Analysis of methods commonly used for glycopeptide and oxazolidinone susceptibility testing in Enterococcus faecium isolates.
The susceptibility to teicoplanin, vancomycin and linezolid of 30 clinical isolates of Enterococcus faecium was tested by Vitek 2, Phoenix, Etest, broth microdilution and disc diffusion tests. The vanA and vanB resistance genes and the 23S rRNA gene G2576T mutation were detected by PCR and PCR-RFLP, respectively. Resistance rates to teicoplanin ranged from 3% for Vitek 2 to 57.6% for the Phoenix test, and those to vancomycin ranged from 56.7% for Vitek 2 to 86.7% for the Phoenix test. Only two out of 25 strains carrying the vanA gene were univocally recognized as the VanA phenotype. The only strain with the G2576T mutation did not carry the vanA gene and showed resistance to linezolid by the disc diffusion, Vitek 2 and broth dilution methods (MIC>8 microg ml(-1)), but was susceptible when tested with the Phoenix test and Etest (MIC<or=4 microg ml(-1)). Therefore, the resistance to glycopeptides and linezolid was not univocally detected by the susceptibility testing methods used in this study.
Raponi
Giammarco
G
Dipartimento di Scienze di Sanità Pubblica, 'Sapienza' University of Rome, Rome, Italy.
Ghezzi
Maria Cristina
MC
Dipartimento di Scienze di Sanità Pubblica, 'Sapienza' University of Rome, Rome, Italy.
Gherardi
Giovanni
G
Dipartimento di Scienze Biomediche, 'Campus Bio-Medico' University, Rome, Italy.
Lorino
Giulia
G
Dipartimento di Scienze di Sanità Pubblica, 'Sapienza' University of Rome, Rome, Italy.
Dicuonzo
Giordano
G
Dipartimento di Scienze Biomediche, 'Campus Bio-Medico' University, Rome, Italy.
D000081:Acetamides / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D019729:Carbon-Oxygen Ligases / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D016984:Enterococcus faecium / Q000187:drug effects*; D006020:Glycopeptides / Q000494:pharmacology*; D006801:Humans; D000069349:Linezolid; D008826:Microbial Sensitivity Tests / Q000379:methods; D023303:Oxazolidinones / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012338:RNA, Ribosomal, 23S / Q000235:genetics; D017334:Teicoplanin / Q000494:pharmacology; D014640:Vancomycin / Q000494:pharmacology
D000081:Acetamides; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D006020:Glycopeptides; D023303:Oxazolidinones; D012338:RNA, Ribosomal, 23S; C071437:VanA ligase, Bacteria; C079913:VanB protein, Enterococcus; D017334:Teicoplanin; D014640:Vancomycin; D019729:Carbon-Oxygen Ligases; D000069349:Linezolid