A 54-year-old diabetic patient repos to his physician's office complaining of an unresolved skin lesion on his foot. The lesion began several weeks ago as a blister and has since become a painful, erosive, expanding sore. On examination, the affected site is now 5 cm in diameter, with a black necrotic center and raised red edges. Which of the following toxins has a mechanism of action most similar to the toxin responsible for tissue damage in this patient?

This patient's wound is infected with Pseudomonas aeruginosa, and the characteristic lesion described is called ecthyma gangrenosum. The Pseudomonas alpha toxin, which is responsible for the tissue damage, inhibits protein synthesis by acting on EF-2 with a primary target cell in the liver. The diphtheria toxin has a similar action, although its target cells are hea and nerve. Anthrax toxin is an adenylate cyclase that causes fluid loss from cells. Botulinum toxin is a neurotoxin that decreases acetylcholine synthesis. Cholera toxin acts to increase adenylate cyclase activity by ribosylation of GTP-binding protein. Ref: Brooks G.F. (2013). Chapter 16. Pseudomonads, Acinetobacters, and Uncommon Gram-Negative Bacteria. In G.F. Brooks (Ed), Jawetz, Melnick, & Adelberg's Medical Microbiology, 26e.