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Bacterial population and antibiotic resistance in peritoneal cultures of complicated pediatric appendicitis: retrospective study from a tertiary center
António Moreira, Ana Magalhães, Diogo Cardoso, Elizabete Vieira
Hospital de Santa Maria, Lisbon
Dominant microbiota and antibiotic resistance patterns in pediatric complicated appendicitis vary by region, reinforcing the need for local surveillance to optimize empirical therapy. We performed a study to (1) characterize the dominant microbiota from patients with complicated acute appendicitis, (2) analyze antibiotic resistance patterns, and (3) evaluate the association between bacterial resistance, post-operative complications, and hospital stay.
We conducted a retrospective study of pediatric patients with complicated appendicitis undergoing appendectomy between 2017 and 2023 in a tertiary center. All patients received standard empirical antibiotic therapy (ampicillin, gentamicin and metronidazole), and peritoneal fluid samples were collected intraoperatively for analysis. Of 338 cases, 220 had positive cultures. Descriptive analysis was performed on the bacterial population and antibiotic sensitivity. The relationship between antibiotic resistance, incidence of post-operative complications and hospital stay was also assessed.
The most frequently isolated bacteria were Escherichia coli (n=174) and Bacteroid genus (n=114). Most E. coli strains were sensitive to amoxicillin/clavulanate (77.1%) and trimethoprim/sulfamethoxazole (69.2%), but only 41.4% to ampicillin. Five extended-spectrum β-lactamase-producing E. coli strains were identified. Bacteroid strains were highly sensitive to amoxicillin/clavulanate (100%) and metronidazole (99%). Pseudomonas aeruginosa was the third most frequent agent (n=47), fully sensitive to piperacillin/tazobactam, ciprofloxacin, and gentamicin.
No significant association was found between resistance to empirical antibiotic regimen and post-operative complications (p=0.706) or prolonged hospital stay (p=0.560). Similarly, no association was found between ampicillin resistance and post-operative complications (p=0.851).
In our center, E. coli, Bacteroid genus, and P. aeruginosa were the most common pathogens. The increasing resistance of E. coli to ampicillin highlights the need to revise the empirical antibiotic regimen. However, no correlation was found between bacterial resistance and adverse outcomes, possibly due to the prompt adjustment of antibiotic therapy based on culture results.