Investigation of a pseudo-outbreak of Myroides odoratimimus in high-dependency units reveals an environmental reservoir.

BACKGROUND

In mid-2025, a sudden increase in urinary isolates of Myroides spp, was observed in high-dependency units (HDUs) of a tertiary-care hospital. This study aimed to determine whether the clustering represented sustained transmission or a pseudo-outbreak linked to a common source.

METHODS

A combined retrospective-prospective investigation was conducted in HDUs comprising 8 intensive care units and 1 palliative care unit (total capacity: 89 beds). Seventy-five unique patients with Myroides spp isolated from urine cultures between July 2024 and August 2025 were included. Prospective isolates underwent identification, susceptibility testing, biofilm assessment, rep-PCR, and selected 16S rRNA sequencing. Targeted environmental sampling was performed in units with case clustering.

RESULTS

A temporal peak occurred in June 2025 (n: 16). All prospectively analyzed isolates were identified as Myroides odoratimimus. Environmental sampling recovered the organism from urine collection containers. rep-PCR analysis of 33 isolates demonstrated a dominant molecular profile shared by 32 isolates, including 29 of 30 clinical isolates and all 3 environmental isolates. Most isolates showed strong biofilm production. After the introduction of single-use urine collection bags, no further isolates were detected.

CONCLUSIONS

These findings indicate a health care-associated pseudo-outbreak linked to an environmental source rather than sustained patient-to-patient transmission.