That sounds reasonable. IIRC, Staph Aureus depends on aerobic respiration, as opposed to bugs that depend on anaerobic respiration.
The first thing that intrigued me was what genus the M. in M. ulcerans meant. It's Mycobacterium, the same genus in TB. Tuberculosis is the name of the species in TB.
PubMed had 43 articles on French clay, but none had pertinent titles. There was nothing on French green clay.
French green clay takes its name from the fact that rock quarries located in southern France enjoyed a virtual monopoly on its production until similar deposits of illite clays were identified in China, Montana, and Wyoming. The clay's green color comes from a combination of iron oxides and decomposed plant matter, mostly kelp seaweed and other algae.
OK, so the algae is probably still alive and thus probably "eats" the MRSA for its dinner. No joke.