Masters Degrees (Microbiology)

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Browsing Masters Degrees (Microbiology) by Subject "Air -- Microbiology -- Environmental aspects"

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    Microbial indoor air quality and the use of UVGI treatment in the Western Cape province, South Africa
    (Stellenbosch : Stellenbosch University, 2022-12) De Beer, Tanya; Jacobs, Karin; Stellenbosch University. Faculty of Science. Dept. of Microbiology.
    ENGLISH ABSTRACT: Humans have dramatically increased the amount of time spent indoors in recent years. This has increased our exposure to all elements within indoor air, including building materials, various gases, climatic conditions, as well as microorganisms. Bacteria and fungi are the main constituents of microbial indoor air, most of which are harmless to humans. However, certain microorganisms have adapted to airborne dispersal and can cause adverse health conditions including respiratory illnesses as well as allergies, posing a threat to the basic human right to clean indoor air. The group of microorganisms related to the Mediterranean climate of the Western Cape province is relatively understudied and requires further investigation in order to set recommended limits for indoor pollutants. Furthermore, air sterilisation technologies, such as UV and ozone irradiation systems, have been refined to remove harmful pathogens from indoor environments. With the widespread use of public transportation, the amount of people being exposed to harmful bacteria and fungi have increased due to the easy transmission of these microorganisms in close proximity. As a result, bacteria and fungi constitute a significant biological component of indoor air environments and therefore require a better understanding. Using culture-dependent air sampling methods and sequencing, the diversity of the vegetative bacteria and fungi in residences of the Western Cape province was investigated. Moreover, the susceptibility of these microorganisms to UV and ozone exposure was tested to determine the effectiveness of these indoor air treatment methods. It was found that airborne microbial concentrations showed a significant positive correlation with the temperature, relative humidity, and CO₂ concentrations of the residences analysed in this study. Additionally, all but three residences had microbial concentrations within the recommended guidelines of ~1000 CFU/m³ set by the World Health Organisation. The predominant bacterial genera detected in the residences were Bacillus, Staphylococcus, and Micrococcus and the predominant fungi were species of Cladosporium, Penicillium, Alternaria, Epicoccum, Aspergillus, and yeasts. It was established that the dry Mediterranean climate of this province generates a unique indoor microbial diversity that is consistent with other studies examining indoor air in similar climates. Many of the microbial species detected in the residences are known to cause adverse health effects in humans, emphasising the need to remove indoor contaminants. Lastly, it was revealed that bacteria and fungi were more susceptible to ozone disinfection than UV germicidal irradiation (UVGI). The use of UVGI in public transport vehicles showed that the number of airborne microorganisms is significantly affected by the number of passengers in the vehicle, regardless of an active UVGI system. Although ozonation was shown to be a more powerful sterilisation method, it is still advised to use UVGI as no harmful by-products are formed. Future studies should include more sampling locations as well as the development of next- generation sequencing methodology for microbial air samples to include difficult to culture microorganisms.