25th February 2025

A 35-year-old man presents to A&E with an acutely painful wrist.

A 35-year-old man presents to A&E with an acutely painful wrist. On examination, he is tachycardic and febrile, with a hot swollen joint that he is unable to move. You also note track marks up the veins, and he admits to intravenous drug use.

FBC shows:

Hb 110 (120-180)

MCV 97 (90-97)

Plts 470 (150-450)

WCC 20.2 (4-11)

Neutrophils 14 (1.5-8)

Lymphocytes 4.7 (1.1-4)

Monocytes 1 (0.2-1.1)

Eosinophils 0.3 (0.1-0.4)

Basophils 0.2 (0-0.3)

An urgent aspiration is performed, and the culture comes back showing Gram-negative rods. What is the likely causative organism?

Select the SINGLE most appropriate option from the list below. Select ONE option only.