Metagenomic landscape of peripancreatic necrotic pus in acute pancreatitis: pathogen ecology, resistance gene profiles, and disease-associated microbial patterns.

OBJECTIVE: To characterize the metagenomic landscape of intra-abdominal pus from surgical ICU patients using metagenomic next-generation sequencing (mNGS), compare pathogen ecology and resistance gene profiles between acute pancreatitis (AP)-associated and non-pancreatitis abdominal infection, and examine the association between pancreatitis-associated microbial features and persistent organ failure status. METHODS: A total of 115 patients undergoing abdominal paracentesis and drainage in a surgical ICU were stratified into three groups: the POF group (AP with persistent organ failure, n = 35), the Non-POF group (AP without persistent organ failure, n = 49), and the Non-AP group (non-pancreatitis intra-abdominal infection, n = 31). Pus samples were analyzed by mNGS to characterize pathogen profiles, antimicrobial resistance gene (ARG) carriage, and microbial community structure. RESULTS: Compared with Non-AP infections, both AP groups showed a convergent microbial profile dominated by ICU-associated pathogens, including Enterococcus faecium, Klebsiella pneumoniae, Acinetobacter baumannii complex, and Pseudomonas aeruginosa, with broad ARG detection profiles. ARG positivity was higher in AP patients than Non-AP controls (69.0% vs. 45.2%; P = 0.029), with frequent detection of Beta-lactam resistance genes, including carbapenemase-related genes. At sampling, alpha and beta diversity did not differ between POF and Non-POF groups, whereas both AP groups were clearly separated from Non-AP infections (P < 0.01). Among species enriched in Non-AP pus, Enterococcus faecalis remained inversely associated with AP status after adjustment for comorbidity burden, disease severity, antibiotic exposure, and ICU exposure (all P ≤ 0.006). The family-level random forest model achieved exploratory discriminatory performance for AP identification (AUC = 0.843). CONCLUSION: AP-associated peripancreatic pus harbored a distinct microbial ecological profile characterized by reduced community diversity, predominance of ICU-associated pathogens, and broad ARG detection profiles. This pattern was associated with AP status but not with POF at sampling. These findings may complement antimicrobial risk assessment and empirical treatment decisions when interpreted alongside culture-based susceptibility testing and clinical factors, but require validation in prospective multicenter studies.