Chapter 7, Problem 1EDCS

Emerging Disease Case Study Vibrio Vulnificus Infection

Greg enjoyed Florida’s beaches; swimming in the warm water was his favorite pastime. Of course, the salt water did sting his leg where he had cut himself on some coral, but it didn’t sting enough to stop Greg from enjoying the beach. He spent the afternoon jogging in the pure sand, throwing a disc, watching people, drinking a few beers, and of course spending more time in the water.

That evening, he felt chilled, a condition he associated with having gotten too much sun during the day, but by midnight he thought he must have caught a rare summertime flu. He was definitely feverish, extremely weak, and tired. His leg felt strangely tight, as though the underlying muscles were trying to burst through his skin.

The next morning, he felt better, except for his leg. It was swollen, dark red, tremendously painful, and covered with fluid-filled blisters. The ugly sight motivated him to head straight for the hospital, a decision that like y saved his life.

Greg was the victim of an emerging pathogen, Vibrio vulnificus–a slightly curved, Gram-negative bacterium with DNA similar to that of V cholerae (cholera bacterium). V vulnificus lives in salty, warm water around the globe. Unlike the cholera bacterium, V vulnificus is able 10 infect a person by penetrating directly into a deep wound, a cut, or even a tiny scratch. In a person, the multiplying bacterium secretes quorum-sensing molecules. When the cells sense that there is a certain population size (a quorum), they “turn on” some of their genes, allowing them to thrive in the body and cause disease

Greg’s doctor cut away the dead tissue and prescribed doxycycline and cephalosporin for two weeks. Greg survived and kept his leg. Half of the victims of V. vulnificus are not so lucky; they lose a limb or die. Who knew that a beach could be so dangerous? (For more about quorum sensing, see pp.167-169.)

1. 1. Why is it necessary for Vibrio vulnificus to turn on different genes when the microbe invades a human?
2. 2. What does the term “turn on” mean in relation to transcription and translation?
3. 3. Why do you think the related microbe V. cholerae is unable to infect through the skin?