Tuberculosis is an impotant disease of coming time although controlled by modern medicines but drug resistant TB as Multidrug resistant Tuberculosis (MDRT) or XDRT (Extreme durg resistant TB) are very dangerous for developing and developed countries both as no drug can take care of it , so once spread in society , it will cause extensive damge both mortality and morbidity will increase .The main reason behind this is a fact to detect TB in early stage once TB bacilli are not secreted or expelled out in Sputum because to detect TB bacilli in pus,blood,serum, csf,semen, vaginal fluid, stool, swaet, urine , peritoneal or pericardial or plueral fluid is almost very difficult and as by simple AFB staining it is not visible then we have to go for culture which takes about 4-6 wks either by inocculation in guinea pig or different recetly developed cultural media and recently developed Bactec Method of incubation also takes 07 days ,and to determine culture and sensitivity is again time lasting costly herculian task, ADA testing of fluid provide indirect evidence, PCR TB is very costly and requires good time and is selectively avaiable in few centre in India so mostly TB is diagnosed either by clinical judgement , starting treatment empirically and continuing if found clinical improvement.Mostly TB is daignosed by ESR, CRP,Total count,chest X-ray, CSF cobweb coagulum,Mantoux test, IGg and IGm for TB bacilli or ADA testing all provide indirect support for positivity of TB , recently for cultures new media and methods have developed but few are in practice only and 7-10 days are minimumly required to get culture of TB Mycobacterium whether typical or atypical type. Mostly if Drugs are not controlling it or if Bacilli continue to grow and if not seen by different tests then it is really a serious situation as we continue costly 3-4 to 4-6 drug regime but patient have got no cure and in many cases we become hopeless , so it was an urgent need that some tests should be developed where TB bacilli is detected exactly and correctly in 2-3 days and its sensitivity to drugs is also determined as then really correct medicines will be prescribed and we shall control MDRT and XDRT which is rapidly growing with growing number of HIV and other Immunocompromised and transplanted , cancer and collagen diseased patients on immunosupression and chemotherapy .

In America, National Institute of Health (NIH) Scientists have developed an automated test that can rapidly and accurately detect tuberculosis and drug - resistant TB bacteria in patients. The finding could pave the way for earlier diagnosis and more targeted treatment of this disease. Current diagnostic tests as mentioned above have many shortcomings.Even most widely used test, called smear microscopy for AFB by Zeil Nelson Staining , misses more than half of TB cases and cannot determine whether the bacteria are drug resistant. A more sensitive test involves growing bacterial cultures. It can spot drug resistance but may take up to 6 weeks to get results. Both tests require assessment by trained staff.

Dr. David Alland of the University of Medicine and Dentistry of New Jersey collaborated with Cepheid, a diagnostics company, has develoed a test called a DNA- based test called Xpert MTB/RIF. The test detects the TB - causing bacterium Mycobacterium tuberculosis and also resistance to rifampin (RIF) is also tested, a drug mostly used in both primary in all category I,II and III as well as in drug resistant cases until patients developed Hepatitis or idiosyncracy to this drug. RIF resistance is a good indicator of multidrug resistance.NIH's National Institute of Allergy and Infectious Diseases (NIAID) has supported the development of the MTB/RIF test for more than 8 years. To use the test, a technician adds a small sample of a patient's sputum to a plastic test cartridge and loads it into the machine. The instrument then automatically performs a series of steps that ultimately leads to an analysis of DNA from bacteria in the sample. A computerized printout reports the presence of TB bacteria and whether or not the bacteria are resistant to RIF

As described in the September 1, 2010, issue of the New England Journal of Medicine, the researchers assessed the performance of the new automated test on 1,730 patients with suspected TB in 4 countries. Each patient provided 3 sputum specimens. The samples were assessed by MTB/RIF and by conventional smear microscopy and bacterial culture tests. The new automated test successfully identified 98% of all confirmed TB cases and 98% of patients with RIF- resistant bacteria in less than 2 hours. In addition, a single MTB/RIF analysis detected TB in over 72% of patients who did not appear to have TB according to smear microscopy but who were later found to have TB in culture tests. When the automated test was repeated, the sensitivity increased by about 13%. When the test was run a third time, it detected about 90% of TB cases that were missed by smear microscopy.The scientists note that the MTB/RIF test makes it possible to detect TB and drug resistance in a single clinic visit and perhaps begin treatment immediately, a significant advantage in developing countries. "The test also indicates rapidly whether difficult- to - treat drug- resistant forms are present," says Alland. "This is a major advance over other rapid TB detection methods, which are complex, labor- intensive, and technically challenging."

Therefore,if later on such tests and machine becomes cost effective and easily procurable in our country or Developing countries or Africa where HIV is widely spread , it will be a test of time and most trusted test and gradually scientist will determine drug resistance to INH,Ethambutol,Pyrizinamide etc.


Refered by: DR. D. R. Nakipuria

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