Antibacterial and antibiotic-potentiating activities of nine Cameroonian medicinal plants against multidrug-resistant bacteria expressing active efflux pumps

Abstract

Background: In the last ten years, the resistance of Gram-negative and Gram-positive bacteria continuously increased. The present study was designed to evaluate the antibacterial and antibiotic-potentiating activities of nine Cameroonian medicinal plants: Cucumeropsis mannii, Lagenaria siceraria, Citrullus lanatus, Cucurbita moschata, Salix ledermannii, Gouania longispicata, Psychotria mapourioides, Conyza aethiopica and Conyza sumatrensis against resistant phenotypes. Methods: Liquid broth microdilution method was used for the determination of antibacterial activities, while standard methods were used for phytochemical screening to detect the major classes of secondary metabolites in the extracts. Results: The result of phytochemical screening revealed that the secondary metabolite classes were selectively detected in the extracts. The studied extracts showed antibacterial activities with minimum inhibitory concentrations (MIC) ranging from 64 to 1024 µg/mL on the tested strains. The Gouanea longispicata extract showed the greatest spectrum of action notably against 86.4% of the bacterial strains tested. The synergistic effects of the extracts and antibiotics observed varied from 20 to 60%. Salix ledermannii leaf extract in combination with cloxacilin and ciprofloxacin, showed the highest synergistic effects (60%) towards the tested pathogens. Conclusion: The present study provides information on the possible use of the tested Cameroonian medicinal plants in the control of bacterial infections, especially those caused by resistant phenotypes. It also indicates that extracts of Gouania longispicata and Salix ledermannii leaves can be used as natural modulators of antibiotic resistance to control MDR bacteria. Keywords. Antibacterial; antibiotic modifying activity; Cameroon; medicinal plants; multi-drug resistance.