Lack of antimicrobial activity of sodium heparin for treating experimentalcatheter-related infection due to Staphylococcus aureus using the antibiotic-lock technique

Objective To elucidate the potential antimicrobial activity of sodium hepar in in the treatment of catheter infection using the antibiotic-lock techniq ue. Methods We performed in vitro studies of the antibiotic susceptibility, sta bility and synergy of sodium heparin, vancomycin and ciprofloxacin. Efficac y studies were performed in a new animal model of Staphylococcus aureus cat heter-related infection in which infection was produced via the endoluminal route. White New Zealand rabbits were surgically implanted with a sylastic catheter into the inferior cava vein. Immediately afterwards. infection wa s induced by filling and locking the catheters with 0.7 ml of broth culture containing 10(8) colony-forming units of S. aureus. Eighteen hours later t he antibiotic-lock technique was started. Treatment groups were: control wi thout treatment, sodium heparin at 2500 IU/mL, vancomycin at 2500 mg/L, cip rofloxacin at 1000 mg/L, vancomycin plus heparin and ciprofloxacin plus hep arin. Results Sodium heparin showed an MIC90 higher than 6000 UI/mL against S. au reus causing catheter infection. Studies of antimicrobial synergy by the ti me-kill method between vancomycin and ciprofloxacin at MIC with sodium hepa rin at 2500 IU/mL showed no interactions. Vancomycin (2000 mug/mL) and cipr ofloxacin (1000 mug/mL) in a solution containing sodium heparin (2500 IU/mL ) were stable at 37 degreesC for a 72-h period. Two sets of in vivo experim ents were carried out using differents strains of S. aureus. In both cases. sodium heparin showed no therapeutic efficacy when compared to control gro up and did not increase the antibiotic efficacy when used in combination wi th vancomycin or ciprofloxacin. Conclusion Sodium heparin lacked antibacterial activity against S. aureus c ausing catheter-related infections.