Metagenomic Sequencing for Diagnosing Listeria-Induced Rhombencephalitis in Patient and Contaminated Cheese Samples: A Case Report.

Among the various causes of rhomboencephalitis, Listeria monocytogenes infection is the most common. However, conventional microbiological methods often yield negative results, making diagnosis challenging and leading to extensive, often inconclusive, diagnostics. Advanced molecular techniques like metagenomic next-generation sequencing (mNGS) offer a powerful and efficient approach to pathogen identification. We present a case of life-threatening rhomboencephalitis in a 32-year-old immunocompetent patient where extensive microbiological, immunological, and biochemical tests were inconclusive. Given the patient's consumption of unpasteurized homemade cheese, neurolisteriosis was suspected, and mNGS was employed on clinical samples (CSF, serum, urine) and the food source to identify the pathogen. mNGS detected L. monocytogenes in both patient samples and the cheese. Mapping reads were distributed across the genome, with 18.9% coverage in clinical samples and 11.8% in the cheese sample. Additionally, the Listeriolysin (hlyA) gene was detected with 22.3% coverage in clinical samples and 12.3% in the food source, confirming neurolisteriosis. The patient fully recovered following antibiotic treatment. This case underscores the importance of mNGS in diagnosing CNS infections when conventional methods yield negative results, and supports its inclusion in diagnostic protocols for suspected neurolisteriosis, particularly when traditional methods prove inadequate.