In vitro effectiveness of the antibiotic lock technique (ALT) for the treatment of catheter-related infections by Pseudomonas aeruginosa and Klebsiella pneumoniae

Objectives: To determine the adequate antibiotic treatment, the concentration of antibiotics and the duration of treatment with the antibiotic lock technique (ALT) for treatment of central venous catheter-related infections caused by Klebsiella pneumoniae and Pseudomonas aeruginosa. Methods: To investigate the in vitro effectiveness of four candidate antibiotics, amikacin, ceftazidime, cefepime and ciprofloxacin, two isolates of both K. pneumoniae and P. aeruginosa forming biofilms were selected. The polyurethane (PU) films were incubated for 5 days to allow for bacterial colonization or biofilm production. After 5 days, the biofilm-formed PU films were exposed to each of the antibiotics (1, 5 and 10 mg/mL) for 1, 3, 5, 7, 10 and 14 days. The presence of the remaining bacteria in the biofilm was evaluated by the determination of viable cell counts. Results: All of the antibiotic treatments effectively removed P. aeruginosa biofilm within 3 - 5 days. Among the four antimicrobial agents tested in this study, ciprofloxacin showed superior bactericidal activity. The biofilms of both species were eliminated by 5 mg/mL ciprofloxacin within 3 days. In all cases, P. aeruginosa strains were removed more rapidly than K. pneumoniae strains. All antibiotics eradicated the susceptible K. pneumoniae strain, K144, within 5 days. One strain of K. pneumoniae, K139, which was resistant to all tested antibiotics, was not eradicated by amikacin (1, 5 and 10 mg/mL) or 1 mg/mL ceftazidime. Conclusions: These results show that ciprofloxacin, cefepime, ceftazidime and amikacin might be used as an effective ALT for treatment of catheter-related infections caused by antibiotic-susceptible K. pneumoniae and P. aeruginosa. This study suggests that the duration of treatment against catheter-related infection by Gram-negative bacilli can be reduced to 3 - 5 days when using antibiotics to which the organisms are susceptible in vitro, even at a concentration of 1 mg/mL.