KROK 1 2010 – Question 46 · KROK (Medicine) · Microbiology, Virology, and Immunology
In order to determine toxigenicity of diphtheria bacilli a strip of filter paper impregnated with antitoxic diphtherial serum was put on the dense nutrient medium. There were also inoculated a microbial culture under examination and a strain that is known to be toxigenic. If the microbial culture under examination produces exotoxin, this will result in formation of:
- A. Zones of lecithovitellinous activity
- B. Haemolysis zones
- C. Precipitin ring
- D. Zones of diffuse opacification
- E. Precipitin lines
Hint
Think about what becomes visible in the gel when a toxin diffusing from the colonies meets its specific antitoxin diffusing from the paper strip, and compare it with other visible effects on culture media.
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