Understanding Yersinia: The Bacteria Behind Plague and Enteric Infections Yersinia bacteria consist of three main species, each causing different diseases in humans: Yersinia pestis, responsible for the plague; Yersinia enterocolitica, which infects the small and large intestines; and Yersinia pseudotuberculosis, causing abdominal pain and fever. Yersinia Pestis: Disease: The plague is an extrem..