Dissertation submitted to the Faculty of Health Sciences, University of the
Witwatersrand, Johannesburg, in fulfillment of the requirements for the
degree of Master of Science in Medicine.
Johannesburg, 2012 / Oral candidiasis is an infection prevalent in immunocompromised individuals. The main
causative agent is Candida albicans. Many antifungal agents are available and are effectively
used. However, due to the development of drug resistance, toxicity and poor solubility resulting
in poor absorption; medicinal plants have been investigated. Dodonaea viscosa var. angustifolia,
an indigenous South African plant has shown to have an antifungal effect including inhibition of
adherence of C. albicans to oral epithelial cells; which is the crucial first step of infection. This
study investigated the effect of the crude extract on the ultrastructure of C. albicans cell wall,
which might be responsible for the reduced adherence to oral epithelial cells. The effect of the
plant extract on C. albicans germ tube and biofilm formation was also studied since biofilm
structure allows for high resistance to antifungal agents and host defense mechanisms.
Crude plant extracts were prepared using dried leaves and acetone. Three C. albicans strains
were used throughout the study. Minimal fungicidal concentrations of plant extract were
determined using a microdilution technique. Three subinhibitory concentrations 3.125, 1.562 and
0.781 mg/ml were selected for further studies. The effect of these subinhibitory concentrations of
plant extract on the C. albicans cell wall structure, cell membrane, germ tube formation, biofilm
formation and cell wall proteins were studied using transmission electron microscopy, light
microscopy, scanning electron microscopy and SDS-PAGE respectively.
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The subinhibitory concentrations of crude plant extract rendered C. albicans cell wall thinner and
at some places caused cell wall breakage and disruption. This effect increased with a decrease in
plant extract concentration. The cell membrane was also damaged by the plant extract showing
increased undulation. This effect was not concentration dependent. The subinhibitory
concentrations decreased C. albicans germ tube formation and the effect increased with an
increase in concentration. Biofilm formation was reduced by the plant extract and in addition,
hyphal formation by cells within the biofilm was also reduced. However, SDS-PAGE showed
that on a molecular level, the plant extract did not remove any specific adhesin proteins from the
cell wall.
The crude plant extract of D. viscosa var. angustifolia at high concentrations, kills C. albicans
and at low concentrations, renders the surviving cells avirulent. Therefore it has the potential to
be developed into an effective therapeutic agent to treat and prevent oral candidiasis. However,
further research is required to identify the mode of action of the extract, the specific chemicals
responsible for the effect, and the cytotoxicity.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/13625 |
| Date | January 2012 |
| Creators | Naicker, Serisha Devi |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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