Flesh-Eating Bacteria Like It Hot

Vibrio vulnificus bacteria. (Credit: Wikimedia Commons) It’s spring, and I’m attending a luxurious seafood banquet. Platters of shellfish fill the tables: crab with limbs akimbo; shrimp ready to be peeled; miniature lobster-like langostino peering at my dinner plate as if knowing their fate. Raw oysters sit in the center of the platter, piled absurdly high and shimmering luminescent on the half shell. Until now, I’ve never eaten a raw oyster. I apply a generous squirt of lemon juice and watch the white-grey flesh ripple ominously in reply. Tilting my head back, I down the shell’s contents in one shot of citrusy ocean. The gelatinous solid slides down my throat largely unchewed as I submit a silent prayer to the gods of food safety, asking not to become the subject of an ironic headline: “Research scientist studying bacterium found in raw oysters falls ill after eating…a raw oyster.” Thankfully, I walked away from the banquet without encountering Vibrio vulnificus, the bacterial subject of my Ph.D. Much as I want to be an academic expert on V. vulnificus, there are aspects of the microbe I hope never to attest to first-hand. But as the planet’s oceans heat up, the odds of a potentially fatal rendezvous will continue rise along with the temperature. Just as Zika caught researchers off guard, V. vulnificus could be the next public health threat that rapidly grows from a whisper to a shout. That’s why scientists, like me, are racing to understand this menacing microbe. High Stakes, High Costs V. vulnificus is a normal part of marine and estuarine environments, but it can travel from seawater into open wounds of swimmers, waders, or fishermen/women to instigate the flesh-eating skin disease necrotizing fasciitis. The bacteria also cause gastrointestinal (GI) infections when consumed in contaminated seafood – usually oysters. The microbes then have a propensity to escape the initial infection site and enter the bloodstream. That’s when trouble really starts, as dermatological or gastrointestinal symptoms give way to sepsis and multi-organ failure. Wound infections are lethal in more than 20 percent of cases, and foodborne infections, more than 50% of cases. Right now, the bacterium only causes about 100 foodborne infections in the United States each year, a number that pales in comparison to the roughly 1 million cases of foodborne Salmonella each year. Plus, most V. vulnificus cases occur in individuals with pre-existing medical conditions, like liver disease, which make them more susceptible to infection. Yet with its striking mortality rate, V. vulnificus is a grave health concern for those infected. And economically, the U.S. Department of Agriculture reports that, at $3.3 million per case, the 100 annual cases are responsible for more than $300 million in economic burden due to medical costs, productivity loss, and death. What’s more? These numbers are rising, and climate change may be to blame. Thermal Expansion V. vulnificus is bacterial cousin to the microbe that causes cholera and, similarly, thrives in temperate aquatic environments with moderate salinity. Bays and estuaries in the southeastern United States are perfect breeding grounds, particularly in the heat of summer. As climate change increases global ocean temperatures, the bacterium’s range is expanding to regions, such as Sweden and Finland, that were historically considered too cold to support the bacteria.