Microbiological spectrum and antimicrobial resistance patterns in pediatric acute appendicitis: implications for evidence-based empirical therapy

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Background Acute appendicitis is one of the most common surgical emergencies in children, and timely empirical antimicrobial therapy is particularly important in complicated cases. However, antibiotic selection is increasingly challenged by regional variability in pathogen distribution and antimicrobial resistance. This study aimed to characterize the microbiological spectrum and antimicrobial susceptibility profiles of purulent specimens from pediatric patients with acute appendicitis and to provide evidence for optimized empirical therapy. Methods In this prospective observational study, intraoperative purulent specimens were collected from 70 consecutive pediatric patients diagnosed with acute appendicitis between January 2024 and January 2025 at the Second Affiliated Hospital of Fuyang Normal University. All patients received a standardized preoperative antimicrobial regimen (cefuroxime 50 mg/kg plus metronidazole 7.5 mg/kg, administered intravenously within 30–60 min before surgical incision), which was documented for each case. Bacterial identification was performed using the VITEK® 2 Compact system. Antimicrobial susceptibility testing was conducted by broth microdilution in accordance with current Clinical and Laboratory Standards Institute (CLSI) guidelines. Extended-spectrum β -lactamase (ESBL) production was confirmed by the double-disk synergy test. Appendectomy specimens were independently evaluated by two board-certified pathologists according to predefined histopathological criteria. Results Pathogens were isolated from 62 of 70 specimens, yielding a culture-positive rate of 88.6%. Gram-negative bacteria predominated (98.3%), whereas only one Gram-positive isolate was identified. Escherichia coli was the most common pathogen (74.2%), followed by Pseudomonas aeruginosa (14.5%). Among E. coli isolates, 41.3% were ESBL producers. E. coli remained highly susceptible to amikacin and imipenem, but showed substantial resistance to co-trimoxazole and ceftriaxone. All P. aeruginosa isolates were susceptible to the tested antimicrobial agents. As a secondary descriptive outcome, acute appendicitis with peritonitis was the most frequent pathological subtype, accounting for 67.1% of the included cases. Conclusions Pediatric acute appendicitis in this cohort was dominated by Gram-negative pathogens, particularly ESBL-producing E. coli . The findings should be interpreted in the context of the study's aerobic culture methodology, which may have limited recovery of anaerobic organisms. These findings support the use of local resistance surveillance to guide severity-based empirical antibiotic selection, especially in complicated appendicitis.