Antibacterial activity of Terminalia glaucescens, Mangifera indica and Mitracarpus villosus on carbapenem-resistant enterobacteriaceae

Abstract

The root of Terminalia glaucescens, stem-bark of Mangifera indica and leaves of Mitracarpus villosus were screened for antibacterial activities against 23 carbapenem-resistant Enterobacteriaceae (CRE) isolates. The phyto-constituents of the plants were extracted by cold maceration. Disc-diffusion and broth microdilution methods were used to determine the antibacterial activity and the minimum inhibitory concentration, respectively. The sensitivity of the isolates to the methanol extracts of the plant parts was between four to eight isolates (10 – 26.5 mm) including Enterobacter aerogenes, Proteus mirabilis and Escherichia coli, with the highest activity shown by Mitracarpus villosus. An overall higher activity was however observed with the ethanol extracts of the plant parts with potency on twelve to fifteen isolates (9 – 18.5 mm) including Enterobacter aerogenes, Proteus mirabilis, Escherichia coli and Klebsiella pneumoniae. Generally for all methanol extracts, a constant MIC value 100 mg/ml was observed for the susceptible isolates except two Enterobacter aerogenes isolates with MIC of 1 mg/ml while the MIC value of the ethanol extracts ranged from ≤ 0.1 – 100 mg/ml. Ethanol extracts of stem-bark of Mangifera indica and leaves of Mitracarpus villosus exhibited considerably higher activities compared to other extracts with low MIC values. The phytochemical screening showed that the extracts contained at least five bioactive metabolites with alkaloids, tannin and flavonoids present in all. The plants used in this study show promising antibacterial activity that can be explored in the treatment of multi-drug resistant Enterobacteriaceae infections.