Linking Antimicrobial Agent Resistance Profiles to Clinical Outcomes in Pediatric Perforated Appendicitis

Background: Complicated appendicitis remains a leading cause of post-operative morbidity in children, but the relationship between specific microbial resistance profiles and clinical outcomes is poorly defined. Methods: We conducted a retrospective cohort study of pediatric patients (<18 y) who underwent appendectomy for complicated appendicitis at a tertiary children’s hospital (2019–2024). Demographic, operative, and outcome data were abstracted from the National Surgical Quality Improvement Program Pediatric database and electronic health records. Intra-operative cultures were analyzed for bacterial species, gram stain morphology, and antibiotic agent resistance. Hierarchical clustering of weighted resistance scores identified resistance-based microbial groupings. The primary outcome was post-operative organ–space infection (OSI), and secondary outcomes included length of stay (LOS) and 30-day re-admission. Results: Among 194 children (median age = 10.2 y; 56.2% male), 26 (13.4%) developed OSI. Culture analysis (n = 176 with samples) demonstrated that polymicrobial infections with ≥3 bacterial species isolated and the presence of Bacteroides fragilis increased the odds of OSI by 3.04× (95% confidence interval [CI] = 1.18–7.80, p = 0.010) and 2.40× (95% CI = 1.01–5.35; p = 0.021), respectively. Cluster analysis revealed three groups reflecting resistance burden and clinical phenotype. The Enterobacteriaceae group and a hard-to-treat cluster were associated with longer hospital stays (both p < 0.02), and the hard-to-treat cluster with increased 30-day re-admissions (5.6% vs. 1.5%; p = 0.040). Conclusions: Children with OSI exhibited distinct microbiologic features, including polymicrobial cultures and B. fragilis . Resistance-weighted clusters were linked to longer LOS and re-admission, highlighting that intra-operative cultures, traditionally considered low yield, may provide prognostic information with implications for post-operative management and antibiotic agent stewardship in pediatric complicated appendicitis.