Killing two birds with one stone: emergence of colistin and cefiderocol resistance in a mucoid MDR Acinetobacter baumannii under colistin pressure

We recently described the first isolation of a mucoid strain of A. baumannii producing OXA-23 in a patient with cystic fibrosis (CF), a genetic disease characterized by bacterial chronic colonization of lung mucus. In the follow-up of the same patient, colonizing A. baumannii showed unexpected and undesirable adaptation to the antibiotic regimen to which the patient had been subjected. Here we describe the rapid emergence of concomitant resistance to COL and FDC in a hypermucoid (HM) A. baumannii strain, isolated from two sequential sputum samples of a cystic fibrosis (CF) patient.