Klebsiella pneumoniae continues to be an importantcause ofcommunity-acquired and nosocomial infection. This bacterium can cause catheterrelated infections by forming biofilmon the surface of catheter. The aim of our study is to determine the in vitro stability and efficacy of colistin, ciprofloxacin, tobramycin, doripenem and tigecycline alone, or in combination with clarithromycin or esomeprazole, as 24-h lock solutions against biofilm-embedded K. pneumoniae strains. The efficacy of antibiotic lock solutions was tested in an in vitro catheter biofilm model against K. pneumoniae. In our study, we observed that the use of doripenem and tobramycin as a lock solution had potent bactericidal effects. When colistin was used in combination with clarithromycin or esomeprazole, the combinations had a synergistic effect. No antagonistic effect was observed. The findings of our study have important information for effectiveness of tested antibiotic lock solution in the catheter-related infections with K. pneumoniae.