What is drug-resistant TB?
Tuberculosis, caused by Mycobacterium tuberculosis, is one of the most common communicable diseases in India, its transmission fuelled by unhygienic, crowded living conditions. If the bacterium is exposed to a non-lethal dose of antibiotics combination - which can happen if a patient starts a course of medication but does not finish it - it can become unresponsive to those antibiotics. The infection is then said to have become drug resistant.
How bad can this condition get?
Depending on responsiveness to basic and advanced antibiotics - referred to in medical parlance as first-, second-, and third-line drugs - drug resistant TB is classified as 'multi-drug resistant' (MDR), 'extensively drug resistant' (XDR) and, recently, 'totally drug resistant' (TDR). MDR TB is resistant to at least two of the first line TB drugs, Isoniazid and Rifampicin. When in addition, it is also resistant to fluoroquinolones and at least one of three injectable second-line drugs, viz., Amikacin, Kanamycin and Capreomycin, the infection is categorised as XDR. TDR shows resistance to all tested first- and second-line drugs - Isoniazid, Rifampicin, Streptomycin, Ethambutol, Pyrazinamide, Ethionamide, para-aminosalicylic acid, Cycloserine, Ofloxacin, Amikacin, Ciprofloxacin, Capreomycin and Kanamycin.
What are the possible sites of TB infection in the body?
While pulmonary or lung TB is the commonest and most virulent form of the disease, the baterium can, in fact, infect a vast range of organs in the body, including the brain, bones, lymph nodes, spinal cord and abdomen. These forms of TB are not as contagious as pulmonary TB, though many of them have a prior history of lung infection. Non-pulmonary tuberculosis is also difficult to diagnose, because there are no clear-cut guidelines.
How common is drug resistant TB in India?
According to WHO data, in 2013, a total 14,15,617 cases of TB were notified, some of which were relapses and, therefore, strong suspects for drug-resistance. Of the new cases, 2.2% were of MDR TB. A total of 20,763 patients were started on MDR TB treatment that year. Consolidated prevelance data for XDR TB is harder to find, but reviews in various institutes found 2.4%-5% of MDR cases could turn out to be XDR. Incidence figures for TDR TB are not available.
How is India tackling drug-resistant TB?
Directly Observed Treatment, Short Course (DOTS) has been India's most effective weapon. While treatment must continue for between 6 months and two years, as both results and side-effects - such as impaired liver function - start to show within a month or two, some patients discontinue the medication. Treatment is sometimes also interrupted due to factors such as poverty and unemployment. The DOTS strategy ensures that patients are diagnosed and treated effectively until they are cured,
by ensuring the availability of the full course of drugs, and by monitoring patient compliance. The medicine is administered in the presence of a health worker. The effort has been to get patients from private practitioners to government health centres.
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