Activity of tigecycline tested against vancomycin-resistant enterococci, including clonal complex-17 E. faecium strains, isolated in Europe

Abstract number: P1728

Sader H., Fritsche T., Jones R.

Objectives: To evaluated the activity of tigecycline when tested against clinical strains of enterococci collected in European medical centres, including E. faecium strains characterised as being clonal complex 17 (CC-17).CC-17 characterizes a lineage of E. faecium with resistance (R) to ampicillin (AMP) and ciprofloxacin (CIP) with or without R to vancomycin (VANC), a pathogenicity island and an association with hospital outbreaks, which have spread globally.

Methods: Enterococcal strains were submitted from 34 medical centres located in Europe (13 countries) and Israel during 2000–2007. Strains were susceptibility (S) tested against tigecycline and >20 antimicrobials using CLSI broth microdilution methods and US-FDA/EUCAST interpretative criteria (tigecycline S at 0.25 mg/L). VanA E. faecium strains R to AMP and CIP were characterised as a CC-17. A subset of CC-17 strains were further characterised by PFGE and PCR for esp gene.

Results: 4,591 enterococcal strains (7.1% VANC-R) were collected, including 3,070 E. faecalis (1.6% VANC-R) and 1,337 E. faecium (22.3% VANC-R). VANC-R was observed in 27 (79.4%) centres (all countries surveyed). Higher rates of VANC-R were found in Germany, Ireland and the United Kingdom. High level gentamicin R was observed in 33.3% of E. faecalis and 40.9% of E. faecium, while only 73.5% of E. faecium were S to quinupristin/dalfopristin. Tigecycline was very active against enterococci (MIC90, 0.25 mg/L; 97.3% S), including VANC-R E. faecium (MIC90, 0.12 mg/L; 99.7% S) and E. faecalis (MIC90, 0.25 mg/L; 94.0% S) strains (see Table). Tigecycline was also highly active against VANC-R E. faecium CC-17 phenotype strains (MIC90, 0.12 mg/L; 100.0% S).

Conclusions: Tigecycline was very active against strains of enterococci causing infections in European hospitals and its activity was not adversely affected by R to VANC or other antimicrobials. This novel glycylcycline represents an important therapeutic option for infections caused by vancomycin-resistant enterococci, including the epidemic E. faecium CC-17 strains.