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Efficacy of linezolid in the treatment of biofilm-associated infection using a rabbit model of methicillin-resistant Staphylococcus aureus catheter biofilm

Abstract number: 1732_126

Ghannoum M., Long L., Kim H., Rotondo V., Cirino A., Sheehan D.

Objectives: Catheter-related biofilm infections (CRBI) are a major cause of bloodstream infections in the USA. One of the most common causes of CRBI related bloodstream infection is methicillin-resistant Staphylococcus aureus (MRSA). Catheter removal has become an integral part of the therapeutic approach to CRBI, however, it is associated with increased medical costs, potential morbidity, and is not always feasible in critically ill patients. Antibiotic lock therapy provides the means for local delivery of high drug concentrations to overcome resistance due to bacterial biofilms that coat the catheter surface. In this in vivo study, we compared the effectiveness of linezolid (LIN) versus vancomycin (VAN) antibiotic lock therapy against MRSA CRBI.

Methods: In New Zealand White rabbits, silicone catheters were tunneled subcutaneously and surgically placed in their jugular vein. The catheter lumen was infected by locking 1×107 MRSA in the lumen for 24 h. To maintain catheter patency, heparin flushes were performed daily. Rabbits were randomised into three groups: untreated control, VAN 2 mg, and LIN 2 mg. Each drug was locked in the catheter lumen for 8 h a day for 7 days. After treatment, the animals were anaesthetised and peripheral blood cultures were taken from the catheter. Animals were sacrificed, catheter removed and divided into two pieces; one piece for quantitative culture and the other for scanning electron microscopy (SEM).

Results: Biofilms were confirmed by blood culture showing MRSA growth from the catheter 3 days post-infection. Catheters removed from untreated controls yielded a higher fungal burden than LIN and VAN-treated groups (2.59±0.76, 0.20±0.08, and 0.18±0.68, respectively). No significant difference was observed between LIN and VAN treatment groups, (P value 0.8764). SEM of untreated control catheters revealed patchy, abundant biofilms while both LIN and VAN treated catheters had almost completely cleared surfaces. VAN-treated catheters had small patches of bacteria with damaged biofilm matrix, while LIN-treated catheters had scattered patches of bacteria with little or no surrounding matrix.

Conclusion: Antibiotic lock therapy with LIN may be a useful treatment strategy against MRSA in CRBI's. A prospective, randomised clinical trial evaluating LIN for the treatment of MRSA caused CRBI is warranted.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Subject:
Location: ICC, Munich, Germany
Presentation type:
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