Evolution and transmission of cefiderocol-resistant Acinetobacter baumannii during an outbreak in the burn intensive care unit.

We report 11 critically-ill burn patients treated with cefiderocol for carbapenem-resistant Acinetobacter baumannii infections. Clinical success was achieved in 36% and complicated by treatment-emergent resistance and inter-patient transmission of cefiderocol-resistant A. baumannii between patients. Resistant isolates harbored disrupted pirA and piuA genes that were not disrupted among susceptible isolates.