Rapid Plasmid-Mediated Acquisition of Erythromycin Resistance via ermX in Corynebacterium striatum: A 72-Hour Clinical Evolution.

PURPOSE: To investigate the genomic mechanisms driving rapid erythromycin resistance emergence in Corynebacterium striatum during clinical management of urinary tract infections.

METHODS

Longitudinal analysis of four C. striatum isolates (C1-C4) from an ICU patient with candida coinfection was conducted using CLSI M45-A3-guided microbroth dilution and comparative whole-genome sequencing. Phylogenetic reconstruction (27 housekeeping genes) confirmed clonal origin, while CARD/PIPdb/ISfinder databases characterized resistome dynamics.

RESULTS

Erythromycin susceptibility shifted from susceptible (minimum inhibitory concentration, MIC ≤ 0.25 μg/mL) to resistant (MIC = 4 μg/mL) within 72 hours, correlating with acquisition of a plasmid carrying ermX flanked by ISL3-family elements (ISCx1).

CONCLUSION

This first documentation of sub-72-hour ermX plasmid acquisition in C. striatum highlights critical infection control challenges in ICU settings. We recommend daily antimicrobial susceptibility testing (AST) profiling for C. striatum in ICU patients receiving macrolides, coupled with PCR screening for ermX to preempt resistance dissemination.