Cluster of linezolid-resistant Enterococcus faecium ST117 in Norwegian hospitals

Abstract

A linezolid-resistant, vancomycin-susceptible Enterococcus faecium strain was isolated from 3 patients who had not received linezolid. The first patient was hospitalized in the same hospitals and wards as the 2 following patients. The E. faecium isolates were resistant to linezolid (minimum inhibitory concentration 8–32 mg/l), ampicillin, and high levels of gentamicin. Resistance to linezolid was associated with a G2576T mutation in 23S rDNA. The cfr linezolid resistance gene was not detected. The 3 isolates showed identical DNA fingerprints by pulsed-field gel electrophoresis, belonged to ST117, and harboured virulence genes esp, hyl, acm, efaAfm, srgA, ecbA, scm, pilA, pilB, and pstD typically associated with high-risk E. faecium genotypes. The linezolid-resistant E. faecium high-risk clone caused bacteraemia in the first 2 cancer patients and survived in the hospital environment for more than a year before appearing in the urethral catheter of the third patient.

Keywords::

• Linezolid resistance
• Enterococcus faecium
• cluster
• ST117
• Scandinavia

Acknowledgements

We thank Guido Werner for providing the linezolid-resistant E. faecium strains UW3698, UW3695, UW3936, and UW3939 as well as a cfr-positive Staphylococcus epidermidis.

Declaration of interest: The authors declare no conflict of interest.