Abstract
With the steady increase in global antimicrobial resistance rates, concomitant witha recent paucity of novel antibiotic discovery, it is essential that new antimicrobial
compounds be discovered to prevent a return to the pre-antibiotic era over coming decades. Knowledge of the medicinal properties of traditional plants has given rise to many of the modern day medicines. Consequently, the aim of this work was to assess the antimicrobial and antibiofilm activities of a number of traditional African herbal remedies against a range of clinically important bacterial species.
After a pilot study was performed, Prosopis africana and Uvaria chamae were
selected from a range of medicinal plants due to their greater antimicrobial activity against
Pseudomonas aeruginosa, Staphylococcus aureus and Escherichia coli than the other
remedies tested. Crude extracts from P. africana (PAM, PAS and PAU) and U. chamae
(UCM, UCS and UCU) were prepared using maceration, Soxhlet and ultrasound
extraction method respectively. Cultures of both aerobic and anaerobic bacterial species were exposed to the crude extracts in agar-well diffusion and broth micro-dilution assays. In addition, semi-quantitative and quantitative antibiofilm assays were performed using PAS, PAU, UCS and UCU extracts against preformed biofilms of P. aeruginosa, S. aureus, S. epidermidis, Propionibacterium acnes and Clostridium difficile strains. Fractionation of the crude extracts was then performed using column chromatography; with antimicrobial, simple phytochemical and spectrophotometric analyses being performed on the resultant fractions.
It was found that all extracts had both bacteriostatic and bactericidal activity
against all of the bacterial species tested, although the Soxhlet and ultrasound extracts demonstrated a significantly greater activity than the maceration extracts. The extracts demonstrated antibiofilm activity against preformed biofilm of P. aeruginosa, S. aureus, S. epidermidis, P. acnes and C. difficile strains by reducing the density of biofilm biomass significantly by at least 11.5 % compared to the control. In the antimicrobial activity test, the fractions that were the most effective against P. aeruginosa and S. aureus with MIC and MBC value ranges of 0.195 % - 2.60 % and 0.391 % - 6.25 % respectively, contained the following phytochemical groups; saponins, quinones, flavonoids, and alkaloids which have been previously shown to be antimicrobial by other workers. Absorption spectrum analysis further suggests that the fractions of U. chamae and P. africana with the greatest
antimicrobial activity might contain flavonoid-related compounds as their major active components.
This study demonstrated that P. africana and U. chamae extracts are effective
antimicrobial and antibiofilm agents and therefore the isolation and evaluation of their active ingredients could yield potentially new leads to fight antimicrobial resisance.
| Date of Award | Jul 2019 |
|---|---|
| Original language | English |
| Awarding Institution |
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| Supervisor | Tim Aldsworth (Supervisor), Jamie Beddow (Supervisor), Jess Rollason (Supervisor), Lauren Acton (Supervisor) & Larysa Paniwnyk (Supervisor) |