Misidentification ofBrucella melitensisasOchrobactrumspecies: potential pitfalls in the diagnosis of brucellosis

Abstract

We describe a case of brucellosis in a man in his 20s, who presented to the emergency department with a 1-month history of fevers, dry cough and knee pain. Blood cultures were positive after 55 hours andOchrobactrum daejeonensewas identified on matrix-assisted laser desorption/ionisation time of flight (MALDI-TOF) mass spectrometry.Ochrobactrumspp are Gram-negative organisms that are phylogenetically related toBrucellaspp but commercially available MALDI-TOF libraries cannot distinguish between the two genera. Further positive blood cultures forO. daejeonensecombined with characteristic growth patterns forBrucellaspp led to targeted questioning of the patient regarding potential exposure risks, which revealed a history of consumption of unpasteurised camel milk in the Middle East 3 months earlier. Treatment of brucellosis was initiated and subsequent whole genome sequencing identified the blood culture isolate asBrucella melitensisconfirming the diagnosis of brucellosis. This case highlights the challenges in the diagnosis of brucellosis in low-incidence settings.