A team of British and French researchers studied one resistant strain of the Mycobacterium tuberculosis microbe with newly developed techniques for molecular analysis and found the bacteria lacked a certain gene common to other forms of TB.
The researchers report the finding in the journal Nature, published today. One member of the team, Douglas Young, a Medical Research Council scientist at the Royal Postgraduate Medical School in London, said: 'This is the first time that anyone has got to the molecular basis of any form of drug resistance in TB.'
TB is the largest cause of death in the world from a single infectious disease. It is responsible for about one in four avoidable deaths in developing countries, and in recent years drug-resistant strains have appeared in many developed countries.
Doctors report that TB cases have increased by 33 per cent in Switzerland, 30.7 per cent in Denmark, 28 per cent in Italy and 11.8 per cent in the United States. Hospitals and prisons in the US have blamed drug-resistant forms of TB for a surge in the numbers of deaths from the disease.
The strain of TB the group studied is resistant to a drug called isonicotinic acid hydrazide, which has been central to the treatment of TB since the 1950s. The strain lacks a gene for a certain enzyme but the scientists do not yet understand how this confers resistance.
'This appears to be one way of getting resistance to one particular drug. It's just a start in explaining drug-resistance in TB,' Dr Young said.
At present it takes between 8 and 10 weeks to test for whether a TB infection is resistant to drugs, but the new research should lead to tests that give accurate results within days, he said.
Tuberculosis, which usually begins as a lung infection, flourishes in overcrowded conditions found among the poor and homeless and was thought to be largely eradicated in developed countries.
Barry Bloom, a medical researcher at the Howard Hughes Medical Institute in New York, says in Nature that many TB patients fail to complete their course of drug treatment, which has helped the development of drug-resistant strains. Without a significant effort to control the appropriate use of antibiotics, he says, 'we may be working our way back to a frightening future'.Reuse content