Antibacterial Activities and Phytochemical Screening of Crude Extracts from Kenyan Macaranga Species Towards MDR Phenotypes Expressing Efflux Pumps

Introduction: Macaranga species are traditionally used for the treatment and management of coughing, fungal infection, and wounds. In this study, the phytochemical screening and antibacterial activities of nine crude extracts from Macaranga conglomerata, Macaranga kilimandscharica and Macaranga capensis were determined against 13 bacterial strains expressing multi-drug resistance (MDR) phenotypes. Methods: Phytochemical screening of the extracts were carried out according to the standard methods, while the iodonitrotetrazolium chloride (INT) colorimetric assay was used to determine the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of the plants extracts. Results: Flavonoids, terpenoids, saponins and coumarins were the major secondary metabolites found in all the plant extracts. The results of antibacterial studies revealed that all the plant extracts displayed good activities with MIC values ranging from 4 – 128 µg/mL against the tested micro-organisms. Most of the extracts exhibited a bactericidal effect against E. coli, E. aerogenes, K. pneumoniae, P. stuartii, P. aeruginosa, and S. aureus with MBC/MIC ratio ≤ 4. In the presence of efflux pump inhibitor (PaβN), the inhibition potency of all the crude extracts against the tested bacterial strains were substantially enhanced. It is worth noting that the activities of MKL, MCL, and MCR towards P. stuartii (NEA16), E. aerogenes (ATCC13048), and K. pneumoniae (KP55), respectively were improved by more than 8-fold in the presence of PAβN. Conclusion: The findings of this study indicated the possibility of using all the tested plant extracts as a source of therapeutic agents in the fight against multi-drug resistant bacteria.