BACTERIA FOUND in a Madagascar boy appear to have acquired a set of five antibiotic-resistance genes, all at once, from another bacterial species.
A group of French researchers has identified the first case of bubonic plague resistant to multiple antibiotics, including the ones commonly given to treat it.
The case occurred two years ago in a 16-year-old boy in Madagascar. He survived when one of the three antibiotics prescribed to him proved effective, according to a report in today's New England Journal of Medicine.
The organism that afflicted the boy appears to have acquired a set of five antibiotic-resistance genes, all at once, from another bacterial species. Similar en bloc gene transfers have been implicated in the spread of drug resistance to other disease-causing bacteria, but never to plague, a disease synonymous with fatal epidemics.
Whether the Madagascar bacterium is rare or common is unknown. Although the report has no immediate public-health consequences, several experts said it symbolizes the growing problem of antibiotic resistance in human pathogens.
"Right now, it's just an isolated case," said David Dennis, an epidemiologist and plague specialist at the Centers for Disease Control and Prevention in Atlanta. "It's quite interesting. It also serves as a warning that we need to be aware of the emergence of antibiotic-resistant diseases and have the capabilities to detect, characterize and contain them."
"We now know this agent exists and have to be alert for it in other countries, where we know antibiotic resistance has emerged in so many other bacteria," said Stuart Levy, head of the Center for Adaptation Genetics and Drug Resistance at Tufts University's medical school in Boston.
Plague is caused by a bacterium called Yersinia pestis. It is generally transmitted to human beings by the bite of fleas that infest rodents carrying the disease. Bubonic refers to tender, swollen lymph nodes, called buboes, that are characteristic of the disease. Occasionally, the infection is passed from person to person through microscopic droplets made airborne by coughing. In that case, it is known as pneumonic plague.
Although plague epidemics have changed the course of history, the disease is relatively rare now. About 2,000 cases are reported worldwide each year, most of them in India and East Africa. Antibiotic treatment, if given early enough, can reduce the death rate from about 60 percent to 15 percent.
There were five cases of plague in the United States last year, two of them fatal, and there have been two cases, neither fatal, this year, Dennis said. The disease arrived in the United States through San Francisco in 1899. Since then, it has slowly moved east, harbored in populations of rats, voles, squirrels, prairie dogs and other rodents. It has never been detected in wild animal populations east of Dallas.
In response to the new report, CDC scientists recently tested several strains of plague taken from human patients in the United States. None was drug-resistant, Dennis said.