Diagnostic value of metagenomic next-generation sequencing in deep neck space infections: a retrospective study of 32 patients.

Introduction: Deep neck space infections (DNSI) are rapidly progressive suppurative conditions in which early identification of causative pathogens is critical for clinical decision-making. This study evaluated the diagnostic performance and clinical utility of metagenomic next-generation sequencing (mNGS) in patients with DNSI. Methods: In this retrospective observational study, 32 patients with radiologically confirmed DNSI who underwent surgical drainage between October 2023 and August 2025 were included. Intraoperative purulent specimens were analyzed using both conventional bacterial culture and mNGS. A composite clinical reference standard integrating clinical presentation, imaging findings, surgical observations, inflammatory markers, and expert assessment was used to evaluate the clinical relevance of detected microorganisms. Results: mNGS detected microbial DNA in 84.4% of patients and demonstrated a broader pathogen detection spectrum and shorter reporting time than conventional culture, particularly for anaerobic and fastidious organisms. Frequently detected organisms included Prevotella spp. and Streptococcus constellatus. Interpretation of these findings required careful consideration of anatomical involvement, organism abundance, and prior antimicrobial exposure to distinguish clinically relevant pathogens from colonizing organisms or residual nonviable DNA. Discordant findings between culture and mNGS, including culture-positive/mNGS-negative and dual-negative cases, were observed and likely reflected differences in sampling adequacy, organism viability, sequencing depth, and methodological limitations. Antimicrobial therapy was adjusted in selected patients following mNGS reporting. Discussion: mNGS may serve as a valuable adjunct to conventional microbiological diagnostics by expanding pathogen detection in selected DNSI cases, particularly when fastidious or anaerobic organisms are involved. However, its results should be interpreted cautiously in the context of clinical and microbiological findings. Prospective controlled studies are needed to further define the clinical role of mNGS in the management of DNSI.