In vivo anti-staphylococcal activity of roselle (Hibiscus sabdariffa L.) calyx extract in Drosophila model of infection

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Introduction: The emergence of antibiotic-resistant Staphylococcus aureus is a major threat for worldwide communities. To overcome such serious problem, the discovery of novel antibacterial agents through exploration of diverse potential sources is essential. The aim of this research was to investigate the in vivo anti-staphylococcal activity of roselle (Hibiscus sabdariffa L.) calyx extract against S. aureus in fruit flies (Drosophila melanogaster) model of infection.Methods: Roselle calyces were dried and extracted with ethanol using maceration method. Wildtype fruit flies were infected with S. aureus and subjected to survival assay, bacterial load examination, and gene expression analysis, in the presence or absence of roselle calyx extract. Survival and bacterial load analysis were subsequently performed on immunodeficient fruit flies using similar protocols.Results: Reduction of host survivorship accompanied by increasing level of bacterial proliferation was observed in group of wildtype fruit flies infected with S. aureus. These phenotypic events were further augmented in mutant flies devoid of component for antibacterial immune responses. Nevertheless, reduction of bacterial load and improvement of host survival were demonstrated in either wildtype or immunodeficient fruit flies upon treatment with roselle calyx extract after bacterial challenge, irrespective of immune status.Conclusion: Collectively, our results demonstrated the in vivo antibacterial activity of roselle calyx extract against S. aureus in Drosophila model of infection and this was not due to induction of immune response in the host.