Genomic and clinical insights into multidrug-resistant Corynebacterium striatum in a psychiatric hospital: development of an exploratory infection probability score

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Background: is increasingly recognized as a multidrug-resistant (MDR) opportunistic pathogen, yet its role in psychiatric hospitals remains poorly characterized. Differentiating colonization from true infection in this setting is clinically challenging. Methods: isolates were obtained from psychiatric inpatients with prolonged hospitalization. Antimicrobial susceptibility testing and whole-genome sequencing (WGS) were performed to characterize resistance determinants, virulence-associated genes, and phylogenetic relatedness. Ward distribution was mapped, and core-genome SNP-based phylogenetic analysis was performed. An exploratory Infection Probability Score (IPS) was developed using five routinely available variables, and its apparent performance in the derivation cohort was assessed against a predefined composite clinical reference standard using ROC analysis. Results: Most isolates displayed MDR phenotypes. Genomic analysis showed concurrent detection of multiple resistance genes together with several putative virulence-associated determinants, including iron-uptake- and adhesion-related genes. Core-genome SNP-based phylogenetic analysis demonstrated genetic diversity across isolates, with incomplete concordance between phylogenetic clustering and ward origin. In exploratory ROC analysis, the composite IPS showed higher apparent discriminatory performance than any single component marker (AUC = 0.795, 95% CI: 0.635-0.955). Conclusion: in long-term psychiatric inpatients. The IPS may offer a clinically interpretable framework for distinguishing infection from colonization in this underexplored setting, but its performance requires confirmation in larger, prospectively designed multicenter studies.