Antibacterial and antibiotic-potentiation activity of <i>Coffea arabica</i> and six other Cameroonian edible plants against multidrug-resistant phenotypes

Abstract

Background: Medicinal plants have always played an important role in human health. Many plants are traditionally used as drugs against microbial infections. In this study, a panel of seven methanol extracts from Cameroonian edible was assessed for their antibacterial potentiality against multidrug-resistant Gram-positive and Gram-negative bacteria.

Methods: The microdilution technique using a 96-well plate was used to assess the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of the crude extracts, as well as their potential to improve the antimicrobial activity of certain families of antibiotics. Phytochemical screening of the extracts was carried out according to the standard methods.

Results: The most detected classes of pharmaceuticals were tannins, triterpenes, polyphenols, and steroids. Coffea arabica bark extract inhibited all 20 tested MDR bacteria strains; Coffea arabica leaf and seeds extracts, Adansonia digitata bark extract, Sechium edule leaf extract, all inhibited 95% (19/20) of the strains tested, Beilschmeidia louisii stem extract inhibited the growth of 85% (17/20) of the tested bacteria, while Hyphaene therbaica displayed 70% (14/20) bacterial inhibition. The MIC values of the plant extracts ranged from 256 to 2048 μg/mL. However, the best MIC value (256 μg/mL) was obtained with B. louisii stem extract against E. coli AG102 and S. aureus MRSA12. The leaf extract of S. edule improved the anti-bacterial activities of kanamycin, tetracycline, and Cloxacillin against the MDR strain P. stuartii 29916 by up to 16 times; furthermore, this extract improved the antibacterial effect of tetracycline, Cloxacillin, kanamycin, and doxycycline by 16 folds against the MDR strain E. coli AG100ATET; the bark extract of C. arabica improved the activities of ofloxacin, chloramphenicol the activities of ofloxacin, chloramphenicol, and doxycycline toward all the tested MDR Gram positive and Gram-negative bacteria with improvement activity factor (IAF) ranging from 2 to 16, while the leaf extract of B. louisii increased up to 8-fold the activity of Cloxacillin against P. aeruginosa PA 124.

Conclusion: Coffea arabica, Adansonia digitata, Sechium edule, and Beilschmeidia louisii are the explorable sources of antibacterial agents usable alone or in combination with conventional antibiotics to tackle diseases caused by resistant bacterial phenotypes.