Duration of hospitalization increases the risk for long-term carriage of linezolid-resistant enterococci in critically ill patients.

Background: Enterococci are gut commensal microorganisms, which can however cause life-threatening infections especially in patients suffering from intestinal barrier disorders. Treatment of these enterococcal infections is challenging due to a variety of intrinsic and acquired antibiotic resistances. In this context, linezolid is applied as last-resort antibiotic. Our study aimed at determining linezolid-resistant enterococci (LRE) long-term carriage (≥ 10 weeks), since this is a risk factor for the development of LRE infection.

Methods: In a one-year cohort study, all patients on hemato-oncology, intensive and intermediate care units were screened for LRE. To determine the molecular epidemiology, all detected LRE isolates were subjected to whole genome sequencing-based typing to investigate whether in-host selection or pathogen transmission was causative for LRE occurrence. Clinical and demographic data were recorded to identify risk factors for LRE clearance and persistence.

Results: Long-term LRE carriage was identified in 7 of 46 (15%) patients. Duration of hospitalization differed significantly between LRE persistence (mean: 110 days; range 28-225 days) and clearance group (mean: 53 days; range 5-213 days). LRE strains mostly exhibited a high genetic core genome diversity, indicating that transmission events played a minor role.

Conclusions: Our study shows that the duration of hospitalization increases the risk for long-term carriage of LRE. In contrast to other multi drug resistant bacteria, LRE carriage was rarely caused by transmission events. Thus, future infection prevention measures should focus on antimicrobial stewardship approaches next to classical hygiene strategies.