He was interested in a disease called bacillary dysentery, which is a bacterial infection that causes severe diarrhea, and back then, was actually killing a lot of people, because after all, no cure for bacterial infections had been invented.
Ele estava interessado em uma doença  chamada disenteria bacilar, uma infecção bacteriana que causa diarreia grave e que, na época, estava matando muita gente, afinal de contas, não havia cura para infecções bacterianas.