Antibiotic-resistant Staphylococci in South Africa-A One Health Approach
Date
2024-12
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Stellenbosch : Stellenbosch University
Abstract
Staphylococci cause a wide range of infections in humans and animals, with Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus hominis and Staphylococcus haemolyticus the most common Staphylococcus species implicated in healthcare and community acquired infections. The emergence and dissemination of antibiotic resistance (ABR) among Staphylococcus species has complicated empiric treatment practices and limited treatment options, leading to increased mortality. The World Health Organization (WHO, 2015) declared antimicrobial resistance a threat to the treatment of infections. The “One Health” initiative addresses health care challenges holistically by including human health, animal health and environmental health to achieve better public health outcomes. This approach is being adopted by the WHO to mitigate the problem of ABR and research across these sectors is required. This study investigated ABR rates and described the molecular resistance mechanisms and population structures of staphylococci from community, clinical and farm settings. This was achieved by employing both traditional culture and phenotypic antibiotic susceptibility testing as well as whole genome sequencing. A systematic review was conducted to understand trends, strengths, and limitations in the area of ABR in staphylococci other than Staphylococcus aureus (SOSA) in animals. The findings suggested that there is high tetracycline and penicillin resistance among SOSA organisms in livestock and companion animals in Africa. The review also highlighted the lack of strain typing of SOSA in Africa and that research was more focused on cattle. To employ a One Health approach, this study therefore included pigs, which are common livestock in the Western Cape province of South Africa, stool samples from healthy children in the community, and clinical isolates. S. haemolyticus and S. epidermidis were identified in all three settings, and S. borealis was identified from the pigs and the healthy community-based children, the first report of this species in Africa. High rates of tetracycline resistance were observed amongst pigs and human contacts on the pig farms. The majority of the healthy community-based children were colonised by methicillin resistant SOSA, and in the clinical isolates high rates of multidrug resistance were observed. The distribution of tetracycline resistance suggests that pig farms might be a “hotspot” for tetracycline resistance which is then transferred via the community with moderate resistance rates, to clinical settings with lower rates of tetracycline resistance. The tetracycline resistance gene tetK was seen across all selected settings in SOSA, as was the erythromycin resistance gene, ermC. No common strain types were circulating across all selected settings. However, certain S. haemolyticus strain types were identified in community and clinical settings. Our ability to conclude on genetic relatedness in the selected settings was limited by inconsistent species distribution and sample size. The findings suggest that S. haemolyticus is predominant in the community and might be spreading into the clinical and farm settings while Mammaliicoccus sciuri is predominant in the farm setting with potential dissemination into the community. Although the number of Staphylococcus aureus from the study was small, SOSA were more resistant than S. aureus with diverse antibiotic resistance genes; evidence of SOSA as a reservoir of ABR genes.
Description
Thesis (PhD)--Stellenbosch University, 2024.