Browsing by Author "Barth, Dylan Dominic"

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    Open Access
    AFROStrep (SA): a surveillance system for group A streptococcal infection in South Africa
    (2018) Barth, Dylan Dominic; Engel, Mark E; Mayosi, Bongani M
    BACKGROUND AND AIMS OF THE THESIS: Group A β-haemolytic Streptococcus (GAS) also known as Streptococcus pyogenes, is responsible for a wide range of invasive and non-invasive GAS diseases. Prevalence and incidence data on GAS from developing countries are largely lacking when compared with industrialised nations. This thesis sought to (1) establish the South African arm of the AFROStrep biorepository and clinical database for patients with invasive and non-invasive GAS infection, (2) identify and summarize all published studies of laboratory-confirmed GAS infection in Africa, (3) describe, from national laboratory data, the incidence of invasive and non-invasive GAS in South Africa and, (4) conduct a prospective, surveillance study in order to determine the molecular epidemiology of GAS in Cape Town, South Africa over a 12-month period. METHODS: A systematic review was conducted on population-based studies reporting on the prevalence of laboratory-confirmed GAS infection among patients living in Africa (Study 1). A retrospective study of the incidence of GAS infection was conducted on data obtained from the National Health Laboratory Service between 2003 – 2015 (Study 2). The AFROStrep registry and biorepository (based in Cape Town) was established and through passive surveillance, laboratory confirmed invasive and non-invasive GAS cases were collected over a 12-month period. The molecular analysis of invasive and non-invasive infection was determined using emm type sequencing to provide insight into vaccine development (Study 3). RESULTS AND DISCUSSION: The pooled prevalence of GAS pharyngitis in Africa was determined to be 21% (95% CI, 17% to 26%). The incidence rates of laboratory-confirmed non-invasive GAS infection in the South African public sector appears to have declined over the last 13 years. Given the possibility that the lower incidence of invasive and non-invasive GAS infection found in our study is due to infrequent submission of specimens for microbiological culture by health practitioners, our findings may be an underestimate of the true burden of disease in South Africa. In our prospective surveillance study, 46 different emm types were identified. The most prevalent emm types were M76 (16% of isolates), M81 (10%), M80 (6%), M43 (6%), and M183 (6%) and were almost evenly distributed between invasive and non-invasive GAS isolates. When compared against the putative 30-valent vaccine under development, four of our most prevalent emm types are not included; vaccine coverage (i.e. vaccine type and non-vaccine type-killing) for non-invasive and invasive GAS infection in our setting was 60% and 59% respectively, notably lower than coverage in developed countries. CONCLUSION: This work provides evidence for a significantly high prevalence of GAS pharyngitis in Africa. While GAS surveillance in South Africa indicates a declining incidence of GAS disease in parts of the country over the last thirteen years, the findings may be an underestimate of the true burden of disease, demonstrating the need for accurate and comprehensive surveillance of GAS in South Africa. Finally, this research showed a low potential vaccine coverage in our setting and thus, emphasises the need for a reworking of the potential vaccine formulation to improve coverage in areas where the burden of disease is high.
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    The effect of distance to health facility on the maintenance of INR therapeutic ranges in rheumatic heart disease patients from Cape Town
    (2013) Barth, Dylan Dominic; Engel, Mark E; Mayosi, Bongani
    Part A: is the research protocol which outlines the background and the process of this research. This study is a population-based observational study nested within the Groote Schuur Hospital (GSH) cohort of a global study, REMEDY which is a prospective, multicentre, hopital-based registry for rheumatic heart disease (RHD). This study made use of geographical information systems (GIS) as a tool to investigate the effect of distance on the maintenance of INR therapeutic ranges in RHD patients. Part B: elaborates on the background and highlights the importance of this research by exploring the existing theoretical and empirical literature relevant to the topic. It describes the importance of the maintenance of the INR therapeutic range and how geographical factors can influence patient adherence to medication, and how it can act as a barrier to access health care. It provides examples of how GIS has been used to investigate the effect of distance on adherence in other studies. This literature review aimed to establish whether the maintenance of therapeutic ranges in RHD patients on anticoagulant therapy is correlated with the distance travelled from patient's residence to the clinic where INR monitoring takes place. Part C: presents the entire project in a format suitable for journal submission. The background of this research project is summarised and the results are presented and discussed.
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    Effect of distance to health facility on the maintenance of INR therapeutic ranges in rheumatic heart disease patients from Cape Town: No evidence for an association
    (BioMed Central, 2015-06-01) Barth, Dylan Dominic; Zühlke, Liesl; Joachim, Alexia; Hoegger, Tyler; Mayosi, Bongani M; Engel, Mark E
    Background: Lack of adherence to international normalised ratio (INR) monitoring in rheumatic heart disease (RHD) patients is a contributor to cardio-embolic complications. This population-based observational study investigated whether the distance between home and an INR clinic affects the maintenance of therapeutic INR in RHD patients on warfarin. Methods: Residential addresses, INR clinics, and INR results of patients with RHD were extracted from the Cape Town component of the Global Rheumatic Heart Disease Registry (REMEDY) database. Addresses of homes and INR clinics were converted to geographical coordinates and verified in ArcGIS 10®. ArcGIS 10® and Google Maps® were used for spatial mapping and obtaining shortest road distances respectively. The travel distance between the home and INR clinic was correlated with time within therapeutic range (TTR) using the Rosendaal linear interpolation method, and with the fraction of INR within range, based on an average of three INR readings of patients and compared with recommended therapeutic ranges. Results: RHD patients (n=133) resided between 0.2 km and 50.8 km (median distance, 3.60 km) from one of 33 INR clinics. There was no significant difference in the achievement of the therapeutic INR between patients who travelled a shorter distance compared to those who travelled a longer distance (in range = 3.50 km versus out of range = 3.75 km, p=0.78). This finding was the same for patients with mechanical valve replacement (n=105) (3.50 km versus 3.90 km, p=0.81), and native valves (3.45 km versus 2.75 km, p=0.84). Conclusions: There is no association between the maintenance of INR within therapeutic range amongst RHD patients in Cape Town and distance from patients’ residence to the INR clinic.