Efficacy of tigecycline and vancomycin in experimental catheter-related Staphylococcus epidermidis infection: microbiological and electron microscopic analysis of biofilm

Central venous catheters are frequently used. The commonest cause of catheter-related bloodstream infections (CRBSI) is coagulase-negative staphylococci (CoNS) associated with adherent biofilm. Tigecycline, a derivative of tetracycline, acts against strains producing biofilm. In this study, we aimed to determine the effect of tigecycline in a CRBSI model. A single dose of 108 colony-forming units (CFU)/mL of slime-producing Staphylococcus epidermidis was given through polyethylene catheters inserted into 24 rabbits. After 72 h, groups of eight rabbits were treated with heparin, vancomycin/heparin or tigecycline/heparin. Blood obtained from peripheral veins and the catheter lumen as well as catheter tips were cultured, and three catheters from each group were studied using electron microscopy. Surfaces were randomly subdivided and areas with ≥50 bacteria were compared. Blood cultures were positive from all heparin-treated rabbits but were negative from those receiving either antibiotic (P < 0.001). Catheter tip cultures revealed growth from six, two and one rabbit(s) given heparin, vancomycin and tigecycline, respectively. Electron microscopy showed that catheters from heparin-treated rabbits were most heavily colonised (more areas with ≥50 CFU) compared with catheters from animals treated with vancomycin or tigecycline (P < 0.003 and P < 0.001, respectively). In conclusion, this study shows that tigecycline and vancomycin are both effective for treating CRBSI due to CoNS. Electron microscopy of catheters themselves suggests that tigecycline is superior to vancomycin (P < 0.001). Tigecycline may be useful for the treatment of CRBSI.