Investigation of Various Antibiotics Alone and Combined with Clarithromycin as Lock Solutions on Eradication of Biofilms Strains Belonging to Enterobacterales

Antibiotic lock solutions is recommended as an adjunctive therapy for patients who have catheter
related bloodstream infections. The aims of our study is, to determine the in-vitro efficacy of colistin,
ciprofloxacin, tobramycin, and doripenem alone or in combination with clarithromycin as 24 hour lock
solutions against biofilm-embedded Enterobacterales (Escherichia coli and Enterobacter cloacae)
strains. The efficacy of antibiotic lock solutions was tested in an in-vitro catheter biofilm model against
two E. coli and two E. cloacae isolated from catheter tip, respectively. In our study, we observed that
the use of doripenem and tobramycin as a lock solution had potent bactericidal effects (> 3 log10
reduction). When colistin was used in combination with clarithromycin, the combination showed
synergistic activity for one E. cloacae strain. Tobramycin, doripenem, and ciprofloxacin were used in
combination with clarithromycin, the combinations had same effect on all strains comparatively with
these antibiotics alone. No antagonistic effect was observed. The findings of our study have important
informations for effectiveness of tested antibiotic lock solution with these antibiotics alone or in
combination in the catheter related infections with belonging to Enterobacterales. Further
investigations are needed to alternative treatment options for catheter related infections that were
caused by Enterobacterales