*1,2Baba, R. T., 1Oluboyo, B. O., 1Egbebi, A. H., 2Dangana, Z. A., 2Muhammad, Z. K.,
2Sowole, H. B., 2Sani, H. U., 2Yakubu, F., 3Aladodo, M., 2Babatunde, S. K., and 4Muhammed, T. O.
1Department of Medical Laboratory Science, College of Medicine and Health Sciences, Afe Babalola University, Ado-Ekiti, Nigeria
2Department of Medical Laboratory Science, Faculty of Health Sciences, Al-Hikmah University, Ilorin, Nigeria
3Department of Immunology, Faculty of Nursing and Allied Health Sciences, University of Abuja, Nigeria
4Department of Medical Laboratory Science, Faculty of Health Sciences, Elizade University, Ilara-Mokin, Ondo State, Nigeria
*Correspondence to: omotayo.rasheedat@gmail.com; rtbaba@alhikmah.edu.ng;
+2347065391534; +2349026144501
Abstract:
Background: Antibiotic resistance is currently a major global health concern. Multidrug-resistant (MDR) bacteria are emerging and spreading rapidly, threatening the ability to treat common infectious diseases such as urinary tract infection (UTI). The objective of this study is to determine the in vitro antimicrobial activities of two medicinal plants (Euphorbia hirta and Senna alata) and their synergistic effects with synthetic antibiotics.
Methodology: Aqueous and methanol extracts of the two plants were done using Soxhlet and cold maceration techniques. The antimicrobial activities of the extracts were assessed against selected clinical microbial isolates (Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Candida albicans) using the agar well diffusion while Kirby-Bauer disc diffusion was used for antimicrobial susceptibility testing of the isolates to some selected synthetic antibiotics as comparator. The minimum inhibitory concentration (MIC) of the extracts against the isolates was determined by the broth dilution method, and the minimum bactericidal concentration (MBC) was determined by sub-culturing samples from MIC tubes with no visible growth onto plain agar to determine the lowest concentration that resulted in 99.9% microbial kill. Synergy of synthetic anti- microbials and the plant extracts was determined by the modified disk diffusion test. Data were analyzed using SPSS version 25.0. The Student’s t-test was used to compare the mean zone diameter of inhibition (ZDI) of triplicate tests for each of the extract on the isolates, and p<0.05 was considered statistically significant.
Results: For E. hirta, methanol extracts exhibited significantly higher inhibitory activity (p<0.05) than aqueous extracts, particularly against P. aeruginosa (mean ZDI: 20.3±0.577mm vs 7.7±0.577mm) and C. albicans (mean ZDI: 20.7±1.155mm vs 6.0±0.577mm), with MIC values of 6.25mg/ml and 25.0mg/ml respectively. Similarly, for S. alata, methanol extracts exhibited higher inhibitory activity than aqueous extracts especially against S. aureus (mean ZDI: 21.3±1.528mm vs 6.0±1.155mm), but low inhibitory activity was observed against K. pneu- moniae (mean ZDI: 7.0±1.000mm vs 6.0±0.577mm). Synergy testing showed enhanced antimicrobial activities when aqueous and methanol extracts were combined with synthetic antibiotics especially imipenem, producing significantly larger mean ZDI against S. aureus (45.6±0.577mm vs 48.3±0.577mm for S. alata and 38.3
± 1.15mm vs 41.3±1.15mm for E. hirta). The combined extracts of the two plants also demonstrated significantly higher mean ZDI for methanol compared to aqueous extracts against E. coli (24.0±1.00mm vs 6.3±0.577mm), pneumoniae (20.3±0.577mm vs 6.7±1.155mm) and C. albicans (21.0±1.155mm vs 6.3±0.577mm).
Conclusion: The synergistic interactions between plant extracts and synthetic antibiotics in this study suggests a potential application in treatment of infections caused by antibiotic-resistant pathogens.
Keywords: Euphorbia hirta, Senna alata, Antibiotics, Antimicrobial activities, Synergistic.
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