Cefiderocol-associated brown chromaturia.

Cefiderocol is a novel siderophore cephalosporin antibiotic. In the present case report, a woman in her 70s presented with a 1-week history of altered mental status and progressive purulent discharge from a non-healing diabetic foot ulcer on her right heel. MRI of the right foot revealed chronic osteomyelitis of the calcaneum. Surgical debridement was performed, and the tissue cultures grew extensively drug resistant (XDR) Pseudomonas aeruginosa, XDR Acinetobacter baumannii and Enterococcus faecalis The patient received ampicillin-sulbactam and cefiderocol. The antibiotic treatment course was complicated by brown urine discolouration. Investigations were unrevealing for haemoglobinuria, myoglobinuria and bilirubinuria. A side effect from cefiderocol was suspected and subsequently discontinued. Her urine colour returned to its normal colour within 3 days of discontinuation of cefiderocol.