The association between empiric antimicrobial therapy and the risk of clinical failure in critically ill patients with aspiration pneumonia.

Abstract

Aspiration pneumonia is a clinically important infectious process that can result in increased morbidity and mortality. Empiric antimicrobial therapy with activity against anaerobes has been a standard practice based on previous studies, which isolated anaerobes from respiratory cultures. Recent studies have failed to identify anaerobes as causative pathogens, however, these studies did not assess patient outcomes based on the presence or absence of anaerobic coverage. This retrospective cohort study evaluated patients at least 18 years of age requiring mechanical ventilation diagnosed with aspiration pneumonia between 1 October 2020 and 31 July 2021. The primary outcome was the incidence of clinical failure. Secondary outcomes included the time to clinical failure, the incidence of Clostridioides difficile infections and development of multidrug-resistant infections, as well as time on mechanical ventilation and intensive care unit length of stay. A total of 141 patients were included with 83 patients initially receiving anaerobic coverage and 58 patients treated without anaerobic coverage. There was no difference in the incidence of clinical failure between cohorts (18.1% vs. 22.4%; p= 0.41). There was a statistically significant difference in anaerobic escalations with more escalations in the cohort without anaerobic coverage (0% vs. 20.7%; p< 0.0001). Patients initially treated with drugs with anaerobic activity had a higher incidence of multidrug resistant infections on current admission (7.2% vs. 0%; p= 0.04) and a longer length of intensive care unit stay. In critically ill adults with aspiration pneumonia, our study found no difference in clinical failure based on the presence or absence of empiric anaerobic coverage adding to evolving literature suggesting that anaerobic coverage is not routinely warranted in this patient population. Interpretation of the results needs to consider, however, that the retrospective design led to the inclusion of sicker patients in the anaerobic cohort. The frequency of empiric anaerobic coverage demonstrates the need for a prospective randomized control trial to confirm these findings.