What is the antibiotic of choice for a patient diagnosed with brucellosis?

Antibiotic of Choice for Brucellosis

The optimal first-line treatment for uncomplicated brucellosis is doxycycline 100 mg twice daily for 6 weeks combined with streptomycin 15 mg/kg daily intramuscularly for 2-3 weeks, as this regimen demonstrates the lowest relapse rates. 1, 2, 3

Primary Treatment Regimens

First-Line Option (Preferred)

• Doxycycline-Streptomycin combination is the gold standard with superior efficacy compared to all other regimens 1, 2, 3
  • Doxycycline: 100 mg orally twice daily for 6 weeks 2, 3
  • Streptomycin: 15 mg/kg (approximately 1 g) intramuscularly daily for 2-3 weeks 2, 3
  • This combination has the lowest relapse rates (5-10%) among all treatment options 4

First-Line Alternative (When Streptomycin Unavailable)

• Doxycycline-Gentamicin offers comparable efficacy with the advantage of wider availability 2, 4
  • Doxycycline: 100 mg orally twice daily for 6 weeks 2
  • Gentamicin: 5 mg/kg parenterally once daily for 7 days (not a fixed 500 mg dose) 2
  • Failure/relapse rates are approximately 10-20%, only 5% higher than streptomycin-containing regimens 2
  • The World Health Organization endorses this as a first-line option 2

Second-Line Option

• Doxycycline-Rifampicin is acceptable but has higher relapse rates 1, 3, 4
  • Doxycycline: 100 mg orally twice daily for 6 weeks 2, 3
  • Rifampicin: 600-900 mg orally once daily (single morning dose) for 6 weeks 2, 3
  • Meta-analysis shows this regimen is inferior to doxycycline-streptomycin (OR = 3.17; 95% CI = 2.05-4.91) 4

Important Clinical Caveats

Public Health Consideration

• In regions where tuberculosis and brucellosis coexist, avoid rifampicin-containing regimens when possible to prevent emergence of mycobacterial resistance to this critical anti-TB drug 1, 2, 5
• The public health impact of rifampicin resistance may exceed the cumulative brucellosis morbidity 1

Treatment Duration

• Six weeks is the standard duration for uncomplicated brucellosis 2, 3
• Shorter durations (3 weeks) result in unacceptably high relapse rates 3
• Even with optimal treatment, expect 5-15% relapse rates, though relapses are typically mild and respond to the same regimen 2, 3

Complicated Brucellosis Modifications

• Brucellar spondylitis: Extend treatment to 12 weeks; aminoglycoside-containing regimens may be superior to rifampicin-containing ones 5, 3
• Neurobrucellosis: Consider doxycycline plus rifampicin with an aminoglycoside (preferably gentamicin) 5
• Brucellar endocarditis: Requires aggressive multi-drug therapy and often surgical intervention due to high mortality 3

Special Populations

• Pregnant women: Rifampicin 900 mg once daily for 6 weeks is the drug of choice (tetracyclines are contraindicated) 6
• Children <8 years: Use rifampicin plus trimethoprim-sulfamethoxazole for 45 days (avoid tetracyclines) 7, 6

Alternative Regimens (Cost-Effective Settings)

• Trimethoprim-sulfamethoxazole (800+160 mg twice daily for 6 weeks) may be used in resource-limited settings with response rates above 90% 2
• Quinolone-containing regimens (ofloxacin or ciprofloxacin) should be reserved as second or third agents in combination therapy 2, 8

Key Pitfall to Avoid

Never use monotherapy for brucellosis—all effective regimens require combination therapy to prevent relapse and treatment failure 1, 7, 9