Systemic Bacteriology · NEET PG Preparation Microbiology
A 24-year-old medical student develops a sore throat, low-grade fever, and malaise. Examination of the posterior pharynx reveals a dirty-gray, firmly…
Practice question from Systemic Bacteriology (NEET PG Preparation Microbiology), with the correct answer and a step-by-step solution.
medium · MCQ · Q-409656
A 24-year-old medical student develops a sore throat, low-grade fever, and malaise. Examination of the posterior pharynx reveals a dirty-gray, firmly adherent pseudomembrane that bleeds upon scraping. Cervical lymphadenopathy gives a 'bull-neck' appearance. Which laboratory finding or test is most specific for confirming the mechanism of pathogenesis of this organism?
- A.Elek gel diffusion test for in vitro toxin productionCorrect answer
- B.Nagler reaction detecting lecithinase activity
- C.Quellung reaction showing capsular swelling
- D.CAMP test showing an arrowhead zone of hemolysis
Solution
Corynebacterium diphtheriae causes diphtheria through the production of an exotoxin encoded by a beta-phage (eta-toxin). The Elek test is a standard immunodiffusion assay used to demonstrate toxigenicity in vitro. The Nagler reaction is used for Clostridium perfringens, the Quellung reaction for encapsulated organisms like Streptococcus pneumoniae, and the CAMP test for Streptococcus agalactiae.
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