New UF technique may help quell cholera outbreaks

By Claudia Adrien

Photos by Dr. Gregory Gray

A new technique honed by University of Florida scientists can track rapid molecular changes that occur in cholera strains during epidemics. Researchers hope the genetic analysis will help stamp out such outbreaks.

The results of the UF study were published in the March issue of the journal Emerging Infectious Diseases.

Edsel Redden

In October, UF researchers from the College of Public Health and Health Professions, led by Edsel Redden, a faculty member in the department of environmental and global health, went to Haiti during the cholera outbreak to collect stool samples from 19 patients suffering from severe diarrhea at St. Marc’s Hospital in Léogâne. People infected with the cholera bacterium, a waterborne organism that attacks the small intestine, often experience rapid dehydration that can lead to death if untreated.

The samples were examined at UF’s Emerging Pathogens Institute, where researchers used a molecular typing, or fingerprinting, technique that follows rapidly changing areas of the cholera genome. Most molecular fingerprinting methods have difficulty detecting differences in the type of cholera bacterium found in the patient samples.

The researchers examined 187 bacterial colony selections and showed that even in individual patients, the DNA sequences were beginning to diversify. It’s a remarkable finding, they say, because although all the isolates can be traced back to a single cholera clone introduced into Haiti, the molecular signature is changing as the epidemic progresses.

Following strains with these unique signatures allows researchers to see, almost in real time, how the disease is spreading, whether through contamination of surface water, food or from human travel.

Dr. Afsar Ali

 “Although there are changes happening in the Haitian strains, we have also confirmed that there’s little diversity in them,” said Afsar Ali, Ph.D., a research associate professor in the department of environmental and global health and member of the UF Emerging Pathogens Institute, who was lead author of the paper. “This is significant because it means there was a single introduction of a cholera strain into the country.”

The UF researchers have drawn no conclusions that cholera came into Haiti through Nepali United Nations peacekeepers stationed in the country, as suggested in some media reports.

“It appears that the first several cases of cholera had resulted from people drinking contaminated river water, and water should be considered the major driver of the cholera epidemic in Haiti,” Ali said. “However, it’s yet to be validated that the introduction of the cholera germ in the water happened via human fecal excretion.”

Redden is overseeing construction of a UF research laboratory in Léogâne, which will help scientists analyze infectious bacteria, viruses and parasites in Haiti rather than shipping samples to the United States.

“Cholera spreads quickly through contaminated food and water and can survive in the environment,” said Judy Johnson, Ph.D., one of the paper’s authors, a UF College of Medicine professor and member of the Emerging Pathogens Institute. “Tracking the spread in real-time, at a community level, is essential in helping identify sources of contamination so that they can be eliminated, stopping the spread of disease before it gets worse.”

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Summer 2011

New UF technique may help quell cholera outbreaks

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