In vitro activity of tigecycline against enterococci
Abstract number: P599
Lesenne A., Aires J., Bourgeois-Nicolaos N., Couzon B., Doucet-Populaire F.
Objectives: This study was undertaken to determine in vitro activity of tigecycline, the first representative of glycylcyclines, against 65 enterococci French isolates and to correlate this activity with their resistance gene content. Moreover, the activity of tigecycline was compared to that of other tetracyclines (tetracycline, minocycline, and doxycycline) and 4 main antibiotics used in the treatment of enterococci infections (amoxicillin, vancomycin, linezolide, quinupristine-dalfoppristine (QP)).
Methods: MICs were determined using the CLSI agar dilution method. We studied 55 clinical isolates of enterococcus of human origin and 10 isolates of animal origin (30 Enterococcus faecalis and 35 Enterococcus faecium) among which 11 strains resistant to glycopeptides (VRE) harbouring the vanA or vanB gene. The presence of the 2 main genes encoding tetracycline resistance in Enterococci: tet (M) (ribosomal protection) and tet (L) (efflux) was detected by PCR on all the strains.
Results: Among the 65 isolates studied, 22, all E. faecium, were resistant to amoxicillin (MIC range 0.12564 mg/L). Only 49% of the strains were susceptible to QP. All the strains were susceptible to linezolide (MIC range 12 mg /L). Among tetracyclines antibiotics, tetracycline was the least active molecule with 41% (n = 27) of susceptible strains (MIC90: 64 mg/L); 46% (n = 30) strains were susceptible to doxycycline (MIC90: = 16 mg/L) and 54% (n = 36) to minocycline (CMI90: 64 mg/L). All the 43 tetracycline resistant strains ((MIC > 8 mg /L) possessed at least one of the 2 genes: tet (L) or tet (M). All the studied strains, whatever their phenotype and genotype of tetracyclines resistance, were highly susceptible to tigecycline with MIC90 equal to 0.125 mg/L (MIC range 0.030.125 mg/L). No difference of susceptibility was observed according to the species and to the phenotype of resistance.
Conclusion: Tigecycline presents a good in vitro activity against E. faecalis and E. faecium including VRE. This activity is not modified in the presence of genes tet (M) and tet (L) the most frequent in Enterococci encoding tetracyclines resistance.
|Session name:||18th European Congress of Clinical Microbiology and Infectious Diseases|
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