Browsing by Author "Esra, Rachel"

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    Mathematical modelling of the population impact of screening for Chlamydia Trachomatis and Neisseria gonorrhoeae in South Africa
    (2018) Esra, Rachel; Johnson, Leigh
    A large proportion of chlamydial and gonococcal infections are asymptomatic. In lower- and middle-income countries like South Africa, where syndromic management is practiced, it is likely that a large proportion of curable STIs go untreated, as screening for asymptomatic STIs is rarely conducted. Due to the lack of empirical data on the efficacy of STI screening programs, dynamic mathematical modelling has been used to assess the impact of screening, but most previous modelling studies have focused on high-income settings. Here we utilize dynamic mathematical modelling to evaluate the potential impact of opportunistic STI screening programs on the incidence and prevalence of Chlamydia trachomatis and Neisseria gonorrhea in South Africa. We extended an existing agent-based model of heterosexual HIV and STI transmission in South Africa to investigate the impact of targeted screening strategies directed at high risk groups including youth, female sex workers, pregnant women and patients in HIV care. All four screening strategies resulted in reductions in general and key population STI transmission. Opportunistic STI screening of youth and ART patients were shown to be most effective and represent viable interventions for reducing STI transmission in the South African population. Additionally, we compared the modelled impact of a standardized screening program to results obtained from other published mathematical models of chlamydia screening. Differences between models could be attributed to differences in the modelled heterogeneity in sexual behaviour as well as differences in assumptions about immunity following chlamydia recovery.
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    The association between the oral and vaginal microbiome of young South African women
    (2019) Esra, Rachel; Jaspan, Heather; Balle, Christina
    Bacterial vaginosis (BV) and periodontal disease (PD) are conditions characterised by reduction of healthy bacterial communities in the vaginal and oral microbiomes respectively. Both BV and PD are associated with an increased risk of preterm labour and negative birth outcomes, yet it is unknown whether PD and BV are independent risk factors or may be interrelated. Understanding the health risks associated with pregnancies in young women is critical for developing new preventative interventions and for informing guidelines. Current knowledge of what constitutes a healthy microbiome is largely based on North American studies and may not be applicable to the South African population. This study characterises the oral and vaginal microbiome of South African female adolescents and investigates the association between alterations in oral bacterial diversity and BV in young South African women. DNA was extracted from matched lateral vaginal wall, saliva and periodontal samples and V4 16S sequencing was performed using MiSeq technology. The composition of the core oral microbiome of South African female adolescents was found to be similar to descriptive studies published in other populations. We additionally report a description the vaginal microbiome that is in agreement with previous studies in the South African population. PD-associated bacterial species were enriched in the oral microbiome of women with clinically diagnosed BV and in those with Lactobacillus iners dominant vaginal community types (VCTs) compared to asymptomatic women and those with L. crispatus dominated VCTs respectively. While this data provides evidence in support of a relationship between oral and vaginal dysbiosis, it unclear in which compartment bacterial dysbiosis would originate, should the association holds true.