Clinical characteristics, antimicrobial resistance patterns, and outcomes of Corynebacterium bacteremia: a 15-year retrospective study.

BACKGROUND: Corynebacterium species are often regarded as blood culture contaminants, but they are increasingly recognized as true pathogens. However, their clinical significance, resistance patterns, and prognostic factors remain poorly defined. This study aimed to describe the clinical characteristics, antimicrobial resistance profiles, and factors associated with true bacteremia compared with isolates considered contaminants, as well as all-cause mortality. METHODS: We conducted a 15-year retrospective cohort study of adults with at least one Corynebacterium-positive blood culture at a tertiary-care university hospital in southern Thailand (2009-2024). Species identification was performed using MALDI-TOF MS from 2017 onward. True bacteremia was defined by clinical and microbiologic criteria. Multivariable logistic regression was used to identify independent predictors of true bacteremia, and Cox proportional hazards regression was applied to identify predictors of 30-day mortality. RESULTS: Among the 437 patients, 192 (44%) were classified as having true bacteremia. Independent predictors included hematologic malignancy (aOR 3.75; 95% CI: 1.40-10.73), central venous catheter use (aOR 2.39; 95% CI: 1.49-3.84), non-dialysis dependent chronic kidney disease (aOR 2.83; 95% CI: 1.11-7.66), and hypertension (aOR 1.92; 95% CI: 1.20-3.08). The 30-day all-cause mortality rate was significantly greater in true bacteremia patients (43.8% vs. 23.3%, p < 0.001). In the Cox proportional hazards model, hematologic malignancy (aHR 2.32, 95% CI 1.35-4.00) and central venous catheter use (aHR 2.34, 95% CI 1.46-3.74) were identified as independent predictors of 30-day mortality. C. striatum was the most common species (29.5%), highly resistant to penicillin (96.7%) and clindamycin (98.4%), but universally susceptible to vancomycin CONCLUSION: Nearly half of Corynebacterium-positive blood cultures represented true infections with high mortality. Vancomycin remains the most reliable empiric therapy. Species-level identification and susceptibility testing are essential for accurate diagnosis and management CLINICAL TRIAL: Not applicable.