The viable but non-culturable state in the human pathogenVibrio vulnificus

Vibrio vulnificus is a serious human pathogen, accounting for 95% of all seafood-related deaths in the United States. During the winter months, when coastal water temperatures drop below 10 degrees C, investigators have repeatedly reported their inability to isolate this estuarine bacterium from the environment. We now realize that this apparent 'die-off' is actually due to entry of the cells into a 'viable but non-culturable' state, a survival response to the low temperature stress. Cells in this state appear dormant, and cannot be cultured in or on routine bacteriological media, but are capable of returning to the actively metabolizing state when the environmental stress is removed. This review describes this non-culturable state in V. vulnificus, and its role in the ecology, physiology, and epidemiology of this pathogen.