Treatment-emergent cefiderocol resistance in carbapenem-resistant Acinetobacter baumannii is associated with insertion sequence IS Aba36 in the siderophore receptor pirA

ABSTRACT We report the emergence of cefiderocol resistance in a bla OXA-72 carbapenem-resistant Acinetobacter baumannii isolate from a sacral decubitus ulcer. Cefiderocol was initially used; however, a newly approved sulbactam-durlobactam therapy with source control and flap coverage was successful in treating the infection. Laboratory investigation revealed cefiderocol resistance mediated by IS Aba36 insertion into the siderophore receptor pirA .