Brucella and Brucellosis PDF

# Brucella and Brucellosis - Overview of characteristics - Pathogenesis - Diagnosis - Prevention ## Characteristic Features - Short gram-negative coccobacilli - Aerobic and facultative intracellular pathogens - Primarily pathogens of animals ## Species of Brucella Infecting Humans 1. **Brucella...

# Brucella and Brucellosis - Overview of characteristics - Pathogenesis - Diagnosis - Prevention ## Characteristic Features - Short gram-negative coccobacilli - Aerobic and facultative intracellular pathogens - Primarily pathogens of animals ## Species of Brucella Infecting Humans 1. **Brucella abortus:** Infects cattle; causes abortion 2. **Brucella melitensis:** Infects sheep and goats 3. **Brucella suis:** Infects pigs - Transmission occurs through ingestion of contaminated milk and milk products and through handling of animals, including cows, pigs, and goats. - Human-to-human transmission is rare. ## Culture Characteristics - Grows on enriched media. - Brucella abortus requires 10% CO2 for growth. - Importance: Assists in diagnosis. ## Biochemical Reactions - Biochemical tests differentiate the *Brucella* genus and species. - It helps in definitive identification. | Bacteria | Test 1 | Test 2 | Test 3 | | :-------------------------- | :---- | :---- | :---- | | *B. melitensis* | - | - | + | | *B. abortus* | + | + | + | | *B. canis* | - | - | + | | *B. suis* | - | - | + | | *B. ovis* | + | - | + | ## Brucellosis - Also known as *Undulant Fever* or *Malta Fever*. - Zoonotic disease. - A map shows the global distribution of brucellosis. ## Modes of Transmission 1. **Ingestion:** Contaminated unpasteurized milk/products 2. **Direct contact:** Skin abrasions during handling of infected animals 3. **Inhalation:** Aerosols from infected animals or cultures ## Pathogenesis - This section includes a diagram outlining the pathogenesis of *Brucella*. - The diagram shows how Brucella enters the body, replicates in lymph nodes, and spreads to various organs. - *Brucella* is resistant to intracellular killing and evades the immune system. The bacteria grows in phagocytes, which spread to the *spleen, liver, lymph nodes, and bone marrow*. - The host then mounts a TH1 response, and granulomas are formed around the infection foci. ## Clinical Manifestations - **Symptoms:** Fever (undulant), chills, weakness, sweating, headache, and body aches. - **Findings:** Enlarged lymph nodes, liver, and spleen. - **Complications:** Osteomyelitis, endocarditis, and meningitis. ## Laboratory Diagnosis: Specimens - **A. Specimens:** Blood or bone marrow (acute illness) - **B. Cultivation:** Rare due to risk, long incubation (6-7 weeks) - **C. Serologic Diagnosis:** STAT: Detects IgM+ IgG antibodies - **ELISA for IgG or IgM** - **D. Brucellin Test:** Skin test for delayed hypersensitivity ## Prevention Strategies 1. **Pasteurization of milk and products** 2. **Control of animal infections** - **Vaccination with live attenuated vaccine (e.g., for cattle)**