Brucellosis with Spondylodiscitis
A 44-year-old Saudi farmer has 3 months of undulating fever, night sweats, and low back pain radiating to both legs. He drinks unpasteurised camel milk. There is bony tenderness over the lumbar spine, and MRI shows L4 to L5 spondylodiscitis. Blood cultures grow slow-growing gram-negative coccobacilli. Which of the following is the most likely diagnosis?
- A.Spinal tuberculosis
- B.Visceral leishmaniasis
- C.BrucellosisCorrect
- D.Schistosomiasis
Explanation
Brucellosis is endemic across the Arabian Peninsula and is acquired from unpasteurised milk or direct contact with goats, sheep, and camels, making occupational and dietary history decisive. The classic syndrome is undulating fever with night sweats, malaise, arthralgia, and, in up to a third of cases, osteoarticular involvement such as sacroiliitis, peripheral arthritis, or spondylodiscitis, which explains the back pain radiating to the legs and the vertebral tenderness. The microbiological clue is definitive: Brucella species are small, slow-growing, facultative intracellular gram-negative coccobacilli, and laboratories should be warned so cultures are held longer and handled safely. Serology by the standard agglutination test supports the diagnosis when cultures are negative, and MRI defines the extent of spinal disease. Treatment requires combination therapy, typically doxycycline with rifampicin for at least 6 weeks, extended to 3 months or longer with an added aminoglycoside for spondylitis, endocarditis, or neurobrucellosis, because monotherapy leads to relapse. Spinal tuberculosis produces a similar chronic back pain syndrome but yields acid-fast bacilli with caseating granulomas, not gram-negative coccobacilli on blood culture. Visceral leishmaniasis causes fever with massive splenomegaly and pancytopenia and is diagnosed by amastigotes on marrow or splenic aspirate. Schistosomiasis is a helminth infection diagnosed by eggs in urine or stool and does not grow on blood culture.
Why each option
- A.
- Spinal tuberculosis mimics the clinical picture but is diagnosed by acid-fast bacilli and caseating granulomas, and mycobacteria are not gram-negative coccobacilli.
- B.
- Visceral leishmaniasis presents with fever, marked splenomegaly, and pancytopenia, and is diagnosed by tissue amastigotes rather than blood culture.
- C.
- Correct. Undulating fever with vertebral involvement, unpasteurised milk exposure, and slow-growing gram-negative coccobacilli identify Brucella.
- D.
- Schistosomiasis is a fluke infection diagnosed by ova in stool or urine and does not produce bacterial growth on blood culture.
Reference: UpToDate 2025, Brucellosis: Epidemiology, microbiology, clinical manifestations, and diagnosis; Saudi MOH Communicable Disease Manual
This is one of 3,306 questions in the MedBoardSA SMLE bank, with timed test mode, tutor mode, and progress tracking by topic.
Practise the full bank