Bacterial Etiology and Antimicrobial Susceptibility Patterns in Pediatric Intra-Abdominal Infections—Implications for Empirical Treatment and Antimicrobial Stewardship

Objectives: Intra-abdominal infections (IAIs) requiring surgical intervention represent a significant cause of morbidity in pediatric patients, often leading to prolonged hospitalization and increased antimicrobial exposure. This study aimed to characterize the distribution of pathogenic bacteria, antimicrobial resistance patterns, and clinical associations in pediatric intra-abdominal infections complicated by surgical site involvement. Methods: A retrospective observational study was conducted on children aged 0–16 years, who underwent surgery for intra-abdominal infections with microbiological confirmation. Peritoneal fluid, pus, and other intraoperative or postoperative specimens were analyzed using standard microbiological techniques. Infections were classified as monomicrobial or polymicrobial, and antimicrobial susceptibility was assessed phenotypically. Associations between bacterial pathogens, patient age, underlying diagnosis, surgical procedures, and antibiotic susceptibility patterns were analyzed. Results: 177 pediatric patients were included. Appendicitis was the most common diagnosis (53.53%), followed by intra-abdominal abscesses (32.94%). Gram-negative (GN) bacteria predominated (44.07%), with Escherichia coli being the most frequently isolated pathogen (83.33%). Double and triple GN and GP associations were identified in approximately 25% of cases, particularly in abscesses, complicated appendicitis, and surgical site infections. Our findings revealed that piperacillin–tazobactam and carbapenems were expected to be effective against almost all GN pathogens identified in surgical specimens of pediatric patients. Pathogen distribution and antimicrobial susceptibility varied significantly according to age group and clinical diagnosis. Conclusions: In pediatric patients, intra-abdominal infections requiring surgical management were mainly caused by Gram-negative bacteria and polymicrobial associations. Effective treatment relies on prompt surgical source control and empiric broad-spectrum antimicrobial therapy, followed by culture-guided de-escalation to support antimicrobial stewardship.