Appendicular Versus Non-Appendicular Community-Acquired Intra-Abdominal Infections: A Post-Hoc Analysis of the PERICOM Multicenter Study

Background: Community-acquired intra-abdominal infections (CA-IAIs) exhibit significant clinical heterogeneity. However, most studies focusing on CA-IAIs do not stratify comparisons by infection site. Methods: This post hoc analysis of the prospective multicenter PERICOM cohort (13 French university hospitals, April 2018 to February 2019) included adult patients with CA-IAIs requiring surgical management. We compared clinical characteristics, microbiology, and outcomes between appendicular and non-appendicular sites. Secondary analyses assessed the impact of Enterococcus spp., Pseudomonas aeruginosa, or fungal documentation, and the theoretical coverage of empirical antibiotic regimens. Results: Of the 205 patients, 86 (42%) had appendicular and 119 (58%) had non-appendicular CA-IAIs. Appendicular CA-IAIs involved younger patients with fewer comorbidities and were followed by fewer major postoperative complications (Clavien-Dindo score ≥ 3: 10% versus 43%, p < 0.001) and no deaths (0% versus 12%, p < 0.001). Among 118 culture-positive patients, appendicular CA-IAIs showed higher rates of non-fermenting Gram-negative bacilli (25% versus 10%, p = 0.046) and anaerobes (53% versus 28%, p = 0.008) and were more often polymicrobial (76% versus 55%, p = 0.020). Conversely, Staphylococcus spp. (0% versus 9%, p = 0.036) and fungal co-infection (0% versus 12%, p = 0.010) were confined to non-appendicular CA-IAIs. Furthermore, Enterococcus spp. documentation (24/118, 20%) identified patients with greater admission severity and higher 28-day mortality (33% versus 2%, p < 0.001). Amoxicillin-clavulanic acid plus gentamicin covered the isolates of 92% of patients versus 61% for third-generation cephalosporin plus metronidazole (p < 0.001), a difference identical in both appendicular and non-appendicular sites. Conclusions: Appendicular and non-appendicular CA-IAIs appear to be distinct entities, supporting stratified management. Future guidelines should consider site-specific strategies, therapeutic individualization, and the integration of CA-IAI ecology.