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The results of the Mexican study strongly suggest that DOTS reduces
transmission of resistant strains by curing potential multi-drug resistant cases
of TB.
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A standard and inexpensive tuberculosis treatment regimen cut the
overall TB rate in half and lowered the rate of drug-resistant cases
even more dramatically in a remote Mexican health district with a high
prevalence of the disease. ?This shows what basic TB control can
accomplish,? said Maria de Lourdes Garc? Garc?, a Howard Hughes
Medical Institute international research scholar who led the Mexican
study.
To learn more about TB transmission in less developed
countries, Garc? Garc? and colleagues from the National Institutes of
Mexico and Stanford University launched a five-year study in the Orizaba
Health Jurisdiction, four hours by bus southeast of Mexico City. The
district, which has a higher rate of TB than Mexico as a whole,
encompasses five mostly urban communities in an industrialized valley
and surrounding rural mountains.
?This shows what basic TB control can accomplish.?
Maria de Lourdes Garcia Garcia
Supported by HHMI, the U.S. National Institutes of Health, and the
Wellcome Trust, the study used modern molecular epidemiologic
approaches, in addition to screenings, clinical assessment of people
reporting symptoms, supervised treatment, and follow-up, to explore a
global health problem.
At the outset, 22 percent of previously untreated patients with
pulmonary TB were carrying drug-resistant strains, and 6.7 percent had
multiple-drug resistance. By the study's final year, only 7.8 percent of
new TB patients carried drug-resistant strains, and there were no cases
of multiple-drug resistant TB.
The researchers report their findings in the April 2, 2005 issue of the
British medical journal The Lancet. A commentary by Marcos Espinal,
executive secretary of the World Health Organization's Stop TB
Partnership, appears in the same issue.
People with TB must take four standard drugs daily for six months. They
may begin to feel better after a month, which tends to lead them to skip
doses, but if they stop taking the drugs for any reason, the drugs may
become ineffective and multi-drug resistant TB may result. Multi-drug
resistance refers to resistance to two of the most powerful anti-TB
drugs, rifampicin and isoniazid. Overcoming this drug resistance is a
major goal of public health programs fighting TB.
When Garc? Garc?'s study began in 1995, regional health officials in
Mexico had begun to upgrade their TB treatment program to a World Health
Organization model called directly observed therapy (DOTS). The
five-pronged strategy of DOTS includes political commitment to the
eradication of TB, case detection by sputum microscopy, supervised
administration of drugs for at least the first two months of treatment,
an uninterrupted supply of all essential drugs, and a rigorous
assessment of treatment and outcomes.
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The results of the Mexican study ?strongly suggest that DOTS reduces
transmission of resistant strains by curing cases of TB that otherwise
could become multi-drug resistant if they are not properly treated,?
said Marcos Espinal, executive secretary of the Stop TB Partnership at
the World Health Organization. ?This study shows that DOTS is needed to
control multi-drug resistance. Without DOTS, measures directed to
multi-drug-resistant TB will not work.?
The unexpected effectiveness of DOTS in reducing the transmission of
multi-drug-resistant TB in the Orizaba region of Mexico underscores the
importance of a global strategy for tackling the TB pandemic, said
Garc? Garc?, director of the tuberculosis unit of Mexico's National
Institute of Public Health and corresponding author of The Lancet paper.
?The fact that DOTS can control drug-resistant tuberculosis is some of
the best news in recent years for the field of TB control,? she added.
?It is also an urgent call for the world to do more with the
cost-effective interventions already at our disposal.?
Fewer people may catch the drug-resistant form of the deadly infectious
disease, but those who do are more likely to die without second-line
drugs, which tend to be more expensive, Garc? Garc? and her colleagues
noted. The study demonstrates the need for a new supplemental public
health strategy to provide additional drugs for people with resistant
strains, said Garc? Garc?.
?We need both?DOTS to cure the majority of cases, so the transmission of
some drug resistant strains is stopped, and DOTS-Plus to manage patients
with multiple-drug resistance, which requires special drugs " said
Espinal, who wrote an accompanying editorial in the same issue of The
Lancet.
The Orizaba study complied with the ethical guidelines for research in
less developed countries by providing the standard of care recommended
for
98 percent of the world's TB patients. Since then, a study in Peru
reported better outcomes when patients with multi-drug resistant TB were
given individualized, supervised therapy. ?The international research
community still needs to come to an agreement about what extra care
should be provided to study participants with multi-drug resistant TB,?
Garc? Garc? and colleagues wrote in The Lancet paper.
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