BRUCELLA

Brucella

Morphology of Brucella

• Brucella is a genus of Gram-negative, facultative intracellular bacteria.
• They are small, non-motile, non-spore forming, and pleomorphic rods.
• They have a thick cell wall containing lipopolysaccharides.
• Brucella species are typically 1-2 microns in length and 0.5-1 micron in width.

Pathogenesis of Brucellosis

• Brucella species are transmitted to humans through direct contact with infected animals or their products (milk, meat, etc.).
• The bacteria enter the host through skin abrasions, mucous membranes, or ingestion.
• Once inside the host, Brucella species invade and survive within the phagosomes of macrophages and dendritic cells.
• They multiply within these cells and eventually escape into the cytoplasm, where they form a replicative vacuole.
• Brucella species then release proteins that help them evade the host's immune system and replicate within the host.

Life Cycle of Brucella

1. → Brucella species are ingested by the host through contaminated animal products.
2. → The bacteria invade and survive within the phagosomes of macrophages and dendritic cells.
3. → They multiply within these cells and eventually escape into the cytoplasm.
4. → Brucella species form a replicative vacuole and release proteins that help them evade the host's immune system.
5. → They replicate within the host and cause disease.

Laboratory Diagnosis of Brucella

• Isolation of Brucella species from blood, bone marrow, or other tissues.
• Serological tests (e.g., ELISA, IFA) to detect antibodies to Brucella species.
• PCR (Polymerase Chain Reaction) to detect Brucella DNA.
• Culture of Brucella species on selective media (e.g., Brucella agar).

Memory Trick: "Brucella is a sneaky bug, it hides in the cells, and then it's free to multiply, and causes disease in you and me!"

Note: This memory trick is to help remember the life cycle of Brucella.