm-
blooded animals associated with urinary tract infections and enterocolitis in humans and
colibacillosis in poultry. This study was carried out to investigate antimicrobial activity of
methanolic leaf extracts of Bidens pilosa against S. aureus and E. coli. Agar well diffusion
method was used to assess antimicrobial activity of the leaf extracts at 20%, 50% and 70%
concentrations respectively based on measured zone of inhibition. The leaf extracts of Bidens
pilosa produced significant zone of inhibition indicating its antimicrobial activity against E. coli
and S. aureus. The antimicrobial activity was demonstrated in all concentrations however, the
highest zone of inhibition (18.5mm and 32mm) for E. coli and S. aureus respectively was at 70%
concentration. The results shows that Bidens pilosa leaf extracts have antimicrobial activity
against the tested bacteria and have the potential for further development including identification
of active components that can be tested for treatment of E. coli and S. aureus associated
conditions.
Key words: antimicrobial resistance, medicinal-plants, natural-products, blackjack, E. coli, S.
aureus