Several yeast species had previously been isolated from water systems in the North West
Province, South Africa. Some of the identified species had, in other studies, been associated
with superficial mucosal infections to life threatening diseases. Antifungal drugs are used to
treat such yeast infections. However, due to prophylactic usage and continuous exposure
some yeast species have developed resistance to some antifungal agents. The aim of this
study was to determine the diversity and antifungal susceptibility of yeasts in selected rivers,
Mooi River and Harts River in the North West Province, South Africa. Waters samples were
collected from the rivers in summer and winter seasons. Physico-chemical parameters such
as pH, temperature, total dissolved solids, chemical oxygen demand, nitrates and
phosphates were measured to determine the water quality. Yeast colonies were enumerated
at room temperature and 37°C using yeast-malt-extract agar (containing 100 ppm
chloramphenicol). Pure isolates from 37°C were identified by biochemical tests and 26S
rRNA gene sequencing. Yeast sequences of isolated yeasts were sent to Genbank.
Phylogenetic tree was conducted to determine phylogenetic relationship between the yeast
isolates. Disk diffusion antifungal susceptibility tests were conducted on the yeast species.
Physico-chemical parameters of the water were within target water quality range for livestock
farming but in most sampling sites out of range for irrigation use. pH, Nitrates, phosphates
and chemical oxygen demand levels ranged from 7.40 to 8.64, 0 to 5.4 mg/L, 0 to 7.14 mg/L
and 31 to 43 mg/L, respectively. Elevated levels of total dissolved solids were measured in
all the sampling sites. Total yeast counts ranged between 320-4200 cfu/L and 27-2573 cfu/L
for room temperature and 37˚C. All the yeast colonies isolated were non-pigmented.
Diazonium Blue B tests determined the yeasts isolates as ascomycetes. Haemolysin and
extracellular enzyme production tests were negative on all the isolates. Yeasts isolates were
identified and belonged to the genera Arxiozyma, Candida, Clavispora, Cyberlindnera,
Lecythophora, Pichia, Saccharomyces, and Wickerhamomyces. Saccharomyces cerevisiae
and Candida glabrata were mostly isolated species. Furthermore, the results indicated that
levels of yeast could be correlated to physico-chemical quality of water. A large number of
isolates were resistant to azoles, especially fluconazole as well as other antifungal classes.
Most of the Candida species were resistant to almost all the antifungals. Several of the
isolated yeast species are opportunistic pathogens. They could cause infections in sensitive
individuals during occasional direct contact especially immune compromised people.
Resistance of these yeast species to antifungal agents is a major health concern. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015
| Identifer | oai:union.ndltd.org:NWUBOLOKA1/oai:dspace.nwu.ac.za:10394/15431 |
| Date | January 2014 |
| Creators | Monapathi, Mzimkhulu Ephraim |
| Source Sets | North-West University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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