Antimicrobial activity of ethanolic extracts of Canavalia ensiformis (L.) DC and a Psidium guajava (L.) with Bidens pilosa (L.) combination against four Salmonella typhi strains

Abstract

Typhoid is a major global enteric burden in low and middle income countries that has been aggravated by emergence of resistant Salmonella typhi strains, its causative agent, with an increasing resistance to fluoroquinolones. The search for more effective, affordable and easily available drugs from sources such as medicinal plants has become a necessary to combat or reduce the challenge. In addition to other medicinal plants such as Canavalia ensiformis (L).DC, ethno-medicine surveys have shown that Psidium guajava L and Bidens pilosa, as well as their combination are frequently used in the management of typhoid in African communities. The purpose of this study therefore was to determine the antimicrobial activity of the of Canavalia ensiformis(L).DC ethanol leaf extract, and the combination of Bidens pilosa L with Psidium guajava L ethanol leaf extract against non-resistant, Multidrug resistant(MDR), MDR- ciprofloxacin susceptible and MDR-ciprofloxacin resistant strains of Salmonella typhi isolates. Pathogenic clinical isolates were used to give a vivid representation of the antimicrobial activity. Agar well diffusion on Mueller Hinton agar was used to determine the extent to which each extract inhibits each strain, broth dilution method was used to determine MIC, and streaking of the components of test tubes that showed no growth in the MIC test tubes was aseptically done to determine MBC of the active extract. It was found that Canavalia ensiformis leaf extract had no activity, the combination of Psidium guajava with Bidens pilosa had good antibacterial activity against all strains with the highest inhibition zone of 20.33±0.58mm against the susceptible strain, the lowest MIC of 25mg/ml and was found to be bactericidal to all strains with the lowest MBC of 50mg/ml. The extent of inhibition was found to reduce with increase in pattern of resistance and a statistically significant effect of the resistance pattern on the inhibition activity was realised (p<0.0001) (appendix II). The activity of this combination however was lower than the individual activity of Psidium guajava, but was higher than the individual activity of Bidens pilosa that did not show any activity on all strains. Conclusively, results from this study show that the combination of Psidium guajava L with Bidens pilosa L ethanol leaf extract has good antimicrobial activity against the four Salmonella tyhi strains that were used, with the ability to inhibit their growth and also kill the bacteria at certain concentrations while Canavalia ensiformis (L).DC leaf extract has no activity on any of xithe strains. This combination could thus be a possible source of compounds for antibiotics against Salmonella typhi strains.