A 12-year retrospective single-center comparison of pneumonia- and non-pneumonia-related Acinetobacter baumannii complex bacteremia

Abstract Background Acinetobacter baumannii complex (ABC) is a group of increasingly prevalent opportunistic pathogens that cause a variety of life-threatening nosocomial infections, especially in the intensive care unit (ICU). It is unclear whether ABC bacteremia differs with infection site. This study assessed the differences between pneumonia- and non-pneumonia-related ABC bacteremia and possible independent risk factors for 30-day mortality. Methods The clinical data of 188 patients diagnosed with ABC bacteremia in our 29-bed ICU between January 2009 and December 2020 were collected. Of these, 44 cases (23.4%) were defined as pneumonia-related ABC bacteremia and 144 (76.6%) as non-pneumonia-related ABC bacteremia. Results Significant changes in the incidence of ABC bacteremia and antibiotic resistance were observed over the 12-year study, with an overall 30-day mortality rate of 61.7%. Compared with non-pneumonia-related ABC bacteremia, pneumonia-related ABC bacteremia was associated with a higher rate of hypertension, less prior tigecycline use, more carbapenem-resistant (CR) strains, and had a higher 30-day mortality rate. Univariate analysis showed that hematological malignancy, previous corticosteroid use, prior exposure to quinolone and anti-fungal agents, CR strains, monomicrobial bacteremia, respiratory tract bacteremia origin, lower albumin and higher lactate levels at the time of bacteremia, immunosuppression, septic shock, and severity of illness based on the Pitt bacteremia score, Acute Physiology and Chronic Health Evaluation II (APACHE II), and Sequential Organ Failure Assessment (SOFA) scores at the time of bacteremia were associated with poor outcomes. In multivariate analysis, immunosuppression, and higher APACHE II and SOFA scores, were risk factors for 30-day mortality. Moreover, the risk of death was 1.919 times higher in the pneumonia-related group. Conclusions Our study described the clinical characteristics and independent predictors of 30-day mortality in patients with pneumonia- and non-pneumonia-related ABC bacteremia. Although pneumonia-related ABC bacteremia had worse outcomes, it was not an independent risk factor for death statistically. Detection of immune status and maintenance of organ function may be effective therapeutic strategies to improve patient outcomes.