Peritonitis is a frequent cause of sepsis in the intensive care unit (ICU) and is characterized by substantial microbiological variability, including multidrug-resistant organisms (MDROs).

We conducted a retrospective, multicenter cohort study including ICU patients diagnosed with intra-abdominal infection across 4 hospitals 2020–2022). The primary objective was to describe clinico-biological features, and microbiological characteristics according to the setting of the peritonitis (Community peritonitis (CP), early nosocomial peritonitis (ENP), or late nosocomial peritonitis (LNP)). Additionally, we analyzed 90-day survival using Kaplan–Meier curves and multivariable Cox regression.

Among the 392 patients included in the study period, 195 experienced a CP, 88 an ENP, and 109 an LNP. Extended-spectrum beta-lactamase-producing bacteria were identified in 24 patients (6.1%), and carbapenem-resistant bacteria in 5 patients (1.3%). MDRO rates differed significantly: carbapenem-resistant bacteria were more frequent in LNP patients (3.7% vs. 0.0% in CP and 0.5% in ENP; p  = 0.03), and cephalosporinase-producing bacteria were more common in nosocomial settings (40.4% in LNP vs. 19.0% in CP; p   <  0.001). Ninety-day mortality was 34.7% overall and did not differ across settings ( p  = 0.345). Age and SAPS II were independently associated with mortality. Finally, appropriate empirical antimicrobial therapy was not associated with improved 90-day survival ( p  = 0.128).

Through this large cohort study of ICU patients with peritonitis, we observed a low prevalence of MDRO. Our findings challenge the relevance of broad-spectrum empirical therapy in low-MDRO regions and underscore the need for tailored antimicrobial stewardship strategies.