Small Gram negative bacteria. Brucella. Small Gram negative, coccobacilli Non-motile, aerobic, non-fermentative Obligate intracellular Oxidase and catalase positive Visualised by Kosters (modified –ZN) stain Require growth on complex media
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1. Flood the slide with dilute carbol fuchsin and let it act for 5-7 minutes.
2. Wash with water.
3. Decolourise with 0.25% acetic acid for up to 30 seconds. The film should be colourless or very faintly pink.
4. Wash with water.
5. Counterstain with Loeffler’s methylene blue and leave for ½-1minute. Brucellae appear as little red bacilli singly, in pairs and in clusters.
Intracellular pathogen – many cell types
Survives within macrophages
Inhibits phagolysosome fusion
Tissue tropism - erythritol
Erythritol preferred carbon source
Present in high concentration in placenta of cattle, sheep, goats and pigs.
Siderophore, iron-uptakeBrucella pathogenesis
Exotoxin & adhisin
of B. bronchiseptica
to ciliated cells.
Tight adhesion to cilia.
Production of toxins.
Loss of cilia.
Interference with innate
and specific immune response.
Accumulation of mucus.