University of Central Florida probes what makes bacteria ‘flesh-destroying’

University of Central Florida researchers have found a novel genetic marker to discriminate between strains of a common bacteria in coastal waters that can cause deadly disease to humans and strains that don’t make people sick.

The findings, published recently in the journal Proceedings of the National Academy of Sciences, focus on Vibrio vulnificus, a potentially deadly bacteria that can enter the bloodstream via scratches and other open wounds. The researchers say their findings can help to predict the conditions that set the stage for future outbreaks from other pathogens.

"It's one of the fastest growing bacteria on earth that we know of," lead author Salvador Almagro-Moreno, an assistant professor of medicine at UCF, said of Vibrio. "I call them the hyenas of the ocean."

Vibrio vulnificus belongs to the same family of bacteria as those that cause cholera. It inhabits warm, salty waters such as the Indian River Lagoon and is part of a group of bacteria called "halophilic" because they require salt. It dies at salt levels typical in the ocean but thrives at lower to moderate salt concentrations, such as those found in the lagoon.

Vibrio vulnificus can cause infections in which the flesh around an open wound dies, giving the bacterium the name “flesh-eating.”

Not all the strains of the bacteria kill humans. Most cause no harm, Almagro-Moreno says. And the ecological and genetic reasons behind this drastic difference have remained a mystery for decades.

Eating raw oysters contaminated with the bacteria can cause the more severe life-threatening illness in those with underlying health conditions such as diabetes. 

Florida is entering the most dangerous time of year for the bacteria. Vibrio infections happen most often between May and October, according to the U.S. Centers for Disease Control and Prevention. Warm water and moderate salt levels can increase the amount of Vibrio in oysters and other shellfish.

“From COVID to V. vulnificus the emergence of human pathogens is one of the most concerning public health issues facing us,” Almagro-Moreno said. “But we know surprisingly very little about what triggers the change from harmless to deadly. We want to answer that question using aquatic pathogens such as the agent of cholera or V. vulnificus as model systems. Our study is a big step in understanding this emergence phenomenon, and will hopefully help us predict, prevent and manage future outbreaks.”

Almagro-Moreno collected samples between 2018 and 2019 from two areas of the lagoon, which stretches 156 miles from Volusia to Palm Beach County.

Before sampling, the team developed a novel genetic marker to screen different strains of the bacteria that can cause disease to humans and those that don’t.

“This accurate marker will aid in the detection of V. vulnificus globally, which we hope will be used by public health authorities to prevent or manage outbreaks” Almagro-Moreno said.

Read more: Florida health officials warn of deadly bacteria

Moreno’s team found links between the likelihood of identifying deadly strains of the bacteria and some environmental stresses.

“Our results indicate how ecosystems may be generating pressures that facilitate the emergence of specific strains with pathogenic potential within a natural population,” Almagro-Moreno said. “We now have evidence that the environment plays a most critical role in shaping the emergence of this pathogen. Nonetheless, we are pathogen hunters and there is much more research to conduct. But this is a critical starting point in solving the mystery of what are the elements/ingredients that make a pathogen?”

Vibrio infected eight Floridians in 2015, killing two, including a 57-year-old Melbourne man.

Florida health officials warn people to avoid exposing open wounds to warm, salty outdoor waters, and for those with health issues to avoid eating raw shellfish.

In early May 2015, a 57-year-old Melbourne man with a suppressed immune system died of a Vibrio infection. In late October of that same year, A 73-year-old Palm Bay man with diabetes and heart disease died of Vibrio after swimming in the Indian River Lagoon.

Health officials weren't able to determine whether either men had contracted the bacteria from food or through a wound.

The 57-year-old Melbourne man had eaten gumbo with oysters from a food store, but tests of the food were inconclusive. He also had eaten a fish he'd caught in the Indian River Lagoon, Inman said.

The 73-year-old man from Palm Bay had been swimming in the lagoon a few days before his death. But health officials could not say whether swimming or something he ate caused the infection.

Florida averages about 30 cases and nine deaths annually from Vibrio, according to Florida Department of Health data.

States in the Gulf Coast region average about 50 cases, 45 hospitalizations and 16 deaths annually, according to the Florida Department of Health. Most of the cases are in Florida.

While infections are rare, individuals should still take precautions, health officials say.

Infections in people with liver or immune system conditions have a 50% fatality rate.

When it infects the skin via open wounds, Vibrio releases a toxin that can cause skin breakdown and ulcers.

Ingestion of the bacteria can trigger vomiting, diarrhea and abdominal pain.

People with weakened immune systems, especially those with chronic liver disease, are the most at risk when they eat raw shellfish, especially oysters, health officials said, because oysters filter the bacteria from the water. Eating a single contaminated oyster can kill.

The bacteria rarely cause serious disease, and as a result is underreported, according to the CDC.

Illness usually begins within one to three days of exposure, but up to a week later for a small percentage of cases. Symptoms include fever, swelling and redness of skin on arms or legs, with blood-tinged blisters, low blood pressure and shock.

Learn about Vibrio vulnificus

Florida Department of Health Vibrio site: www.floridahealth.gov/diseases-and-conditions/vibrio-infections/vibrio-vulnificus/index.html

Tips for preventing Vibrio vulnificus infections

•Do not eat raw oysters or other raw shellfish.

•Cook shellfish (oysters, clams, mussels) thoroughly.

•For shellfish in the shell, either a) boil until the shells open and continue boiling for 5 more minutes, or b) steam until the shells open and then continue cooking for 9 more minutes. Do not eat those shellfish that do not open during cooking. Boil shucked oysters at least 3 minutes, or fry them in oil at least 10 minutes at 375°F.

•Avoid cross-contamination of cooked seafood and other foods with raw seafood and juices from raw seafood.

•Eat shellfish promptly after cooking and refrigerate leftovers.

•Avoid exposure of open wounds or broken skin to warm salt or brackish water, or to raw shellfish harvested from such waters.

•Wear protective clothing (e.g., gloves) when handling raw shellfish.

Source: Brevard County Health Department