You have just received an urgent call from the Centers for Disease Control and Prevention (CDC) to consult on the following case of an unusual disease outbreak that they have been investigating. A new...

You have just received an urgent call from the Centers for Disease Control and Prevention (CDC) to consult on the following case of an unusual disease outbreak that they have been investigating. A new gram-positive bacterium related to Listeria monocytogenes was isolated from an outbreak of food poisoning in Wisconsin due to contaminated cheese and appears to cause painful gastritis and in about half of exposed individuals, along with sudden onset of bleeding ulcers, death from toxic shock within 2 or 3 days. Upon biopsy of infected individuals, it was found that the bacteria were growing on the surfaces of epithelial cells lining the gastric pit of the stomach. Autopsy of individuals who died showed that bacteria were found only in the stomach and not in any of the other body organs. The researchers at the CDC have subsequently determined that, like L. monocytogenes, this new species of Listeria invades epithelial cells in tissue culture. Which, if any, of Koch’s postulates have been satisfied for the involvement of this new Listeria strain in gastritis, bleeding ulcers, and toxic shock? What additional measures could the researchers take to help satisfy Koch’s postulates?