Jingru Ji,1,* Wei Chen,2,* Peitao Jiang,3 Jie Zheng,4 Han Shen,4 Chang Liu,4 Yan Zhang,4 Xiwei Liao,1 Zhengnan Yang,3 Xiaoli Cao,3,4 Chao Wu1 

1Department of Infectious Disease, Nanjing Drum Tower Hospital, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, Nanjing, Jiangsu Province, People’s Republic of China; 2Clinical Research Center, the Second Hospital of Nanjing, Affiliated to Nanjing University of Chinese Medicine, Nanjing, Jiangsu Province, People’s Republic of China; 3Department of Clinical Laboratory, Yangzhou Yizheng Hospital, Yangzhou, Zhejiang Province, People’s Republic of China; 4Department of Clinical Laboratory, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, Jiangsu Province, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Xiaoli Cao, Department of Laboratory Medicine, Nanjing Drum Tower Hospital, Zhongshan Road 321, Gulou, Nanjing, Jiangsu Province, People’s Republic of China, Tel +00 86 25 83105360, Email cao-xiao-li@163.com Chao Wu, Department of Infectious diseases, Nanjing Gulou Hospital, Zhongshan Road 321, Gulou, Nanjing, Jiangsu Province, People’s Republic of China, Tel +00 86 25 83105360, Email wuchao1962@163.com

Background: Multidrug-resistant Acinetobacter baumannii (MDR-AB) is a major cause of bacterial bloodstream infections (BSIs), associated with high morbidity and mortality. The risk and prognostic factors for BSIs caused by clonally transmitted A. baumannii ST2, carrying armA, blaOXA-23 and blaOXA-66, remain unclear.
Methods: We retrospectively analyzed 97 hospitalized patients with A. baumannii BSI (January 2019–May 2022). Whole-genome sequencing and bioinformatic analysis characterized the strains. Clinical data were reviewed to identify risk factors for secondary BSIs, A. baumannii BSIs with mixed infections involving extra-bloodstream pathogens, and mortality predictors.
Results: High-risk clone sequence type (ST) 2 was identified in 87 isolates (89.7%), with 86 exhibiting clonal dissemination. Carbapenems and aminoglycosides resistance occurred in 78.4% of strains, linked to armA, blaOXA-23, and blaOXA-66. Patients’ median age was 56.6 years (range: 11– 93), with males comprising 62.9%. Elderly patients (> 65 years) accounted for 40.2%, 85.6% had hospital stays > 10 days, and 84.5% had ICU admissions. Adverse outcomes were observed in 55.7% of cases. ICU admission (OR = 5.144, 95% CI: 1.290– 20.511, P = 0.020) and open injury (OR = 5.998, 95% CI: 1.164– 30.892, P = 0.032) were specific risk factors significantly associated with BSIs, while the presence of three or more underlying diseases (OR = 6.419, 95% CI: 2.074– 19.866, P = 0.001) was significantly associated with increased mortality risk.
Conclusion: The majority of A. baumannii strains causing BSIs in this study belonged to multidrug-resistant ST2 lineage, harboring armA, blaOXA-23 and blaOXA-66. Risk factors for secondary and mixed infections included prolonged ICU stays, mechanical ventilation (≥ 7 days), and open injuries, while poor prognosis was linked to severe comorbidities and extended invasive ventilation. Targeted infection control strategies are critical to reducing mechanical ventilation duration and managing open injuries in high-risk patients.

Keywords: Acinetobacter baumannii, bloodstream infection, risk factors, molecular epidemiology, secondary infections, mixed infections