Examination of pathogens found in post-operative Intra-Abdominal Infections

Author(s):
William Wames; Robert Sawyer; Tjasa Hranjec

Background:

Post-operative intra-abdominal infection (IAI) is a commonly found pathology amongst patients in surgical critical care units. Consensus has been to treat susceptible patients with empiric antibiotics to cover the most common enteric bacteria as well as MRSA, yet the most common pathogens may have changed since original recommendations were made.

Hypothesis:

We hypothesized that previously uncommon pathogens may have increased in prevalence, contributing to ineffective empiric treatment.

Methods:

Data were compiled from 1997 thru 2023 from surgical critical care patients treated for culture positive post-operative intra-abdominal infection. Patient data was compiled including basic demographics, comorbidities, antibiotic treatment, and pathogens identified. Patients were analyzed based on year of infection: 1997-2003, 2004-2009, 2010-2015, and 2016-2023.

Results:

Among the 934 IAIs identified, the vast majority were secondary to residual contamination (n=516) with anastomotic leak (n=283), & new perforation (n=135) making up the remainder. The most common single pathogens found on culture were Candida species (n=403) with C albicans (n=231) being the single most common species across all identified. Enterococcus species (n=344) were the second most common genus. Common enteric pathogens Escherichia (n= 151), Klebsiella (n=85), and Bacteroides (n=67) spp. were found to make up far less of the bacterial burden than predicted by previous data. Little change in prevalence was noted over time (Figure).

Conclusions:

Intra-abdominal infections are commonly polymicrobial necessitating a broad empiric regimen, however, our data would suggest that current recommendations targeting mostly Gram negative and anaerobic pathogens may leave a vacuum for Candida and Enterococcus species. Future studies should focus on specific risk factors for specific organisms, allowing for more precise empiric therapy.