Is the Isolation of Pseudomonas aeruginosa Associated with Outcomes from Intra-Abdominal Infection? No,But the Receipt of an Empiric Anti-Pseudomonal Agent Is

Abstract

Background:

Pseudomonas aeruginosa is isolated at variable rates from intra-abdominal infections (IAI). Not all recommended empiric regimens for IAI include anti-Pseudomonas aeruginosa activity, for example, ceftriaxone and metronidazole. We hypothesized that within an adult population, Pseudomonas aeruginosa is a relatively rare isolate and has no association with mortality, and thus, empiric therapy with anti-Pseudomonas aeruginosa activity is not warranted.

Patients and Methods:

All IAI with positive cultures treated between 1997 and 2017 at a single institution were analyzed. This data set was divided into two cohorts, namely, those with cultures positive for Pseudomonas aeruginosa and those without. Demographics and in-hospital mortality were compared by Student t-test and χ² analysis. Predictors of isolation of Pseudomonas aeruginosa and in-hospital mortality were done by logistic regression (LR) analysis.

Results:

In total, 2,420 IAIs were identified, 104 (4.3%) with Pseudomonas aeruginosa and 2,316 (95.7%) without. Major demographic differences between patients with Pseudomonas aeruginosa and those without included a higher rate of health-care–associated infections (87/104, 83.7% vs. 621/2316, 26.8%; p = 0.02), a higher rate of intensive care unit (ICU)-acquired infections (23/104, 22.1% vs. 329/2316, 14.2%; p = 0.04) and a higher Acute Physiology and Chronic Health Evaluation (APACHE) II score (17.7 ± 0.8 vs. 14.5 ± 0.2; p < 0.0001). There was an increased rate of Pseudomonas aeruginosa isolation with increasing APACHE II score. Independent predictors of isolation of Pseudomonas aeruginosa by LR included APACHE II score and days of hospitalization prior to diagnosis. Crude in-hospital mortality was similar between groups: Pseudomonas aeruginosa 14/104 (13.5%) and 276/2316 (11.9%), p = 0.79. After controlling for age, gender, APACHE II, prior transfusion, immunosuppression status, solid organ transplant status, healthcare-association, and days of hospitalization prior to diagnosis, the isolation of Pseudomonas aeruginosa was not associated with mortality.

Conclusion:

Pseudomonas aeruginosa is infrequently isolated and overall not associated with mortality. Nonetheless, there may be a population that merits empiric anti-Pseudomonas aeruginosa therapy: those with APACHE II ≥20 or a significant length of hospitalization prior to diagnosis.