Brucella melitensis
From IDWiki
Background
- Causes brucellosis, also called Malta fever
Microbiology
- Facultative intracellular, Gram-negative coccobacillus
- Catalase positive, oxidase positive, nitrate positive, and urease positive
- Non-motile
- Risk group 3 organism
- When suspected, plates should be sealed and it should not be set up for mass spectrometry
Epidemiology
- Zoonotic transmission transmitted by ingesting contaminated food (such as unpasteurized milk products), direct contact with an infected animal, or inhalation of aerosols
Clinical Manifestations
Brucellosis
- Exposure to unpasteurized milk products or animals
- A common cause of fever without a focus in endemic countries
- Undulating fever
- Headache, arthralgia, night sweats, fatigue, anorexia
- Arthritis, spondylitis (especially sacroiliac and other large lower-extremity joints), osteomyelitis
- Hepatomegaly, splenomegaly, and lymphadenopathy
- Orchitis and epididymitis, prostatitis, and tubo-ovarian abscess
- Foul-smelling sweat
- Can have mild pancytopenia
Relapsed Brucellosis
- Occurs within six months of completing treatment in about 10% of patients
Diagnosis
- Culture
- May be isolated from blood culture, but only intermittent and is a fastidious organism
- Sensitivity is 50-70%
- Cultures should be held for 10 days
- Grows slowly on blood and chocolate agar; better on Brucella agar
- On gram stain, the small coccobacilli look like fine grains of sand
- May be isolated from blood culture, but only intermittent and is a fastidious organism
- Serology
- Acute and convalescent serology showing a fourfold rise in titres
- Serum agglutination test titres of 1:160 or greater in the right clinical context
- Cross-reacts with Francisella tularensis and Vibrio cholerae
Management
Prevention
Lab Safety
- Assess risk and provide prophylaxis and monitoring per CDC guidelines
- Assess risk
- Minimal risk
- Manipulating routine specimen or enriched material in BSL2 with PPE
- Being present while someone manipulates a routine specimen in BSL2, or on an open bench without aerosol-generating procedures
- Manipulating or being present while someone manipulates enriched material in BSL2
- Low risk
- Being present more than 5 feet from someone manipulating enriched material on an open bench, without aerosol-generating procedures
- High risk
- Manipulating a routine specimen resulting in contact with broken skin or mucous membranes
- Being present less than 5 feet from someone manipulating enriched material outside of a BSL2
- Manipulating enriched material within a BSL2 without PPE
- Being present in the lab during an aerosol-generating procedure
- Minimal risk
- Aerosol-generating procedures include centrifuging without sealed carriers, vortexing, sonicating, spillage/splashes
- Enriched material includes positive blood cultures, and reproductive clinical specimens (amniotic fluid, placental products) should be treated similarly
- People with high-risk exposures should have post-exposure prophylaxis and follow-up
- PEP with doxycycline 100 mg PO bid plus rifampin 600 mg PO daily for 21 days
- Either can be replaced by TMP-SMX if contraindications exist, but should ensure two effect antibiotics are used
- Follow-up
- Daily fever checks and weekly symptom watch for 24 weeks after last known exposure
- Serial serology at 0, 6, 12, 18, and 24 weeks after last known exposure
- PEP with doxycycline 100 mg PO bid plus rifampin 600 mg PO daily for 21 days
