Journal Article

Effects of short interfering RNA against methicillin-resistant <i>Staphylococcus aureus</i> coagulase <i>in vitro</i> and <i>in vivo</i>

Katsunori Yanagihara, Miwa Tashiro, Yuichi Fukuda, Hideaki Ohno, Yasuhito Higashiyama, Yoshitsugu Miyazaki, Yoichi Hirakata, Kazunori Tomono, Yohei Mizuta, Kazuhiro Tsukamoto and Shigeru Kohno

in Journal of Antimicrobial Chemotherapy

Published on behalf of British Society for Antimicrobial Chemotherapy

Volume 57, issue 1, pages 122-126
Published in print January 2006 | ISSN: 0305-7453
Published online December 2005 | e-ISSN: 1460-2091 | DOI: http://dx.doi.org/10.1093/jac/dki416
Effects of short interfering RNA against methicillin-resistant Staphylococcus aureus coagulase in vitro and in vivo

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Objectives: The emergence of antibiotic-resistant bacteria such as Staphylococcus aureus calls for inventive research and development strategies. Inhibition of bacterial pathogenesis may be a promising therapeutic approach in this regard. The gene-silencing effect of short interfering RNA (siRNA) is useful for this strategy. We investigated the efficacy of siRNA on the expression of coagulase because it is the one of the most important enzymes in the pathogenesis of methicillin-resistant S. aureus (MRSA) infection.

Methods: We designed and synthesized 21 bp siRNA duplexes against staphylococcal coagulase. RT–PCR was performed to determine whether the siRNAs inhibit the expression of the coagulase mRNA and radio-labelled siRNA was used to confirm transfection to bacteria in vitro. The efficacy of siRNA was determined in a murine model of haematogenous pulmonary infection.

Results: RT–PCR showed that siRNAs significantly inhibited the expression of the coagulase mRNA. The coagulase titres in the siRNA and control groups were 8 and 32, respectively. Measurement of incorporated radioactivity indicated that the siRNAs were delivered into the bacteria. In the murine infection model, in control and siRNA groups, 7.64 ± 0.42 and 6.29 ± 0.23 log cfu/mL (mean ± SEM) MRSA were detected, respectively, showing that there was a significant decrease in the number of viable bacteria in the siRNA group (P < 0.05).

Conclusions: The results show that siRNA inhibited both mRNA expression and the activity of MRSA coagulase in vitro. The in vivo results revealed that the siRNA was effective in reducing the bacterial load in a murine model of haematogenous pulmonary infection. Targeting of coagulase with siRNA appears to be a novel strategy for treating MRSA infections.

Keywords: pathogenesis; pulmonary infections; murine model

Journal Article.  2796 words.  Illustrated.

Subjects: Medical Oncology ; Critical Care

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