By Mark Nolte
Using population genetics, a BYU researcher and two Johns Hopkins University scientists aim to redefine the way infectious diseases are tracked and combated.
Keith Crandall, associate professor of integrative biology, microbiology and molecular biology, is using his evolutionary expertise to analyze the sexually transmitted bacterium neisseria gonorrhoeae.
“It”s one of those diseases that shouldn”t be here,” Crandall said. “The reason we can”t get rid of it is because we can”t keep up with it.”
Through their research, Crandall and his Johns Hopkins colleagues; Raphael Viscidi, associate professor of pediatrics; and Jonathan Zenilman, associate professor of medicine and gynecology, hope to put an end to gonorrhea”s stubborn persistence.
Traditionally, infectious diseases like gonorrhea have been identified through behavioral or geographical cues.
For example, an epidemiologist, someone who studies the spread of diseases, may label a population of people as “infected” if common behaviors associated with a disease are detected.
Populations that have stable geographical or behavioral clues are called core populations. Populations that display waxing and waning disease are termed peripheral populations.
According to Viscidi, the criteria for establishing population types are subjective.
“The current way of tracking infectious diseases is not working well,” Crandall said. “Our proposed solution is to track it through population genetics.”
Employing skills from population genetics, the research team can recognize different strains of gonorrhea bacteria.
If the team were successful, for example, in identifying variation A, B and C of a gene, then they could more objectively characterize a population.
“We”re saying that we should look at the core population from the organism”s (gonorrhea) point of view,” Viscidi said.
Core population members that have received treatment, like penicillin, yet continue to welcome infectious diseases through activities such as intravenous drug-use or sexual promiscuity can be re-infected with gonorrhea.
The cycle of “treatment-then-re-infection” may lead to greater genetic variation within the core populations because gonorrhea bacteria have time to mutate into strains that resist treatment, the research team said.
In peripheral populations, however, the cycle is not present, and the gonorrhea strains will not be as diverse because treatment should eradicate them, and re-infection will be minimal.
If Crandall”s skill in evolutionary biology helps identify genetic markers that correlate with risk factors, then core populations will be better defined and public health officials will know where to focus their treatment efforts. Knowledge gained from this project could also be used in tracking HIV.
Funded by a grant from the National Institutes of Health, Crandall and his team are collecting data in Baltimore.
They have completed their first year of research and plan to continue the project until 2007.
With his feet in two departments, his role as a graduate advisor and four more years of gonorrhea research, Crandall keeps up a rigorous academic schedule.
“He certainly wears lots of hats, and does it well,” said Alan Harker, Microbiology and Molecular Biology Department chair. “He is a workhorse.”
