Microbiology and outcomes of hospitalization with intra-abdominal infections in the US: A retrospective cohort study

Author(s):
Marya Zilberberg; Brian Nathanson; Kenneth Lawrence; Kristen Ditch; Melanie Olesky; Andrew Shorr

Background:

Complicated intra-abdominal infections (cIAI) represent a major reason for hospital admission. Both source control and appropriate antibiotic therapy are central to successful management. Since anti-infectives are routinely given empirically, clinicians need to be aware of the current microbiology of this syndrome. It is also important to appreciate the burden of cIAI on the healthcare system.

Methods:

We performed a multicenter retrospective cohort study in the Premier database of approximately 180 hospitals, 2013-2017. Using an ICD-9/10 based algorithm including a requirement for a laparotomy/laparoscopy, we identified all adult patients hospitalized with cIAI and included those with a positive blood or abdominal culture. We examined the microbiology of these infections and the associated outcomes.

Results:

Among 4,453 patients with cIAI, 3,771 (84.7%) had a gram-negative (GN) and 1,782 (40.0%) had a gram-positive (GP) organism identified. Candida spp. were noted in 3.1% of cases. The majority of cases (n=2,941, 66.0%) were monomicrobial. Among patients with a polymicrobial infection, 1,118 (25.1%) had two organisms while 394 (8.8%) had three or more pathogens. Carbapenem resistance (CR) was present in 2.2% of all GN pathogens, and resistance to 3^rd generation cephalosporins (C3R) occurred in 7.6%. The most common GN pathogens were E. coli (2,624, 58.9%; 0.3% CR, 4.9% C3R) and K. pneumoniae (774, 17.4%; 1.6% CR, 2.5% C3R). Enterococcus spp. (1,072, 24.1%) were the most common GP. Hospital mortality was 7.6%, and 11.2% of survivors were readmitted within 30 days of discharge. The median [interquartile range] length of stay was 6 [3, 12] days and median total cost was $21,148 [$12,051, $43,637].

Conclusions:

Among patients hospitalized with a cIAI, 1/3 of the infections were polymicrobial, and the majority were GN. Among them, rates of CR and C3R were similar to those reported in other serious infections. cIAI hospitalizations are associated with substantial resource utilization and substantial morbidity and mortality. The low prevalence of polymicrobial infections may be due to under-recovery of anaerobic pathogens in clinical practice.