Scientists in the US claim to have discovered a multiple drug-resistant form of the much dreaded plague, one of the oldest and most lethal diseases in human history.
Tests on a strain of the disease-causing bacterium, Yersinia pestis, taken from a 16-year-old boy in Madagascar, revealed that the organism had developed resistance to eight antibiotics used to treat the infection, including streptomycin and tetracyclin.
The bacterium is believed to have become resistant to drugs after swapping genes with common food bacteria such as salmonella, E coli and klebsiella. Such bacteria are generally carried in the guts of fleas, which spread the disease by biting infected rodents.
A team lead by Timothy Welch at the US department of Agriculture analyzed genetic sequences from the drug-resistant plague microbe and compared them with similar sequences from food bacteria. They found a nearly identical 180-gene segment responsible for drug resistance in all of the organisms.
"The resistance is carried by these genes and they can transfer easily from one strain to another with very high efficiency," said Elisabeth Carniel, who co-authored the paper in the journal Public Library of Science One.
The discovery has alarmed scientists who fear multiple drug-resistant strains of the plague may emerge in other countries, leading to highly dangerous pandemics, which spread rapidly. Another serious concern is that drug-resistant strains of the organism may be collected by terrorist organizations and released into the air, causing widespread infection.
The plague first emerged several thousand years ago and swept across Asia and Europe during the Black Death pandemic between the 14th and 17th centuries. Successive pandemics are estimated to have claimed some 200 million lives.
Antibiotics brought the disease under control, but in recent decades the World Health Organization has recorded outbreaks in 125 countries. In the Democratic Republic of Congo, 1174 suspected cases were reported last year and there were deaths.