Antibacterial Activity and Synergism of Sapium ellipticum (Hochst.) Pax and Harungana madagascariensis (Lam. Ex Poir) Stem bark Extract against Methicillin Resistant Staphylococcus aureusarscariensis (Lam. Ex Poir) Stem Bark Extracts Against Methicillin resistant Staphylococcus aureus

Abstract

Background: The increase in infections involving anti-microbial resistant (AMR) bacteria like Methicillin-resistant Staphylococcus aureus (MRSA) has limited therapeutic options and has been consistently found to be among the top causes of threats to global health. Combining antibacterial agents and/or medicinal plants has minimized this AMR crisis worldwide.

Aim: This study aimed to investigate in vitro synergistic antibacterial activity of Sapium ellipticum (Hochst.) Pax and Harungana madagascariensis (Lam. Ex Poir) stem bark extracts against Methicillin resistant Staphylococcus aureus (MRSA).

Methods: The MRSA clinical isolates were identified phenotypically and genotypically before being used as test microorganisms. Stem bark plant extracts of S. ellipticum and H. madagascariensis were prepared using methanol and dichloromethane solvents. Screening of antibacterial activities of plant extracts was done using the agar-well diffusion method, and minimum inhibitory concentration (MIC) determination was done by serial microdilution technique.

Results: The MIC for individual extracts ranged from 1.56 - 6.25 mg/mL, while MIC for combined extracts ranged from 0.2 - 0.8 mg/mL. Combined extracts were significantly more active than individual extracts. The study discovered synergistic interaction when combining methanol or dichloromethane extracts of S. ellipticum and H. madagascariensis against MRSA isolates. The suitable combination ratio for methanol and dichloromethane extracts was 1:1, though a 3:1 ratio also resulted in synergistic interaction in the methanolic combination. 

Conclusion: The differences in MIC range between the individual and combined extracts might be attributed to the concentration and composition of the extracts. These results provide promising information for using methanol or dichloromethane crude extracts of S. ellipticum and H. madagarscariensis stem barks in synergism against MRSA isolates.