Genomic features and instability of linezolid resistance in vancomycin-resistant Enterococcus faecalis ST525

In Brazilian clinical Enterococcus faecalis ST525 LVRE isolates, linezolid MICs vary (8–32 mg/L) despite only G2576T and G2505A rrl mutations, with resistance stability differing by starting MIC.

• Why it matters: The lineage is poorly characterized and reported as VRE or LVRE in hospitals, yet how its oxazolidinone resistance persists and shifts without drug pressure is unclear.
• What they did: Five ICU LVREfs underwent serial in vitro passages without antibiotics, tracking linezolid MIC changes and rrl copy reversion; one isolate (LVREfs L7) was analyzed by whole-genome sequencing.
• The result: Isolates starting at 8–16 mg/L showed progressive MIC reductions with rrl reversion, while the 32 mg/L isolate maintained high-level resistance; WGS found a ~2.8-Mb chromosome enriched in mobile elements (~8.6%) and a plasmid-borne vanA prototype Tn1546 inserted into a Tn3-family transposase gene, suggesting potential challenges for routine susceptibility testing.

AI summary of the abstract · may contain errors · not medical advice · read the paper.