Do Polymicrobial Intra-Abdominal Infections Have Worse Outcomes Than Monomicrobial Intra-Abdominal Infections?

Puja M. Shah, University of Virginia; Brandy Edwards, University of Virginia; Zachary Dietch; Robert Sawyer, University of Virginia HSC

Numerous studies have demonstrated microorganism interaction through signaling molecules, some of which are recognized by other bacterial species. This interspecies synergy can ultimately be detrimental to the human host in polymicrobial infections.

We hypothesize polymicrobial intra-abdominal infections (IAI) have worse outcomes than monomicrobial infections.

Data from STOP-IT, a prospective, multicenter randomized controlled trial was reviewed for all occurrences of IAI with culture results available. Patients in STOP-IT were randomized to receive four days of antibiotics versus antibiotics until clinical symptom resolution plus two additional days. Patients with polymicrobial and monomicrobial infections were compared by univariate analysis using Wilcoxon rank sum, Chi-square, and Fisher’s exact tests.

Culture results were available for 328 of 518 (63%) patients in the original study. Overall, duration of antibiotic therapy between polymicrobial (n=219) and monomicrobial IAI (n=109) were equal (p=0.97). Univariate analysis demonstrated similar demographics between the two populations. 35 patients with inflammatory bowel disease (11%), had a higher association with polymicrobial IAI (p=0.03). Polymicrobial infections were not associated with higher risk of surgical site infection, recurrent IAI, or death (Table 1).  

Contrary to our hypothesis, polymicrobial IAI are not associated with worse outcomes when compared to monomicrobial infections. These results suggest polymicrobial IAI can be treated similarly to monomicrobial IAI.