What is the optimal duration of therapy for brucellosis with sacroiliac joint spondylitis in a 28‑year‑old woman presenting with fever, malaise, arthralgia, back pain, hepatosplenomegaly, anemia, thrombocytopenia, and Gram‑negative coccobacilli in blood culture?

Optimal Duration of Therapy for Brucellar Sacroiliac Joint Spondylitis

For this 28-year-old woman with brucellosis complicated by sacroiliac joint spondylitis, the optimal treatment duration is 12 weeks (3 months), making the correct answer C. 1, 2

Treatment Duration Based on Disease Severity

The key determinant of treatment duration is the presence of osteoarticular involvement, not the baseline uncomplicated disease. 2

• Uncomplicated brucellosis: 6 weeks of therapy is adequate 1, 3
• Brucellar spondylitis/sacroiliitis: 12 weeks of therapy is required 4, 1, 2
• Severe complications (endocarditis, neurobrucellosis): 24 weeks may be necessary 1

The IDSA explicitly recommends 12 weeks of antimicrobial therapy for native vertebral osteomyelitis caused by Brucella species, which includes sacroiliitis. 2 Meta-analysis data demonstrate that extending treatment from 6 weeks to 12 weeks markedly improves clinical cure rates in brucellar spondylitis. 1, 2

Why This Patient Requires Extended Therapy

This patient has clear evidence of osteoarticular involvement:

• MRI-confirmed sacroiliac joint spondylitis 2
• Back pain, which occurs in 2-77% of osteoarticular brucellosis cases 2
• Systemic features (fever, arthralgia, hepatosplenomegaly) consistent with complicated disease 2

A 6-week regimen is appropriate only for uncomplicated brucellosis without osteoarticular involvement, which this patient clearly has. 2

Recommended Antimicrobial Regimen

Aminoglycoside-containing regimens are superior to rifampicin-based combinations for spinal brucellosis. 4, 1, 2

The preferred regimen is:

• Doxycycline 100 mg orally twice daily for 12 weeks 2
• PLUS streptomycin 15 mg/kg intramuscularly daily for 2-3 weeks (or gentamicin 5 mg/kg daily for 7 days) 2

Common Pitfalls to Avoid

• 3 weeks (Option A) is inadequate: This duration is reserved only for post-exposure prophylaxis, not active disease 1, 2
• 6 weeks (Option B) is insufficient: While appropriate for uncomplicated brucellosis, it is associated with higher treatment-failure rates in osteoarticular involvement 2, 5
• 24 weeks (Option D) is excessive: This extended duration is unnecessary for sacroiliac disease and is limited to severe forms such as endocarditis or neurobrucellosis 1, 2

Supporting Evidence from Clinical Studies

Real-world data support the 12-week duration:

• A Chinese cohort of 590 patients demonstrated that 12 weeks of triple-drug therapy was effective for patients with osteoarticular complications, with an overall relapse rate of only 5.98% 6
• Pediatric studies showed that supervised combination chemotherapy for at least 6 weeks was effective in preventing relapse in uncomplicated cases, but osteoarticular brucellosis had higher relapse rates requiring longer therapy 5
• Historical data from Saudi Arabia confirmed that children with osteoarticular brucellosis had a higher relapse rate, necessitating extended treatment 5

Monitoring and Prognosis

• Clinical improvement should be evident within 7-14 days after initiating appropriate therapy 2
• Relapse occurs in 5-15% of patients even with optimal therapy, but relapses generally respond to the same antimicrobial regimen 1, 2
• MRI should be used to confirm sacroiliac involvement and assess treatment response 2