Abstract
The present work was designed to investigate the antibacterial activities of methanol extracts from six Cameroonian edible plants and their synergistic effects with some commonly used antibiotics against multidrug-resistant (MDR) Gram-negative bacteria expressing active efflux pumps. The extracts were subjected to qualitative phytochemical screening and the microdilution broth method was used for antibacterial assays. The results of phytochemical tests indicate that all tested crude extracts contained polyphenols, flavonoids, triterpenes, and steroids. Extracts displayed selective antibacterial activities with the minimal inhibitory concentration (MIC) values ranging from 32 to 1024 μg/mL. The lowest MIC value (32 μg/mL) was recorded with Coula edulis extract against E. coli AG102 and K. pneumoniae K2 and with Mangifera indica bark extract against P. aeruginosa PA01 and Citrus sinensis extract against E. coli W3110 which also displayed the best MBC (256 μg/mL) value against E. coli ATCC8739. In combination with antibiotics, extracts from M. indica leaves showed synergistic effects with 75% (6/8) of the tested antibiotics against more than 80% of the tested bacteria. The findings of the present work indicate that the tested plants may be used alone or in combination in the treatment of bacterial infections including the multidrug-resistant bacteria.
Highlights
The discovery of antibiotics has inevitably fostered the development and emergence of resistances in bacteria, regardless of the mechanism of action of the antibiotic involved
The plant materials used in this work were collected in the period of March to April 2015 in two regions of Cameroon and included leaves and bark of M. indica; fruits, leaves, and bark of P. guajava; leaves and bark of P. americana collected at Koung-Khi division (West Region); leaves of C. sinensis and the fruits of C. sinensis collected at Menoua division (West Region); and nuts of C. edulis collected at Mungo division (Littoral Region)
The results showed that when combined with extracts, PAβN improves the activity of C. sinensis on 11/15 (73.33%) tested MDR strains
Summary
The discovery of antibiotics has inevitably fostered the development and emergence of resistances in bacteria, regardless of the mechanism of action of the antibiotic involved. With respect to efflux pumps, they provide a selfdefense mechanism by which antibiotics are actively removed from the cell This results in sublethal drug concentrations at the active site that in turn may predispose the organism to the development of high-level target-based resistance [5]. In this way, efflux pumps inevitably become targets for the research and/or development of new, less toxic, and effective molecules capable, alone or in combination with the usual antibiotics, of effectively fighting infections involving multidrug-resistant pathogens. The present work was designed to investigate the in vitro ability of methanol extracts from six Cameroonian edible plants
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