Brucella is a genus of gram negative, small, non-encapsulated coccobacilli which are strict aerobes.
Route of entry
- Ingestion of contaminated milk products
- Through the skin by direct contact
- Inhaled in aerosols
Pathogenesis
- Majority are killed by macrophages, rest survive in macrophages
- Invade the body through mucous of upper intestinal and respiratory tracts or skin lesions.
- Enter sub serosa and are transported by macrophages to lymph nodes of liver, spleen and bone marrow
- Enter bloodstream
- Host response is granulomatous, which progresses to focal abscesses
- Produce endotoxin but no exotoxin
Virulence factors
• Endotoxin
Predisposing factors • Inflected animals
• Unpasteurized milk
Clinical symptoms • Incubation period is 01-03 weeks • Fever is seen in minority of cases and it is undulating fever • Chills • Fatigue • Malaise • Anorexia • Weight loss • Enlarged spleen, liver, lymph nodes • Pancytopenia
• Osteomyelitis –a complication
Lab Diagnosis
Specimen • Blood
• Bone marrow
Microscopy • Gram negative • Small, coccobacilli • Non-encapsulated
• Strict aerobes
Brucella melitensis
Culture
Strict aerobes, requiring 5-10% CO2
Tryptone soya diphase medium
Produce variety of colonies, e.g smooth, mucoid, colourless or grey, white colonies
TSI agar
No H2S is produced
Biochemical Tests • Catalase +ve • Oxidase +ve • Indole -ve
• Hydrolyze urea
Serological tests • Slide agglutination test with Brucella antiserum. • Rapid IgM/IgG immunochromatographic assay
• PCR
Treatment
- Tetracycline
- No vaccine is available
Brucella – howMed
Brucella is a genus of gram negative, small, non-encapsulated coccobacilli which are strict aerobes.
Route of entry
Pathogenesis
Virulence factors
• Endotoxin
Predisposing factors • Inflected animals
• Unpasteurized milk
Clinical symptoms • Incubation period is 01-03 weeks • Fever is seen in minority of cases and it is undulating fever • Chills • Fatigue • Malaise • Anorexia • Weight loss • Enlarged spleen, liver, lymph nodes • Pancytopenia
• Osteomyelitis –a complication
Lab Diagnosis
Specimen • Blood
• Bone marrow
Microscopy • Gram negative • Small, coccobacilli • Non-encapsulated
• Strict aerobes
Brucella melitensis
Culture
Strict aerobes, requiring 5-10% CO2
Tryptone soya diphase medium
Produce variety of colonies, e.g smooth, mucoid, colourless or grey, white colonies
TSI agar
No H2S is produced
Biochemical Tests • Catalase +ve • Oxidase +ve • Indole -ve
• Hydrolyze urea
Serological tests • Slide agglutination test with Brucella antiserum. • Rapid IgM/IgG immunochromatographic assay
• PCR
Treatment