Efficacy of Tigecycline and Rifampin Alone and in Combination against Enterococcus faecalis Biofilm Infection in a Rat Model of Ureteral Stent

Abstract

We investigated the efficacy of tigecycline and rifampin alone or combined in preventing ureteral stent infection due to Enterococcus faecalis. The activities of the two antibiotics were previously studied in vitro in absence or in presence of biofilm. For in vivo research, the study included a control group without bacterial challenge to evaluate the sterility of surgical procedure, a challenged control group that did not receive any antibiotic prophylaxis and, for each bacterial strain, three challenged groups that received: (1) 2 mg/kg intraperitoneal tigecycline, immediately after stent implantation; (2) rifampin-coated ureteral stents where 0.2 cm(2) sterile ureteral stents were incubated in 10 mg/L rifampin solution for 30 min immediately before implantation; and (3) intraperitoneal tigecycline plus rifampin-coated ureteral stent at the above concentrations. Ureteral stents were explanted at d 5 following implantation and biofilm bacteria enumerated. The in vitro studies showed that the biofilm was strongly affected by the presence of rifampin and, in its presence, tigecycline had MICs and MBCs lower than those obtained in the absence of rifampin. Intraperitoneal tigecycline exerted stronger effect than rifampin on bacterial numbers. The combination rifampin plus tigecycline showed efficacies higher than that of each single compound. These results highlight the potential usefulness of tigecycline in preventing enterococcal ureteral stent infections and the role of rifampin as an interesting antibiotic enhancer.