Small interfering RNAs targeting agrA and sarA attenuate pathogenesis of Staphylococcus aureus in Caenorhabditis elegans

The use of small interfering RNA (siRNA) gene silencing is a promising therapeutic option as it does not impose selective pressure on bacteria that is often associated with the development of resistance. The study assessed the effect of siRNA targeted to sarA and agrA in S. aureus and the relationship between the transcriptional response, biofilm formation and pathogenicity. Methodology: siRNAs designed against agrA and sarA were electroporated into methicillin-resistant and methicillin-susceptible S. aureus strains. mRNA levels, growth kinetics, biofilm formation and minimal inhibitory concentration were measured. Efficacy of siRNA in bacteria was assessed using survival assays in a C. elegans model. Differences in gene expression before and after siRNA treatment were anaysed using the paired t-test, while the log rank test was used to assess the significance of any difference among survival rates of nematodes. Results: Biofilm formation decreased significantly in siRNA treated strains and growth rates of siRNA treated strains were significantly higher compared to untreated strains. We observed significant decreases in the transcriptional response in siRNA treated strains, with concomitant significant increases in the lifespan of C. elegans worms exposed to siRNA-treated versus untreated strains. Conclusions: siRNA targeted to agrA and sarA lowered mRNA transcription and pathogenicity of S. aureus.