Biological sex influences severity and outcomes in Acinetobacter baumannii pneumonia

• DOI: 10.1128/spectrum.03199-24
• Publication Date: 2025-04-16T13:01:21Z
• Authors: Matthew S. Linz; Louis Collins; Emily Keenan; Ruchi Biswas; Dov Levine; Arun Mattappallil; Diana Finkel; Dane Parker

ABSTRACT

Biological sex is known to affect the incidence and outcomes of infection, varying significantly by pathogen. The bacterial pathogen Acinetobacter baumannii is recognized as a serious global healthcare threat worldwide, yet understanding of how biological sex impacts its infection course is limited. We previously documented in a murine model of acute pneumonia that female mice were more susceptible to infection, but there are no published studies looking at outcomes in humans according to biological sex. We conducted a retrospective cohort study of 220 adult patients with a positive A. baumannii culture and clinical evidence of pneumonia. Contrary to the animal data, we observed male patients to have a longer overall (32 vs 24 days, P < 0.05) and intensive care unit (ICU) length of stay (LOS) (23 vs 17 days, P < 0.001) compared to females. The primary diagnosis at admission was only a factor when it was respiratory in nature. Younger male patients had higher Pneumonia Severity Index score on admission compared to younger females. Older males required more interventions than younger males. We also observed that mortality rates were increased for patients with chronic obstructive pulmonary disease ( P = 0.024) and renal disease ( P < 0.001), while alcohol use or smoking within 30 days prior to admission or recent surgery all negatively impacted LOS. This study highlights the importance of sex-and-gender-based studies, identifying worse outcomes in men, the elderly, and patients with certain underlying conditions and guiding efforts to improve management of patients with A. baumannii pneumonia.

IMPORTANCE

Biological sex has been shown to influence the incidence and outcomes of infection. We had previously documented that in a mouse model of infection, the pathogen Acinetobacter baumannii caused more serious pulmonary disease in female animals. In this study, we aimed to determine if this was evident in human pneumonia data. We found that, opposite to the mice data, human males had extended hospital stays due to A. baumannii pneumonia. We also identified a number of risk factors that can impact mortality and duration of hospital stay. This information could be used to guide efforts to improve management of patients with A. baumannii pneumonia.