Abstract
The emergence of antibiotic-resistant Pseudomonas aeruginosa is one of main health issues in global communities. To overcome such threat, the discovery of novel antibacterial agents is indispensable. This study aimed to evaluate the in vivo antipseudomonal activity of Ulva reticulata extract in Drosophila model of infection. Ethanolic extract of Ulva reticulata was prepared using maceration method and the extract was subsequently assessed for its in vivo antibacterial effect against P. aeruginosa using survival assay, bacterial load enumeration, and gene expression analysis in the wildtype Drosophila. Survival and bacterial load analysis were further performed in a similar fashion on the mutant flies devoid of component responsible in the activation of immune responses against P. aeruginosa. Decline in the survival of infected host accompanied by augmentation of bacterial proliferation was documented in the wildtype Drosophila upon infection with P. aeruginosa. These phenotypic events were further amplified in immune-deficient mutant Drosophila. Nevertheless, improvement of host survivorship and reduction of bacterial burden were demonstrated in both wildtype or immune-deficient mutant flies upon treatment with Ulva reticulata extract after bacterial challenge. Our data demonstrated in vivo antipseudomonal activity of Ulva reticulata extract and thus provide a valuable information about its future potential for health promotion.
Highlights
The emergence of pathogenic bacteria that are resistant to antibiotics presents a serious problem to the stability of public health (Levy and Marshall 2004; Gelband et al 2015)
The survivorship of infected flies became greatly enhanced once maintained in the presence of Ulva reticulata extract at a concentration as much as 2.5% w/w or tetracycline. From this experiment we demonstrated that the presence of certain concentration of Ulva reticulata extract in the food was sufficient to rescue P. aeruginosa-infected D. melanogaster from early death phenotype, indicating the in vivo antibacterial effect of Ulva reticulata extract against P. aeruginosa was achieved in a dose-dependent manner
As a result of this assay, we found that treatment of P. aeruginosa-infected flies with either tetracycline or Ulva reticulata extract was greatly useful to reduce the bacterial load (Figure 2b), suggesting that bacterial growth inhibition by tetracycline or Ulva reticulata extract could lead to the increased survivorship of infected flies
Summary
The emergence of pathogenic bacteria that are resistant to antibiotics presents a serious problem to the stability of public health (Levy and Marshall 2004; Gelband et al 2015). Recent reports described that ethanolic extract of Ulva reticulata demonstrated excellent in vitro activities against several human pathogenic bacteria, including P. aeruginosa (AlSaif et al 2014; Ravikumar et al 2016). Despite such potential, little information is available regarding the in vivo antibacterial activity of this particular marine species against P. aeruginosa
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