Vancomycin heteroresistance caused by unstable tandem amplifications of the vanM gene cluster on linear conjugative plasmids in a clinical Enterococcus faecium

Vancomycin heteroresistance is prone to missed detection and poses a risk of clinical treatment failure. We encountered one clinical Enterococcus faecium strain, SRR12, that carried a complete vanM gene cluster but was determined as susceptible to vancomycin using the broth microdilution method. However, distinct subcolonies appeared within the clear zone of inhibition in the E-test assay, one of which, named SRR12-v1, showed high-level resistance to vancomycin. SRR12 was confirmed as heteroresistant to vancomycin using population analysis profiling and displayed "revive" growth curves with a lengthy lag phase of over 13 hours when exposed to 2-32 mg/L vancomycin. The resistant subcolony SRR12-v1 was found to carry an identical vanM gene cluster to that of SRR12 but a significantly increased vanM copy number in the genome. Long-read whole genome sequencing revealed that a one-copy vanM gene cluster was located on a pELF1-like linear plasmid in SRR12. In comparison, tandem amplification of the vanM gene cluster jointed with IS1216E was seated on a linear plasmid in the genome of SRR12-v1. These amplifications of the vanM gene cluster were demonstrated as unstable and would decrease accompanied by fitness reversion after serial passaging for 50 generations under increasing vancomycin pressure or without antibiotic pressure but were relatively stable under constant vancomycin pressure. Further, vanM resistance in resistant variants was verified to be carried by conjugative plasmids with variable sizes using conjugation assays and S1-pulsed field gel electrophoresis blotting, suggesting the instability/flexibility of vanM cluster amplification in the genome and an increased risk of vanM resistance dissemination.

Medienart:

E-Artikel

Erscheinungsjahr:

2024

Erschienen:

2024

Enthalten in:

Zur Gesamtaufnahme - volume:68

Enthalten in:

Antimicrobial agents and chemotherapy - 68(2024), 5 vom: 02. Mai, Seite e0115923

Sprache:

Englisch

Beteiligte Personen:

Sun, Lingyan [VerfasserIn]
Zhuang, Hemu [VerfasserIn]
Chen, Mengzhen [VerfasserIn]
Chen, Yan [VerfasserIn]
Chen, Yiyi [VerfasserIn]
Shi, Keren [VerfasserIn]
Yu, Yunsong [VerfasserIn]

Links:

Volltext

Themen:

6Q205EH1VU
Anti-Bacterial Agents
Bacterial Proteins
Enterococcus faecium
Heteroresistance
IS1216E
Journal Article
Research Support, Non-U.S. Gov't
VanM genotype
Vancomycin

Anmerkungen:

Date Completed 02.05.2024

Date Revised 04.05.2024

published: Print-Electronic

Citation Status MEDLINE

doi:

10.1128/aac.01159-23

funding:

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

NLM36996151X