In-vitro assessment of the antimicrobial activity of a combination of methanolic extracts of Acacia nilotica and Ziziphus mauritiana against streptococcus pneumoniae

Abstract

Background: In Uganda, Streptococcus pneumoniae is one of the most important causes of morbidity, with a prevalence of 45.9%. Many communities are currently resorting to traditional medicine for primary health care. Plants such as a combination of Acacia nilotica and Ziziphus mauritiana have been used traditionally to treat upper respiratory tract infections like pneumonia, but no study has been made on the use of these plants in combination. Aim: To determine the antibacterial activity of a combination of methanolic leaf extracts of Acacia nilotica and Ziziphus mauritiana against Streptococcus pneumoniae. Methods: This was an experimental study involving collection of quantitative data. Methanolic leave extracts were obtained from the plant samples following a modified procedure. Well diffusion technique was used to assess the antibacterial activity. Concentrations of 25, 50, 100 and 200 mg/ml were assessed. Extract combinations of 25:75, 50:50, and 75:25 (Acacia: Ziziphus) was also assessed. Zones of inhibition were measured in mm using a caliper. Data analysis: Collected data was analyzed using Graph pad software package and expressed as mean + standard deviation of mean. The differences between means were compared using pair wise analysis of variance performed at 95% confidence interval and their corresponding p-value reported and MIC of the extracts determined by graphical method. Results: The MIC Acacia nilotica extract was 5.384 mg/ml, while that of Ziziphus mauritiana was 9.144 mg/ml. The inhibitory effect of Acacia nilotica were generally higher than that of Ziziphus in all concentrations (25, 50, 100 and 200 mg/mL). The MIC for Acacia nilotica in combination was 32.261 mg/ml and that of Ziziphus mauritiana in combination was 10.950 mg/ml. The FICI reported was 7.188, indicative of antagonism. Conclusion: The individual plant extracts had better anti- streptococcal activity than the extracts in combination which agrees with the null hypothesis. Key words: Streptococcus pneumonia, antibacterial, Acacia nilotica and Ziziphus mauritiana