Antibacterial activity of plant parts selectively consumed by chimpanzees

Abstract

This study was conducted to determine the antibacterial properties of plant parts selectively eaten by chimpanzees in Kalinzu forest. Plant part samples obtained were freeze dried and dry samples were used for extraction using standard solvents. Dichloromethane, water, acetone and Methanol were first compared because of the differences in polarity of different plant compounds. Extraction was performed on rotator Labotec model 20.2 shaking apparatus with a 5 ml: 0.75 g solvent to sample weight ratio. The antibacterial activity of the plant extracts was quantified using the micro plate dilution method to determine the Minimum Inhibitory Concentration (MIC) values of each plant extract against each test bacteria species. Reference strains of Escherichia coli (gram negative) ATCC25922 and Staphylococcus aureus (Gram positive) ATCC 25923 were used. Other Bacterial strains used for antimicrobial assays were obtained from Chimpanzees faecal material. Selective media were chosen to culture an adequate variety of bacterial types. Antibiotic sensitivity patterns of the selected Gram-positive and Gram-negative bacterial strains used in the study were evaluated. Methanol solvents produced the extract that resulted into the lowest MIC against the test bacteria S. aureus. Plant parts from 8 out of the 10 species showed inhibition of bacterial growth at various extract concentrations. The least eaten plant parts showed more antibacterial activity than those consumed frequently and in large amounts. Bersama abysinica leaf and Aframomum angustifolium fruit inhibited the growth of five out of the six tested bacteria strains with the former exhibiting the lowest Minimum Inhibitory Concentration of 0.05 towards coagulative negative S. aureus. Diospyros abysinica and Prunus africana fruit were active against four out of the six bacterial strains tested. Among these bacterial strains, S. aureus was more vulnerable to inhibition while Klebsiella pneumoniae was most resistant. The growth of K. pneumonae was only inhibited by D. abysinica extract at the highest extract concentration of 25 mg/ml and was also found to be bactericidal. The extracts from the rest of the plant parts were bacteriostatic. B. abysinica and A. angustifolium extracts had strong antibacterial components and may be important in fighting Pseudomonas aeruginosa that was resistant to most standard antibiotics. Six out of the eight plant extracts that showed antibacterial activity were able to control the growth of S. aureus an indication of new avenues of controlling the S. aureus, resistant to antimicrobials especially menthicilin.