Does Isolation of Enterococcus Affect Outcomes in Intra-Abdominal Infections?

BACKGROUND: Enterococci are isolated frequently as pathogens in patients with intra-abdominal infections (IAIs) and may predict poor clinical outcomes. It remains controversial whether enterococci warrant an altered treatment approach with regard to antimicrobial treatment.

PATIENTS AND METHODS: The study population was derived from the Study to Optimize Peritoneal Infection Therapy (STOP-IT) trial database. Through post hoc analysis subjects were stratified into two groups based on isolation of Enterococcus. Fifty subjects of the cohort (n = 518) had Enterococcus isolated. Uni-variable and multi-variable analyses were conducted to determine whether isolation of Enterococcus constituted an independent predictor of the pre-defined STOP-IT composite outcome (surgical site infection, recurrent IAI, or death) and the individual components of the composite outcome.

RESULTS: From the cohort of 50 subjects, we identified 52 isolates of Enterococcus spp. with a predominance of Enterococcus faecalis (40%) followed by other Enterococcus spp. (37%) and Enterococcus faecium (17%). Baseline demographic characteristics were statistically similar between the two groups. Antibiotic utilization distribution remained balanced between the Enterococcus and no Enterococcus groups with the majority receiving piperacillin-tazobactam (62% and 54%, respectively). The groups had comparable infection characteristics including setting of acquisition (>50% community acquired) and origin of infection (predominantly colon or rectum). Individual and composite clinical outcomes were not different statistically between the Enterococcus and no Enterococcus groups: surgical site infection (10% vs. 7.5%; p = 0.53), recurrent IAI (20% vs. 14.1%; p = 0.26), death (2% vs. 1%; p = 0.40), and composite of all three (30% vs. 20.9%; p = 0.14], respectively. Multi-variable analysis revealed that isolation of Enterococcus did not predict independently the incidence of the composite outcome (odds ratio [OR] 1.53 [95% confidence interval {CI} = 0.78-3.01]; p = 0.22; c-statistic = 0.65; goodness of fit, p = 0.71).

CONCLUSIONS: Enterococcus was not a more common pathogen in health-care-associated IAIs and was not an independent risk factor for the composite outcome. The isolation of Enterococcus from IAIs may not warrant an alternative treatment approach but larger studies are needed to validate these findings.