Microbial inactivation properties of a new antimicrobial/antithrombotic catheter lock solution (citrate/methylene blue/parabens)

BACKGROUND Microbial infections are the most serious complications associated with indwelling central venous catheters. A catheter lock solution that is both antibacterial and antithrombotic is needed. The goal of this study was to determine whether a new catheter lock solution containing citrate, methylene blue and parabens has antimicrobial properties against planktonic bacteria and against sessile bacteria within a biofilm. These effects were compared to the antimicrobial properties of heparin at 2500 units/ml. METHODS The tested solution (C/MB/P comprising 7% sodium citrate, 0.05% methylene blue and 0.165% parabens) and individual components were challenged against gram-positive and gram-negative organisms and fungi. Control solutions were heparin with preservatives. Studies included evaluation of eradication of planktonic bacteria and sessile organisms in a biofilm grown on polymeric and glass coupons. Biofilm samples were inspected by scanning electron microscopy, atomic force microscopy and vital stains. RESULTS The C/MB/P solution, contrary to heparin, kills most tested planktonic microorganisms within 1 h of incubation. All tested organisms have an MIC of 25% or less of the original concentration of a new catheter lock. Bacteria strains did not develop resistance over more than 40 passages of culture suspensions. The C/MB/P solution is able to kill nearly all sessile bacteria in biofilm growth on plastic or glass discs in 1 h. Microscopic methods demonstrated extensive physical elimination of biofilm deposits from treated coupons. In contrast, heparin had a minimal effect on planktonic or biofilm organisms. CONCLUSIONS The new multicomponent lock solution has strong antimicrobial properties against both planktonic and sessile microorganisms. By comparison, heparin with preservative has weak antibacterial properties against planktonic and biofilm bacteria. The tested catheter lock may have usefulness in preventing bacterial colonization of haemodialysis catheters and diminishing the incidence of catheter-related bacteraemia.