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. 2018 May;38(3):226-234.
doi: 10.3343/alm.2018.38.3.226.

Comparison of Enterococcus faecium Bacteremic Isolates from Hematologic and Non-hematologic Patients: Differences in Antimicrobial Resistance and Molecular Characteristics

Sung Yeon Cho  1   2   3 , Yeon Joon Park  4 , Hanwool Cho  5 , Dong Jin Park  5 , Jin Kyung Yu  5 , Hayeon Caitlyn Oak  6 , Dong Gun Lee  1   2   3
Affiliations

Comparison of Enterococcus faecium Bacteremic Isolates from Hematologic and Non-hematologic Patients: Differences in Antimicrobial Resistance and Molecular Characteristics

Sung Yeon Cho et al. Ann Lab Med. 2018 May.

Abstract

Background: Enterococcus faecium, especially vancomycin-resistant E. faecium (VREfm), is a major concern for patients with hematologic diseases. Exposure to antibiotics including fluoroquinolone, which is used as a routine prophylaxis for patients with hematologic (MH) diseases, has been reported to be a risk factor for infection with vancomycin-resistant eneterocci. We compared the characteristics of E. faecium isolates according to their vancomycin susceptibility and patient group (MH vs non-MH patients).

Methods: A total of 120 E. faecium bacteremic isolates (84 from MH and 36 from non-MH patients) were collected consecutively, and their characteristics (susceptibility, multilocus sequence type [MLST], Tn1546 type, and the presence of virulence genes and plasmids) were determined.

Results: Among the vancomycin-susceptible E. faecium (VSEfm) isolates, resistance to ampicillin (97.6% vs 61.1%) and high-level gentamicin (71.4% vs 38.9%) was significantly higher in isolates from MH patients than in those from non-MH patients. Notably, hyl, esp, and pEF1071 were present only in isolates with ampicillin resistance. Among the VREfm isolates, ST230 (33.3%) and ST17 (26.2%) were predominant in MH patients, while ST17 (61.1%) was predominant in non-MH patients. Plasmid pLG1 was more prevalent in E. faecium isolates from MH patients than in those from non-MH patients, regardless of vancomycin resistance. Transposon analysis revealed five types across all VREfm isolates.

Conclusions: The antimicrobial resistance profiles and molecular characteristics of E. faecium isolates differed according to the underlying diseases of patients within the same hospital. We hypothesize that the prophylactic use of fluoroquinolone might have an effect on these differences.

Keywords: Ampicillin; Enterococcus; Fluoroquinolone; Multilocus sequence typing; ST230; pEF1071; pLG1.

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Conflict of interest statement

The authors declare that they have no conflicts of interest related to this study.

Figures

Fig. 1
Fig. 1. Distribution of VSEfm and VREfm sequence types in MH and non-MH patients. (A) STs of VSEfm isolated from MH patients. (B) STs of VSEfm isolated from non-MH patients. (C) STs of VREfm isolated from MH patients. (D) STs of VREfm isolated from non-MH patients.
“Others” comprises single individual STs. Abbreviations: MH, hematologic patients; non-MH, non-hematologic patients; ST, sequence type; VREfm, vancomycin-resistant E. faecium; VSEfm, vancomycin-susceptible E. faecium.
Fig. 2
Fig. 2. Population snapshot by eBURST analysis (http://eburst.mlst.net) showing clusters of linked and unlinked sequence types (STs) identified in this study. The boxed numbers represent sequence types.
Fig. 3
Fig. 3. Genetic maps of Tn1546 in vancomycin-resistant Enterococcus faecium bacteremic isolates. The positions of genes and open reading frames and the direction of transcription are marked by arrows. Inverted triangles represent insertion sequence (IS) elements. Dotted lines indicate deletions.
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