Analysis of Risk Factors and Resistance Genes for Carbapenem-Resistant Acinetobacter baumannii Bloodstream Infections: A Retrospective Study.

Objective

The prevalence of carbapenem-resistant Acinetobacter baumannii (CRAb) has been increasing globally. This study aimed to investigate the risk factors, resistance gene profiles, and molecular epidemiology of CRAb bloodstream infections (BSIs) among patients in Xi'an, China, to provide evidence for clinical prevention and targeted treatment.

Methods

We conducted a retrospective study of 139 patients with A. baumannii BSIs. Patients were categorized into a CRAb group (n = 84) and a carbapenem-susceptible A. baumannii (CSAb) group (n = 55). Independent risk factors were identified via multivariate logistic regression analysis. Carbapenemase resistance genes were detected using polymerase chain reaction (PCR), and CRAb isolates were molecularly typed by multilocus sequence typing (MLST).

Results

Multivariate logistic regression analysis identified the following as independent risk factors for CRAb BSIs: inappropriate empirical antimicrobial therapy (OR = 8.620; 95% CI: 2.078-35.751), deep venous catheterization (OR = 12.625; 95% CI: 2.263-70.429), prolonged hospitalization before the onset of BSIs (OR = 1.467; 95% CI: 1.123-1.915), and ICU admission (OR = 4.981; 95% CI: 1.898-13.065). Antimicrobial susceptibility testing showed that CRAb isolates were multidrug-resistant, exhibiting resistance rates exceeding 70% to most common clinical antibiotics, with the exception of tigecycline (5.95% resistance) and colistin (27.38% resistance). All 84 CRAb isolates carried both blaOXA-51-like and blaOXA-23-like genes, while other carbapenemase genes were not detected. MLST identified 7 sequence types (STs), with ST540 (45.24%, 38/84) being the dominant clone. eBURST analysis indicated that the major STs (ST195, ST208, etc.) belonged to the same clonal complex.

Conclusion

Inappropriate empirical antimicrobial therapy, deep venous catheterization, prolonged hospitalization before the onset of BSIs and ICU admission are independent risk factors for CRAb BSIs. The prevalent strains produce OXA-23-like carbapenemase, and molecular typing indicates that the ST540 clone and its related clonal complex are predominant, suggesting potential nosocomial clonal spread.