"In order to fulfill the criteria laid down in the remaining two of his postulates, Koch tried to infect animals with pure cultures of the organism with little success. He rightly concluded that the animals were not susceptible to cholera and took recourse to the extreme step of infecting himself by drinking pure cultures. However, he came down with only a mild episode of diarrhoea, an outcome which was later on exploited by his opponents to ridicule him."

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3089047/

Moreover, I believe the sentence preceding the quotation is incorrect and that v. cholerae is found in the stool of non-choleric individuals.