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Doctoral Degrees (Microbiology and Infection Control)

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Browsing Doctoral Degrees (Microbiology and Infection Control) by Subject "Theses--Medical microbiology."

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    Aspects of the epidemiology of malaria in Natal Province, Republic of South Africa.
    (1990) Sharp, Brian Leslie.; Van den Ende, Jan.
    This study investigated aspects of the epidemiology of malaria in the Natal province of the Republic of South Africa. In this study the Collins English dictionary definition of epidemiology is used where it is defined as the branch of medical science concerned with the occurrence, transmission and control of an epidemic disease. Malaria has been a notifiable disease in the Republic of South Africa since 1958. Retrospective malaria case data from the Natal province as a whole was analyzed and the data from the KwaZulu and Natal areas of the province compared. Malaria cases were reported from 35 of the 65 magisterial districts in Natal province during the study period. In the Natal areas 91.5% of the cases were reported from eight districts and in the KwaZulu areas 96.4% of the cases came from three districts or as imports from Mozambique. The overall attack rate for both the Natal and KwaZulu areas using the total population figures for each area were very similar for the period 1986-1988 at 0.71 and 0.70 per 1000 head of population for the respective areas. The disease showed a distinct seasonal pattern in the KwaZulu areas with 86.9% of the cases being classified as indigenous and only 13.1% as imported. In the Natal areas, however, the seasonal pattern was not as marked and only 12.1% of the cases were recorded as indigenous and in excess of 82% as imported. Three species of the Anopheles gambiae complex were found to occur sympatrically in Natal province, namely: An. arabiensis, An. quadriannulatus and An. merus. Of these species An. arabiensis was found to occur at five localities during or after the notification of indigenous malaria cases from these areas. Due to the sympatric distribution of these species particular emphasis was placed on species identification and in particular the biting behaviour and control of An. arabiensis was investigated. The study found both morphological and behavioural differences between populations of An. arabiensis from those areas of the province with an intra-domiciliary residual insecticide vector control programme and those from the unsprayed areas. In the unsprayed areas the majority of the indoor resting An. arabiensis had fed on man whereas in the sprayed areas the majority of the indoor resting An. arabiensis were bovine fed. In the sprayed areas, however, the majority of the An. arabiensis caught leaving huts had fed on man. The percentage survival of bloodfed An. arabiensis caught leaving huts in the DDT sprayed area was in excess of 72%. The data strongly suggest that optimal control of An. arabiensis will not be achieved using the current control strategy of the annual application of intra-domiciliary DDT.
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    The interaction of lymphogranuloma venereum and oculogenital chlamydia trachomatis with human keratinocytes and cervical epithelium.
    (2010) Joubert, Bronwyn C.; Sturm, Adriaan Willem.
    Background. Keratinocytes are the first target of infection for lymphogranuloma venereum (LGV) Chlamydia trachomatis, yet they have been omitted from pathogenesis studies. We infect keratinocytes and cervical cells with C. trachomatis and hypothesize different growth and cytotoxicity profiles among the strains. Methods. HaCaT human keratinocytes and ME-180 cervical cells were infected with C. trachomatis (multiplicity of infection (MOI) 0.025) serovars L1, L2, L3, 3 LGV clinical isolates or serovar E and incubated at 37 or 33°C for 5 days. Cytotoxicity was quantified daily using the CytoTox96® Non-Radioactive Cytotoxicity Assay, cells stained with the MicroTrak C. trachomatis Culture Confirmation kit and growth quantified by area of 100X photographs covered by Chlamydia. HaCaT and ME-180 cervical cells were infected with C. trachomatis (MOI 0.25) serovar L2 or E, incubated at 37 or 33°C for 48 hours and viewed with a transmission electron microscope (TEM). Mitochondrial activity was quantified using the MTT assay. The DeadEndTM Colorimetric TUNEL System with C. trachomatis Culture Confirmation kit as a counter-stain was used to assess cell death in infected versus uninfected cells. The BioVisionTM CaspGLOW Fluorescein Caspase Staining Kit and Transwell® Permeable Supports was used to differentiate between apoptosis mediated by cell-to-cell contact or a secreted molecule. Results. Growth in ME-180 versus HaCaT cells at 37°C was similar, but slower at 33 versus 37°C in HaCaT cells (p < 0.05). By day 5 L2 had grown faster than other strains in HaCaT cells at 37°C (p < 0.05), faster than clinical isolates in ME180 cells (p < 0.01), and faster than serovar E, and 2 clinical isolates at 33°C (p < 0.01). After 5 days L2 induced cytotoxicty was 11% in ME180 cells, which was higher than the clinical isolates (p < 0.01). In HaCaT cells at 33°C L2 EB were identified in a non-membrane state in the cytoplasm but not in the inclusion at 48 hours post infection. Serovar E but not L2 caused mitochondrial swelling at 1 h post infection in HaCaT cells at 37°C. This corresponded with a 16% reduction in mitochondrial activity (p < 0.001). TUNEL assay analyses demonstrated numerous dead cells adjacent to chlamydial inclusions for strains L2 and L3 but not L1 and E. An elevated number of caspase positive cells was detected in uninfected cell monolayers exposed to both L2 and E at 37°C but not 33°C. Conclusions. 1. C. trachomatis infects human keratinocytes in vitro. 2. Fresh clinical isolates behaved differently to the L2 reference strain. This demonstrates the need for fresh clinical isolates in pathogenesis studies of LGV. 3. In HaCaT cells at 33°C serovar L2 EB leave the intact inclusion and migrate through the cytoplasm in a non-membrane bound state 4. C. trachomatis induces apoptosis in uninfected cells exposed to infected cells via a secreted molecule at 37°C. This is more marked with serovar L2 exposure than serovar E exposure.