RNAIII-inhibiting peptide significantly reduces bacterial load and enhances the effect of antibiotics in the treatment of central venous catheter-associated Staphylococcus aureus infections

Oscar Cirioni, Andrea Giacometti, Roberto Ghiselli, Giorgio Dell'Acqua, Fiorenza Orlando, Federico Mocchegiani, Carmela Silvestri, Alberto Licci, Vittorio Saba, Giorgio Scalise, Naomi Balaban

Research output: Contribution to journalArticle


Background. Medical devices used in clinical practice are often associated with biofilm-associated staphylococcal infections. Methods. An in vitro antibiotic susceptibility assay of Staphylococcus aureus biofilms using 96-well polystyrene tissue-culture plates was performed to test the effects of RNAIII-inhibiting peptide (RIP), ciprofloxacin, imipenem, and vancomycin. Efficacy studies were performed using a rat model of central venous catheter (CVC)-associated infection. Twenty-four hours after implantation, the catheters were filled with RIP (1 mg/mL). Thirty minutes later, rats were challenged, via the CVC, with 1.0 × 106 cfu of S. aureus strain Smith diffuse. The antibiotic-lock technique was begun 24 h later. Results. Minimum inhibitory concentrations of antibiotics in biofilms were at least 4-fold higher than those against the freely growing planktonic cells. When they were first treated with RIP, the cells in biofilms became as susceptible to antibiotics as did planktonic cells. These data were confirmed by the in vivo studies. In particular, when CVCs were treated with both RIP and antibiotics, the biofilm bacterial load was further reduced to 1 × 101 cfu/mL, and bacteremia was not detected, suggesting that there was 100% elimination of bacteremia and a 6 log10 reduction in biofilm bacterial load. Conclusion. RIP significantly reduces bacterial load and enhances the effect of antibiotics in the treatment of CVC-associated S. aureus infections.

Original languageEnglish
Pages (from-to)180-186
Number of pages7
JournalJournal of Infectious Diseases
Issue number2
Publication statusPublished - Jan 15 2006


ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health
  • Immunology

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