In a young adult woman with brucellosis presenting with fever, back pain, malaise, arthralgia, hepatosplenomegaly and sacroiliac joint involvement, what is the optimal duration of antimicrobial therapy?

Optimal Duration of Therapy for Brucellosis with Sacroiliac Joint Involvement

For this patient with brucellar spondylitis involving the sacroiliac joint (evidenced by back pain in the setting of confirmed brucellosis), the optimal treatment duration is 12 weeks (3 months), making the answer C.

Rationale for Extended Duration in Complicated Brucellosis

The presence of back pain and osteoarticular involvement fundamentally changes the treatment paradigm from uncomplicated brucellosis. 1, 2

• The IDSA guidelines explicitly recommend 3 months of antimicrobial therapy for patients with native vertebral osteomyelitis (NVO) due to Brucella species, which includes sacroiliitis 1
• Meta-analyses demonstrate that extending therapy to 12 weeks (rather than the standard 6 weeks) is the key factor that improves clinical outcomes in brucellar spondylitis 2
• The standard 6-week duration is reserved only for uncomplicated brucellosis without osteoarticular involvement 1, 2, 3

Clinical Context Supporting Extended Therapy

This patient has multiple features indicating complicated disease requiring prolonged treatment:

• Back pain in brucellosis should always raise suspicion for spondylitis or sacroiliitis, which occurs in 2-77% of cases with osteoarticular involvement 3
• The combination of fever, arthralgia, back pain, and hepatosplenomegaly with confirmed gram-negative coccobacilli (Brucella) and raw milk ingestion history is pathognomonic for brucellar spondylodiscitis 1, 3
• Even without MRI confirmation mentioned in this case, the clinical presentation warrants treatment as complicated disease 2

Preferred Antimicrobial Regimen

Aminoglycoside-containing regimens are superior to rifampicin-containing regimens for brucellar spondylitis: 1, 2

• Doxycycline 100 mg twice daily for 12 weeks PLUS streptomycin 15 mg/kg daily IM for 2-3 weeks (or gentamicin 5 mg/kg daily for 7 days) 1, 2, 3
• The aminoglycoside component provides superior efficacy compared to rifampicin-based regimens in spinal involvement 1, 2

Common Pitfalls to Avoid

Treating sacroiliac brucellosis with only 6 weeks of therapy results in unacceptably high relapse rates: 1, 2

• The 3-week duration (option A) is grossly inadequate and used only for post-exposure prophylaxis, not active disease 1
• Six weeks (option B) is insufficient for any osteoarticular involvement and increases treatment failure risk 1, 2
• Twenty-four weeks (option D) is excessive and reserved only for brucellar endocarditis or severe neurobrucellosis, not sacroiliitis 3

Monitoring and Follow-up

• Clinical improvement should be evident within 7-14 days of appropriate therapy 3
• MRI should be obtained if available to confirm sacroiliac involvement and assess treatment response 2, 3
• Relapse rates remain 5-15% even with optimal therapy, but relapses respond to the same regimen 3