Spectrum of Anaerobic and Aerobic Pathogens in Intra-Abdominal Surgical Infections and Their Clinical Outcomes

Background: Intra-abdominal infections (IAIs) represent a significant cause of surgical morbidity and mortality, characterized by polymicrobial etiology involving complex interactions between aerobic and anaerobic pathogens. Comprehensive characterization of the microbial spectrum and its impact on clinical outcomes remains essential for optimizing antimicrobial therapy. Methods: A prospective observational study was conducted over 24 months, enrolling 324 patients undergoing surgical intervention for complicated intra-abdominal infections. Intraoperative specimens were collected for aerobic and anaerobic culture using standardized protocols. Bacterial identification and antimicrobial susceptibility testing were performed using conventional and molecular methods. Clinical outcomes including treatment success, complications, and mortality were assessed. Results: Polymicrobial infections were identified in 78.4% of cases, with a mean of 3.2 ± 1.4 isolates per patient. Aerobic organisms were recovered in 94.1% of cases, while anaerobes were isolated in 67.6%. Escherichia coli (58.3%) and Bacteroides fragilis (42.0%) were the predominant aerobic and anaerobic pathogens, respectively. Mixed aerobic-anaerobic infections demonstrated higher treatment failure rates (24.2% vs. 12.8%, p=0.018) and prolonged hospitalization (16.4 ± 8.2 vs. 11.8 ± 5.6 days, p