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Volume 52, Number 2, April 2019

Clonal relationship and the association of the ST218 strain harboring blaOXA-72 gene to mortality in carbapenem-resistant Acinetobacter baumannii bacteremia 


Chang-Pan Liu, Hsi-Peng Lu, Tainyi Luor


 

Background and purpose: 

In 2017, the World Health Organization categorized carbapenem-resistant Acinetobacter baumannii (CRAB) as a priority 1, critical antibiotic-resistant bacteria. This study analyzed the clinical outcomes and investigated the molecular epidemiology of CRAB bacteremia in a medical center in Northern Taiwan. 



 

Methods:

We collected 62 blood isolates from patients with CRAB bacteremia from January 2014 to December 2015 at MacKay Memorial Hospital and determined the clonal relationship using the PCR-based technique for molecular epidemiology. Medical charts were reviewed for clinical outcomes.Fifty-six isolates harbored the blaOXA-51-like and blaOXA-23-like carbapenemase genes, 4 isolates harbor the blaOXA-51-like and blaOXA-24-like carbapenemase genes and 2 isolates harbored only the blaOXA-51-like gene. After sequencing, all four isolates of blaOXA-24-like carbapenemase gene were confirmed to be isolates of blaOXA-72 carbapenemase genes. In multivariate analysis in the 60 patients, the independent mortality risk factors of CRAB bacteremia included ≥65 years (elderly) (Odds ratio, 4.04, 95% CI, 1.10–14.83, p = 0.035), chronic kidney disease (4.36, 1.14–16.72, p = 0.032). Isolates harboring the blaOXA-72 gene had the same sequence type (ST218) and PFGE pulsotype raising the possibility of intra-hospital transmission, and all infected patients died. 



 

Results:

Fifty-six isolates harbored the blaOXA-51-like and blaOXA-23-like carbapenemase genes, 4 isolates harbor the blaOXA-51-like and blaOXA-24-like carbapenemase genes and 2 isolates harbored only the blaOXA-51-like gene. After sequencing, all four isolates of blaOXA-24-like carbapenemase gene were confirmed to be isolates of blaOXA-72 carbapenemase genes. In multivariate analysis in the 60 patients, the independent mortality risk factors of CRAB bacteremia included ≥65 years (elderly) (Odds ratio, 4.04, 95% CI, 1.10–14.83, p = 0.035), chronic kidney disease (4.36, 1.14–16.72, p = 0.032). Isolates harboring the blaOXA-72 gene had the same sequence type (ST218) and PFGE pulsotype raising the possibility of intra-hospital transmission, and all infected patients died. 



 

Conclusion:

This study showed the clonal relationship of isolates harboring the carbapenemase gene in CRAB bacteremia. Patients with the ST218 strain harboring blaOXA-72 gene had high mortality. This warrants further research to determine the mechanism of virulence and risk factors in order to reduce mortality.This study showed the clonal relationship of isolates harboring the carbapenemase gene in CRAB bacteremia. Patients with the ST218 strain harboring blaOXA-72 gene had high mortality. This warrants further research to determine the mechanism of virulence and risk factors in order to reduce mortality. 



 

Key words:

Acinetobacter baumannii bacteremia; blaOXA-72; Clonal relationship ST218