An 8 month old baby presents to the emergency room with a 1-day history of poor feeding and generalized weakness. The mother states that she often feeds the baby honey to pacify her. The toxin responsible for this presentation works by which of the following mechanisms?
The clinical history suggests infant botulism. The clue here is that the mother feeds the baby honey. Clostridium botulinum (a common honey contaminant) was ingested and produced toxin in the infant. The toxin, which blocks the release of acetylcholine from nerve terminals, is responsible for the floppiness. Acetylcholine is the neurotransmitter at the neuromuscular junction and impairment of this can lead to muscle weakness, failure to thrive, and in more serious cases, respiratory impairment. Glycine and GABA release is inhibited by C. tetani. This leads to the muscular spasms of tetanus. ADP-ribosylation of an elongation factor is a mechanism of action of diphtheria and Pseudomonas exotoxins. Alpha toxin from C. perfringens is a lecithinase responsible for the development of gas gangrene. Ref: Ray C.G., Ryan K.J. (2010). Chapter 29. Clostridium, Peptostreptococcus, Bacteroides, and Other Anaerobes. In C.G. Ray, K.J. Ryan (Eds), Sherris Medical Microbiology, 5e.
It blocks the release of acetylcholine from the nerve terminal
It blocks the release of inhibitory neurotransmitters such as glycine and GABA
It has a subunit that inactivates an elongation factor by ADP-ribosylation
It is a lecithinase