Browsing by Author "Cursons, Raymond Thomas Michael"

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    Classification and identification of the aetiological agents of primary amebic meningo-encephalitis, together with preliminary investigations of public health measures : a thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Microbiology at Massey University
    (Massey University, 1974) Cursons, Raymond Thomas Michael
    The taxonomy of the aetiological agents of Primary Amebic Meningo-encephalitis (PAM) was investigated to determine the reliability of the common features of the three current schemes. It is concluded that the scheme of Singh & Das (1970) is the most suitable and should be generally adopted. The acceptance of one scheme will remove much of the confusion which characterizes the classification of these organisms. Current identification methods that differentiate between Naegleria gruberi (the non-pathogen) and Naegleria fowleri (the pathogen) were also investigated over a wider range of parameters than previously, to establish their relative usefulness. The conclusions of this investigation are presented in Tables XXII and XXIII. The controversial identification of the 1968 New Zealand cases (isolates BK & BL) as a Myxomycete by Mandal et al. (1970) was re-examined. Evidence is presented to demonstrate that they are N. gruberi. It was established that there was no general selection for the non-pathogen over the pathogen at 37°C as indicated by their respective QO2 values at 27°C and 37°C. That there is potential for adaptation to a range of temperatures was shown. The failure of chlorine as a disinfectant for these soil-amebae was also examined. The ineffectiveness of normal levels of chlorination was confirmed and therefore the use of NaCl and the basic dyes Malachite Green and Brilliant Green investigated. It was found that no amebae could survive a concentration of (1.5%)(W/V) of NaCl in axenic culture, of 1.5 µg/cm 3 of Malachite Green and of 3.0 µg of Brilliant Green.
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    Pathogenic free-living amebae-occurrence in New Zealand thermal regions, together with investigations into their disinfection, immunity and virulence : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Microbiology at Massey University, New Zealand
    (Massey University, 1978) Cursons, Raymond Thomas Michael
    Pathogenic free-living amebae (PFLA), of which Naegleria fowleri was the predominant pathogenic species, were isolated from 6 out of 10 pools sampled from the Hamilton, Rotorua and Gisborne Health Districts. The majority of these PFLA contaminated-pools occurred in the Matamata-Taupo region, and this localized geographical distribution appeared to be influenced, in part, by the particular physical and chemical properties of the pool. 'High-risk' pools, which exhibited a high incidence of isolations of PFLA, were shown to be natural pools, i.e. soil enclosures, as opposed to concrete constructed pools. PFLA were also isolated from the soil, and it was thought that soil acted as a reservoir of PFLA. No seasonal distribution in the occurrence of PFLA in thermal pools was noticed. A comparative study on the disinfecting potential of chlorine, chlorine dioxide, ozone and deciquam 222 for PFLA showed that all 4 disinfectants possessed amebicidal properties, but only at higher levels than those normally used for disinfecting bacteria. Of the 4 disinfectants, deciquam 222 proved to be the most effective amebicide, followed by chlorine, chlorine dioxide and ozone. An immunological survey of normal human sera for the presence of antibodies to either pathogenic or non-pathogenic Naegleria and Acanthamoeba spp. established that human sera had a titre ranging between 1/5 - 1/20 for Naegleria spp. and between 1/5 - 1/80 for Acanthamoebae. No discrimination in titres was observed between blood groups or sexes and fluorescein-labelled class-specific immunoglobulins showed that these antibodies belonged mainly to both the Ig M and Ig G classes. It was also shown that fresh adult human sera, as opposed to cord or specific hyperimmune-rabbit sera, contained a heat-labile neutralizing factor which inhibited the formation of cytopathic effects (CPE) in Vero cell culture by Acanthamoeba culbertsoni, but not by N. fowleri. Homologous, as well as heterologous antigens of Naegleria spp. were however, shown to cross-react with both the in vitro, macrophage inhibition factor assay, and in vivo, delayed hypersensitivity, correlates of cell-mediated immunity. Finally, this study also demonstrated that both pathogenic and non-pathogenic species of Naegleria and Acanthamoeba secreted both an extracellular phospholipase 2 and lysophospholipase into their axenic cultures. The relative production of phospholipase 2 correlated with the formation of CPE in Vero cell culture by either amebae, or by cell-free filtrates from axenic cultures of amebae. The relative level of production of this enzyme appeared to influence the virulence and hence pathogenic-potential of these micro-organisms.