Identification of risk factors for long-term persistence of linezolid resistant enterococci - experiences from a tertiary care centre

Introduction

Linezolid-resistant enterococci (LRE) have raised concern worldwide due to their increased detection in healthcare settings. Infections are often preceded by colonisations and intensified infection prevention and control strategies are established to minimize spreading. As specific eradication strategies are lacking, these precautions are often continued until spontaneous clearance occurs. However, LRE may persist over long periods of time. Here we aim at identifying factors determining a prolonged colonisation.

Materials & Methods

Patients that were admitted on an intensive care unit, oncological or infectious disease ward at a tertiary care hospital were screened for LRE via rectal swab during one year study period. Patients colonized for more than ten weeks were defined as long-term carriers. LRE-isolates were subjected to whole genome sequencing and compared using a core genome Multilocus Sequencing Typing approach. Demographic and clinical risk factors of admitted patients were recorded.

Results

In the study period, 77 patients colonized with LRE (59 LR E. faecium, 18 LR E. faecalis) were identified. Of these, 30 (39%) were female. The median age was 65 years (range 23-90 years). Of all patients, 9 (12%) were LRE long-term carriers according to above mentioned classification. Spontaneous LRE clearance was observed in 40 patients (52%). Comparison of risk factors in the LRE persistence vs. clearance group resulted in liver dysfunction being significantly more often associated with LRE persistence (p=0.03). Other clinical or demographic factors did not differ significantly between both groups. Assessment of genetic relatedness of detected LRE revealed 7 clusters comprising 1-12 genotypes of LR E. faecium and 4 clusters comprising 2 genotypes of LR E. faecalis.

Summary

First results of our study suggest that persistence of LRE colonisation is potentially overestimated. Long-term-colonisation is favoured by patient associated risk factors, whereby liver dysfunction plays a relevant role. Genetically, the LRE isolates of this study show a high diversity, revealing that LRE are rather acquired due to antibiotic treatment than by transmission.