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
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.