Brucellosis Diagnosis and Treatment

Diagnostic Approach

• The diagnosis of brucellosis should be established through blood cultures (2 sets) combined with serological testing, with bone marrow culture reserved for cases where blood cultures are negative despite high clinical suspicion 1
• Blood cultures (2 sets) are essential and should be obtained in all suspected cases, with sensitivity ranging from 15-70% depending on laboratory practices and requiring prolonged incubation up to 4 weeks 1
• Serological testing using standard tube agglutination (STA) is the most widely used confirmatory test, with titers ≥1:160 considered diagnostic when combined with compatible clinical presentation 2, 1
• Baseline inflammatory markers including ESR and CRP should be obtained, as mild transaminitis and pancytopenia are commonly observed 3, 1
• Patients presenting with fever and epidemiologic risk factors, such as consumption of unpasteurized dairy products, occupational exposure, or residence in endemic areas, should be considered for brucellosis diagnosis 4, 1
• Subacute presentations with low-grade relapsing fever, lymphadenopathy, hepatosplenomegaly, or osteoarticular complications should also be considered for brucellosis diagnosis 4, 1
• Returned travelers from endemic regions presenting with fever of unknown origin should be evaluated for brucellosis 4
• Bone marrow culture has the highest sensitivity and is considered the investigation of choice when blood cultures are negative 1
• In endemic settings with suspected vertebral osteomyelitis, strongly positive Brucella serology (≥1:160) combined with compatible imaging obviates the need for image-guided biopsy 5, 2
• For suspected brucellar vertebral osteomyelitis, obtain blood cultures and Brucella serology in all patients with subacute vertebral osteomyelitis residing in endemic areas 3
• MRI of the spine is the imaging modality of choice (97% sensitivity, 93% specificity) for suspected brucellar vertebral osteomyelitis 3
• Avoid image-guided biopsy if blood cultures are positive for Brucella or if serology is strongly positive (≥1:160) in endemic settings 5, 2
• Blood culture requests should be discussed with the laboratory beforehand, as initial processing requires special biosafety level 3 precautions due to risk of aerosolized transmission to laboratory workers 4, 1

Treatment Recommendations

• The World Health Organization recommends first-line treatment for uncomplicated brucellosis as doxycycline 100 mg twice daily for 6 weeks combined with either streptomycin 15 mg/kg daily IM for 2-3 weeks OR gentamicin 5 mg/kg daily IV for 7 days 6
• Doxycycline + Streptomycin: Doxycycline 100 mg PO twice daily for 6 weeks PLUS streptomycin 15 mg/kg IM daily for 2-3 weeks (lowest relapse rate) 6
• Doxycycline + Gentamicin: Doxycycline 100 mg PO twice daily for 6 weeks PLUS gentamicin 5 mg/kg IV daily as single dose for 7 days (WHO-recommended, comparable efficacy with wider availability) 6
• Doxycycline + Rifampicin: Doxycycline 100 mg PO twice daily for 6 weeks PLUS rifampicin 600-900 mg PO daily for 6 weeks (alternative when aminoglycosides contraindicated) 6
• Trimethoprim-sulfamethoxazole (TMP-SMX) 800+160 mg twice daily for 6 weeks may be used as a cost-effective alternative in resource-limited settings or as a third agent in complicated cases 7, 6
• Fluoroquinolone-containing regimens (ofloxacin or ciprofloxacin) should be reserved as second or third agents due to higher cost and risk of promoting antimicrobial resistance 7, 6
• Standard treatment duration is 6 weeks for most regimens 6
• Relapse rates range from 5-15% even with appropriate treatment, but relapses are usually mild and respond to the same regimens 6
• In regions where brucellosis and tuberculosis coexist, consider public health implications of rifampicin use, as this may contribute to mycobacterial resistance 6, 8
• For neurobrucellosis or brucellar spondylitis, aminoglycoside-containing regimens may be superior to rifampicin-containing ones 8
• MRI should be performed when spinal involvement is suspected 8
• Immobilization is crucial for cervical involvement to prevent devastating neurological complications 8