Aerobic and Facultative Bacterial Spectrum and Antimicrobial Susceptibility Patterns in Pediatric Acute Appendicitis: A Prospective Local Surveillance Study.

BACKGROUND: Acute appendicitis is one of the most common surgical emergencies in children. In complicated appendicitis, timely empirical antimicrobial treatment is important, but antimicrobial selection is increasingly affected by regional variation in pathogen distribution and resistance. This study characterized the aerobic and facultative bacterial isolates recovered from intraoperative purulent specimens obtained from pediatric patients with acute appendicitis and described their antimicrobial susceptibility patterns.

METHODS: This prospective observational study enrolled 70 consecutive pediatric patients who underwent appendectomy for acute appendicitis at the Second Affiliated Hospital of Fuyang Normal University between January 2024 and January 2025. Intraoperative purulent material was collected using sterile swabs and processed by routine aerobic culture methods. No dedicated anaerobic culture or culture-independent molecular analysis was performed. Bacterial identification was conducted using the VITEK 2 Compact system. Antimicrobial susceptibility testing was performed using broth microdilution and interpreted according to the applicable Clinical and Laboratory Standards Institute criteria. Extended-spectrum β-lactamase production among Escherichia coli isolates was confirmed using the double-disk synergy test. Appendicitis was operationally categorized as uncomplicated or complicated according to operative and pathological findings.

RESULTS: Aerobic or facultative bacterial growth was detected in 62 of 70 specimens, corresponding to a culture-positive rate of 88.6% (95% confidence interval, approximately 78.2%-94.0%). A total of 62 isolates were recovered from the 62 culture-positive specimens, and no polymicrobial aerobic or facultative growth was recorded using the applied culture strategy. Gram-negative organisms accounted for 61 of 62 isolates (98.4%). E. coli was the predominant isolate (46/62, 74.2%), followed by Pseudomonas aeruginosa (9/62, 14.5%). Nineteen of the 46 E. coli isolates (41.3%) were ESBL producers. E. coli retained high in vitro susceptibility to amikacin and imipenem but showed substantial resistance to ceftriaxone and trimethoprim-sulfamethoxazole. All nine P. aeruginosa isolates were susceptible to the antimicrobial agents tested. Based on the revised clinical classification, nine patients had uncomplicated appendicitis and 61 had complicated appendicitis.

CONCLUSIONS: The organisms recovered with the present culture strategy were predominantly aerobic or facultative gram-negative bacteria, especially E. coli, and ESBL production was frequent among E. coli isolates. These findings provide local surveillance information that may support antimicrobial stewardship and the reassessment of empirical coverage in pediatric appendicitis. However, because anaerobic culture, treatment comparisons, and comprehensive outcome analyses were not performed, the study does not characterize the complete appendiceal microbiota or establish the superiority of a specific empirical antimicrobial regimen.