In vitro activity of cefiderocol and sulbactam-durlobactam against carbapenem-resistant Acinetobacter baumannii clinical isolates collected between 2019 and 2024.

BACKGROUND

The management of Acinetobacter baumannii infections has become increasingly challenging due to extensive antimicrobial resistance.

OBJECTIVES

This study evaluated the in vitro activity of cefiderocol and sulbactam-durlobactam and characterised OXA-type enzyme diversity in carbapenem-resistant A. baumannii isolates collected between March 2019 and December 2024.

METHODS

A total of 159 unique carbapenem-resistant isolates were tested for susceptibility to cefiderocol and sulbactam-durlobactam using two Food and Drug Administration-cleared minimum inhibitory concentration (MIC) determination methods: the ComASP Cefiderocol panel (Liofilchem, Italy) for cefiderocol and Etest strips (bioMérieux, USA) for sulbactam-durlobactam. Carbapenemase genes, including blaNDM, blaKPC, blaIMP, blaVIM, blaOXA-23, blaOXA-24/40, blaOXA-48, and blaOXA-58, were detected using real-time PCR.

RESULTS

Cefiderocol susceptibility was observed in 91.8% of isolates, with MIC50 and MIC90 values of 0.5 mg/L and 2 mg/L. Among blaOXA-23-positive isolates, MIC50 and MIC90 values were also 0.5 mg/L and 2 mg/L, while blaOXA-24/40-positive isolates showed MIC50 and MIC90 values of 0.25 mg/L and 1 mg/L, respectively. The sulbactam-durlobactam combination demonstrated potent in vitro activity against 97.5% of carbapenem-resistant Acinetobacter baumannii clinical isolates, with MIC50 and MIC90 values of 2 mg/L and 4 mg/L, respectively. Among the 159 carbapenem-resistant Acinetobacter baumannii isolates, 72.9% (n = 116) carried the blaOXA-23 gene, 10.7% (n = 17) harboured blaOXA-24/40, and 16.4% (n = 26) did not possess any of the carbapenemase genes included in the testing panel.

CONCLUSION

Cefiderocol and sulbactam-durlobactam exhibited strong in vitro activity against carbapenem-resistant A. baumannii isolates from a single University Hospital and may represent valuable treatment options for patients with limited therapeutic alternatives.