Pertussis toxin mechanism — MRCPCH TAS MCQ

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ModerateMicrobiologyPertussis toxin mechanismMRCPCH TAS

A 7-week-old has paroxysmal cough, apnoea and lymphocytosis. PCR confirms Bordetella pertussis. What is the most likely toxin mechanism?

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Correct answer: C — Increased intracellular cAMP through Gi inhibition

Pertussis toxin ADP-ribosylates Gi proteins, increasing cAMP and contributing to lymphocytosis and respiratory symptoms. Inhibition of the 50S ribosomal subunit is an antibiotic mechanism, not pertussis toxin activity. The pearl is that young infants may present with apnoea rather than a classic whoop.

Reference: Nelson Textbook of Pediatrics; UKHSA Green Book; RCPCH Theory examination syllabi