In vitro evaluation of tigecycline against 261 recent isolates of vancomycin-resistant Enterococci C T.E.S.T. Program 2006

Abstract number: p488

Johnson  B., Bouchillon  S., Stevens  T., Johnson  J., Hoban  D., Dowzicky  M.

Background: 

Tigecycline (TIG), a member of a new class of antimicrobials (glycylcyclines), has been shown to have potent expanded broad spectrum activity against most commonly encountered species responsible for community and hospital acquired infections. The T.E.S.T. program determined the in vitro activity of tigecycline compared to amoxicillin-clavulanic acid, piperacillin-tazobactam, levofloxacin, ceftriaxone, linezolid (LZD), minocycline, vancomycin (VAN), ampicillin (AM), penicillin, and imipenem against VRE collected from hospitals globally throughout 2004–2006.

Methods: 

261 VRE (52 Enterococcus faecalis, 209 E. faecium) clinical isolates were identified to the species level at each participating site and confirmed by the central laboratory. Minimum Inhibitory Concentrations (MICs) were determined by the local laboratory using supplied broth microdilution panels and interpreted according to CLSI guidelines with tigecycline susceptible breakpoint defined as < 0.25 mg/mL.

Results: 

Percentage susceptible of all VRE to TIG, LZD, and MIN were 99.2, 94.6, and 62.9, respectively. For E. faecalis strains, the three most active drugs were TIG (98.1%), LZD (97.1%), and AM (96.7%). For E. faecium, the three most active drugs were TIG (99.1%), LZD (95.6%), and MIN (69.1%). There were significant differences in VRE rates between North America (E. faecalis 5.2%, E. faecium 66.7%), Europe (E. faecalis 2.4%, E. faecium 12.5%), Middle East (E. faecalis 0%, E. faecium 9.1%), Latin America (E. faecalis 20%, no E. faecium) and Asia (E. faecalis 0%, E. faecium 9.1%).

Conclusions: 

TIG exhibited outstanding activity against VRE, inhibiting 100% of strains with MICs <=0.5 mg/ml (MIC90 = 0.12), surpassing LZD as the most active drug in this study. The exceptionally broad spectrum of TIG, which includes many other multi-resistant gram-positive and gram-negative bacteria in addition to VRE, will make it an attractive addition to hospital formularies.