I would not agree that the vomiting reflex doesn’t protect the animal. Clearly, the sooner the irritating substances are cleared of the gastrointestinal tract, the better for the animal’s health. The animal doesn’t have to « know » anything to be protected by a reflex, just like taking your hand off the hot stove protects you before the brain event feels the heat.

I would also not agree that the vomiting reflex of animals was evolved by the microorganisms, because that’s not how evolution works. The development of the sensory apparatus needed to sense the irritation, and then to provoke the necessary contractions to induce the vomiting is the result of the animal (not the microorganisms) population’s genetic changes and selection, with the animals that developed that reflex being fitter to face off infections.

I’ll agree that some microorganisms may have evolved to produce increasingly irritating substances so as to provoke vomiting with evermore efficiency because this could benefit them with the dispersion aspect.