Vibrio vulnificus infection by eating oysters (molluscs).

Explanation

This fulminant infection gets people with damaged livers but can get others too. Usually the patient is an alcoholic or with chronic liver damage due to other reasons.

4-5 hours after exposure the patient will develop a purplish blister on the skin and go into cardiovascular collapse.

Drug of choice is Tetracycline. I have never seen a case but I do not live in New Orleans which is what the questions usually present.