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Antimicrobial Agents and Chemotherapy, June 2008, p. 2205-2211, Vol. 52, No. 6
0066-4804/08/$08.00+0     doi:10.1128/AAC.01340-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

RNAIII-Inhibiting Peptide Enhances Healing of Wounds Infected with Methicillin-Resistant Staphylococcus aureus

Department of Dermatology,¹ Institute of Infectious Diseases and Public Health,² Department of General Surgery, I.N.R.C.A.-I.R.R.C.S,³ Institute of Pathology,⁴ Department of Plastic and Reconstructive Surgery General Surgery, Università Politecnica delle Marche, Ancona, Italy,⁵ Experimental Animal Models for Aging Units, Research Department, I.N.R.C.A.-I.R.R.C.S., Ancona, Italy,⁶ Department of Biomedical Sciences, Cummings School of Veterinary Medicine, Tufts University, North Grafton, Massachusetts 01536⁷

Received 18 October 2007/ Returned for modification 26 November 2007/ Accepted 26 March 2008

Quorum sensing is a mechanism through which a bacterial population receives input from neighboring cells and elicits an appropriate response to enable survival within the host. Inhibiting quorum sensing by RNAIII-inhibiting peptide (RIP) has been demonstrated as a very effective mode of prevention and therapy for device-associated staphylococcal infections and was tested here for healing of wounds that are otherwise resistant to conventional antibiotics. Wounds, established through the panniculus carnosus of BALB/c mice, were inoculated with 5 x 10⁷ CFU of methicillin-resistant Staphylococcus aureus. Mice were treated with Allevyn, RIP-soaked Allevyn (containing 20 µg RIP), daily intraperitoneal teicoplanin (7 mg/kg of body weight), Allevyn and teicoplanin, and RIP-soaked Allevyn and daily intraperitoneal teicoplanin. The main outcome measures were quantitative bacterial culture and histological examination with assessment of microvessel density and of vascular endothelial growth factor (VEGF) expression in tissue sections. Treatment with RIP-soaked Allevyn together with teicoplanin injection greatly reduced the bacterial load to 13 CFU/g (control untreated animals had 10⁸ CFU/g bacteria). All other treatments were also significantly effective but only reduced the bacterial load to about 10³ CFU/ml. Histological examination indicated that only treatment with RIP-soaked Allevyn with teicoplanin injection restored epithelial, granulation, and collagen scores, as well as microvessel density and VEGF expression, to the levels found with uninfected mice. In conclusion, we observed that RIP may be useful for the management of infected wounds and that it could represent an exciting and future alternative to the conventional antibiotics, at present considered the gold-standard treatments for methicillin-resistant S. aureus infections.

Published ahead of print on 7 April 2008.