bCentral venous catheters commonly develop central line-associated bloodstream infections. In vitro antibiotic lock therapy (ALT) was simulated on 10 methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates imbedded in biofilm-coated silicon disks. Five days of 4-h daily exposures to daptomycin (2.5 mg/ml) in 25% ethanol or minocycline (3 mg/ml) plus 25% ethanol and 30 mg/ml EDTA resulted in significantly greater elimination of MRSA colonization than treatment with minocycline alone.
Of the 5 million central venous catheters (CVCs) inserted annually, an estimated 80,000 are associated with central lineassociated bloodstream infections (CLABSIs) (1). CLABSIs are an independent risk factor for increased hospital costs and length of stay. There are four recognized routes for contamination of CVCs: (i) migration of organisms colonizing the skin at the insertion site into the catheter tract, along the catheter surface, and consequently colonization of the catheter tip (2-4); (ii) direct contamination of the catheter/catheter hub through contact with hands, contaminated fluids, or contaminated devices (5, 6); (iii) hematogenous seeding from another focus of infection (7); and (iv) rarely, contamination of intravenous infusate solutions (8). The microorganisms most commonly associated with CVC infection are Staphylococcus aureus (including methicillin-resistant S. aureus [MRSA]) and coagulase-negative staphylococci (CoNS) (9-11). Within 24 h of CVC insertion, host proteins coat the catheter, forming a conditioning film in which microorganisms may bind, forming three-dimensional extracellular structures colonizing the lumen of the CVC. Organisms embedded in this biofilm are usually refractory to treatment with systemic antibiotic therapy alone (6, 12). These organisms have reduced susceptibility to antimicrobial agents in the range of 10-to 1,000-fold compared to planktonic cells (13).Published CLASBI guidelines recommend that infected longterm CVCs be removed if associated with severe sepsis, suppurative thrombophlebitis, endocarditis, bloodstream infection that continues despite 72 h of antimicrobial therapy to which the infecting microbes are susceptible, or infections due to S. aureus and that short-term CVCs be removed from patients with CLABSIs due to S. aureus (14). Unfortunately, on occasion, clinical circumstances may preclude removing the CVC for reasons of safety or feasibility. Antibiotic lock therapy (ALT) involves instilling a highly concentrated antibiotic solution into a catheter lumen and allowing the solution to dwell for a specified time period for the purpose of sterilizing the lumen and salvaging the CVC. In conjunction with systemic antimicrobial agents, ALT is indicated for CLABSIs involving long-term catheters with no signs of exit site or tunnel infection with the goal of catheter salvage.Daptomycin, a novel lipopeptide antibiotic, has potent bactericidal activity in vitro against most clinically important Grampositive pathogens, including MRSA, CoNS, vancomycin-resistant enterococci...