WASHINGTON — Cases of multidrug resistance in immigrant populations in the United States and links to the AIDS epidemic in Africa are attracting the attention of researchers.
“There is an erroneous assumption that tuberculosis has been eradicated,” Catherine D. DeAngelis, M.D., editor of the Journal of the American Medical Association, said at a press briefing on tuberculosis sponsored by JAMA.
“In fact it is a big problem, and should be taken seriously,” she said.
Of note, 407 cases of multidrug-resistant tuberculosis (MDR-TB) with specific resistance to at least isoniazid and rifampin occurred in a study of 28,712 tuberculosis cases in California from 1994 to 2003, according to Reuben M. Granich, M.D., of the Centers for Disease Control and Prevention in Atlanta, and his colleagues.
Patients with MDR-TB were seven times more likely to have reported prior tuberculosis treatment, compared with those with non-MDR disease, Dr. Granich said at the press conference.
In addition, 83% of the MDR-TB patients were born outside the United States, which highlights the need for both international control and improved screening, said Dr. Granich.
Prior treatment for tuberculosis was the strongest risk factor for MDR-TB in his study.
“There are two ways to develop MDR-TB,” Dr. Granich said.
One is through noncompliance with the treatment regimen, and the other is via airborne transmission from one patient to another, he said.
Once infected, the average lifetime risk for developing tuberculosis is 10%, and the risk is highest during the first 2 years after infection.
Most healthy people who are exposed to tuberculosis won't go on to develop the disease, and a person's state of health can modify the risk, Dr. Granich noted. For example, the risk of HIV/AIDS patients for developing tuberculosis increases significantly over that of a healthy person exposed to tuberculosis to an approximately 10% annual risk.
Of the 407 MDR-TB cases in Dr. Granich's study, 71 (17%) were resistant only to isoniazid and rifampin, and 86 (21%) were resistant to all four first-line drugs—isoniazid, rifampin, ethambutol, and pyrazinamide.
Most cases of tuberculosis are curable if patients are compliant and take the right medication for 6–9 months.
The “right medication” depends on the seropositivity of the patient's sputum sample, Dr. Granich said. However, cases of MDR-TB are highly complex, and require 18–24 months of therapy under the supervision of a specialist in order to achieve recovery, he noted.
The World Health Organization has stated goals of detecting 70% of new TB cases and successfully treating 85% of them, said Christopher Dye, D.Phil., at the press briefing.
The most significant barriers to achieving the goals set by WHO exist in Africa, where the HIV epidemic has led to an increased vulnerability to tuberculosis, and in Eastern Europe, where tuberculosis rates doubled during the 1990s, and multidrug resistance is high due to low compliance.
Dr. Dye and his colleagues reported that, with the exception of Africa and Eastern Europe, WHO can achieve its goals with increased application of the Directly Observed Treatment Scheme (DOTS).
This public health strategy that includes gaining political commitment, detecting cases based on sputum smear microscopy, utilizing standard short-course therapy with supportive patient management, ensuring regular drug supplies, and standardizing systems for recording cases and reporting outcomes (JAMA 2005;293:2767–75).
“There is a major education job to be done in terms of keeping tuberculosis on the agenda,” he said.
Another study in the same issue of JAMA found that isoniazid reduced the odds of developing a primary case of tuberculosis in a highly vulnerable population—1,655 male gold miners in Orkney, South Africa, who had previously tested positive for HIV.
After adjustment for age, calendar date, and silicosis grade in 1,041 individuals, there was a 46% reduction in tuberculosis incidence with isoniazid.
Only nine patients discontinued the drug because of adverse events (JAMA 2005;293:2719–25).