Emergence of Dual β-lactam and Colistin Resistance via bla FRI-8 and mcr-10.2 co-carriage on an IncFII Family Plasmid in Enterobacter vonholyi
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Objectives
Enterobacter vonholyi isolate E323169 represents a rare case of co-carriage of the antimicrobial resistance genes (ARGs) bla FRI-8 , mcr-10 . 2 . isolated from a clinical rectal swab. E323169 is one of only 12 available E. vonholyi genomes. To date, and across over two million pathogenic genomes scanned, only three harbour bla FRI-8 and two encode mcr-10 . 2 , yet none exhibit both genes together. This study analyzes the genomic, phenotypic and epidemiological importance of this rare co-occurrence.
Methods
Species-ID for E323169 was assigned by MALDI-TOF and then re-assigned and confirmed using a multifactorial genomic workflow. Antimicrobial susceptibilities were determined by MIC assay. The genome of E323169 was sequenced on an Illumina-NextSeq-1000, assembled, and annotated for ARGs, virulence factors, and plasmid replicons detection. Comparative phylogenomics used 12 E. vonholyi RefSeq assemblies, and NCBI metadata were analysed for plasmid distributions of bla FRI-8 and mcr-10 . 2 .
Results
E323169 carried six ARGs: four chromosomally encoded ( blaACT-91, fosA, oqxA10, oqxB9 ) and two plasmid-borne ( bla FRI-8 and mcr-10 . 2 ) co-located on IncFII(p14)_1_p14 replicon. Additional plasmid replicons: Col(MG828)_1 and ColRNAI_1 were also identified. By mining the NCBI Pathogen Detection pipeline, we identified bla FRI-8 on IncFII replicon in E. asburiae JBIWA002, and mcr-10 . 2 on a multi-replicon (IncFIB/IncFII) plasmid in E. kobei 11778-yvys.
Conclusion
This report documents the first E. vonholyi isolate co-harboring bla FRI-8 and mcr-10 . 2 on a single IncFII family plasmid, showing the widening host range of plasmid-mediated resistance to carbapenems/colistin. No prior similar co-occurrences reported, underscoring its rarity. These findings highlight the urgent need for enhanced clinical screening and genomic surveillance to curb the spread.
