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Association of early antibiotic therapy and in-hospital mortality in adult mild-to-moderate acute aspiration pneumonitis: a cohort study



Patients with aspiration pneumonitis often receive empiric antibiotic therapy despite it being due to a non-infectious, inflammatory response.


To study the benefits of early antibiotic therapy in patients with suspected aspiration pneumonitis in an acute care hospital.


Retrospective cohort study using electronic medical records from Teine Keijinkai Hospital.


Adults aged over 18 years admitted with a diagnosis of aspiration pneumonitis to the Department of General Internal Medicine or Emergency Department between January 1, 2008, and May 31, 2019. A diagnosis of aspiration pneumonitis was defined as a documented macro-aspiration event and a chest radiograph demonstrating new radiographic infiltrates.

Main measures

Patients were classified into the “early antibiotic treatment” group and the “no or late treatment” group depending on whether they received antibiotic therapy for respiratory bacterial pathogens within 8 h of arrival. The primary outcome was in-hospital all-cause mortality. Secondary outcomes included length of hospital stay, antibiotic-free days, duration of fever, readmission within one month, and incidence of complications.

Key results

Of the 146 patients enrolled, 52 (35.6%) did not receive early antibiotic therapy, while the remaining 94 (64.4%) did. There was no difference in in-hospital mortality rates between the groups after adjustment for potential confounding variables using Cox proportional hazards analysis (hazard ratio 2.78; 95% confidence interval, 0.57–13.50, p = 0.20). Patients in the no or late treatment group had more antibiotic-free days (p < 0.001) and a shorter length of hospital stay among survivors (p = 0.040) than did those in the early antibiotic treatment group. There were no statistically significant differences between the groups with respect to other secondary outcomes.


Early antibiotic therapy for acute aspiration pneumonitis was not associated with in-hospital mortality, but was associated with a longer hospital stay and prolonged use of antibiotics.

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This research received no specific grant from any funding agency.

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Corresponding author

Correspondence to Masaharu Aga.

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The study was approved by the Institutional Review Board of Teine Keijinkai Hospital.

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Aga, M., Naganuma, T., Ohashi, Y. et al. Association of early antibiotic therapy and in-hospital mortality in adult mild-to-moderate acute aspiration pneumonitis: a cohort study. Intern Emerg Med 16, 1841–1848 (2021).

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  • Aspiration pneumonitis
  • Aspiration pneumonia
  • Pneumonitis
  • Antibiotic therapy
  • Antimicrobial stewardship