Metagenomic analysis reveals severity-dependent microbial succession and correlation with host inflammatory response in oral and maxillofacial space infections.

Background: Oral and maxillofacial space infections (OMSI) vary widely in clinical severity, yet the relationships between microbial community patterns in the abscess niche and host inflammatory responses remain incompletely characterized. Methods: We conducted a retrospective, cross-sectional, severity-stratified study of 197 patients diagnosed with OMSI between January 2020 and November 2023. Patients were stratified into mild (n=90), moderate (n=41), and severe (n=66) groups based on established clinical criteria. We performed mNGS on abscess pus samples to characterize the microbial community composition and assessed associations between these features and systemic inflammatory markers. Results: Although α-diversity did not differ significantly among severity groups, β-diversity analysis revealed distinct microbial communities. Pairwise analyses indicated a threshold-like community shift, characterized by a significant divergence between mild and severe infections, while the moderate group exhibited an intermediate composition that overlapped with both. Severe infections were characterized by an enrichment of Conclusion: This study characterizes associations between abscess-site microbial communities and host inflammatory profiles across OMSI severity strata. Given the cross-sectional design and the lack of an external validation cohort, the present findings should be interpreted as exploratory and non-causal. Future multicenter prospective studies including independent validation cohorts are warranted to test reproducibility and to evaluate whether any candidate features possess generalizable predictive value.