Genetic diversity of vancomycinresistant Enterococcus faecium isolated from blood culture in patients with hematological malignancies

Objective. To study the genetic diversity of vancomycin-resistant Enterococcus faecium (VR-E. faecium) isolated from the blood culture in patients with hematological malignancies by multilocus sequence typing (MLST). Materials and Methods. VR-E. faecium isolated from the blood culture in hematological patients in 6 hospitals of 4 Russian cities (2003–2019) were evaluated. Susceptibility to vancomycin was tested by the broth microdilution method (CLSI, 2018). Vancomycin-resistance genes (vanA, vanB) were identified by polymerase chain reaction. Genotyping of VR-E. faecium was performed by MLST. Results. A total of 83 VR-E. faecium were examined. The vanA genes were detected in 71.1% (n = 59) VR-E. faecium, vanB genes – in 28.9% (n = 24). A total of 22 sequence types (STs) belonging to epidemic clonal complex CC17 were detected. The dominant sequence types were ST17 (19.3%), ST78 (18.1%), ST80 (16.9%), and comprised 54.3% VR-E. faecium. Other sequence types included 1 to 4 strains. VR-E. faecium carrying vanA, in comparison with VR-E. faecium vanB, significantly more often belonged to ST78 (23.7% vs. 4.2%, p = 0.0559, respectively) and ST80 (23.7% versus 0%, p = 0.0079, respectively) and less frequently to ST17 (6,8% versus 50%, р < 0.0001). Circulation of 9 STs including «high-risk» clones ST17 and ST78 was detected during two study periods (2003–2011 and 2012–2019). Conclusions. This study showed a genetic diversity of VR-E. faecium that was represented by 22 STs. All VR-E. faecium belonged to epidemic clonal complex CC17 and comprised «high-risk» clones ST17, ST78 and less common STs.