Mumbai’s XXtreme TB is neither new nor sudden

Mumbai has been in a state of panic for the last two weeks after doctors at Hinduja Hospital reported the first cases from India of Extremely Drug Resistant TB (XXDR), which is immune to all first-line and second-line drugs used in the disease’s treatment. The panic stems from the idea that we are facing a new kind of bacteria and the possibility that it may spread among a large section of people in the city.

It’s worth pointing out, therefore, that the earliest reported case of XXDR TB was way back in 2003 in Italy, according to a 2007 article in medical journal, Eurosurvelliance. In this article, GB Migliori, director, WHO Collaborating Centre for TB and Lung Diseases, discussed the cases of two patients who initially had a less severe form of TB but it developed into XXDR TB due to mismanagement of the disease at the earlier stage. One of them underwent treatment for five years, while the other was treated for almost eight years. Drug susceptibility tests (DST) were performed on both patients, which indicated that the TB was resistant to all known anti-TB activity, wrote Migliori. “Both (women) died in 2003, before 50 years of age, after a long, unsuccessful treatment with all available drugs without achieving bacteriological conversion.”

In 2003, the only known forms of the disease were the primary TB and multi-drug resistant TB (MDR TB). When the bacteria developed resistance to the first line of drugs for primary TB, patients with MDR TB would then be treated with second-line drugs.   

However, doctors started noticing that some MDR TB patients too were showing resistance to some of the second-line drugs. “In 2006, WHO officials met in Geneva to define XDR TB (extensively drug-resistant TB). In the same meeting, XXDR TB too was discussed, and the term was accepted unofficially,” said Migliori, when contacted by DNA.

According to Migliori, it is difficult to identify XXDR TB, since the patient has to be tested against all available drugs. This is expensive and “the test results are open to interpretation. Moreover, there are few labs in the world who can conduct such tests,” he said. What this implies is that over the years many XXDR cases may not have been documented; so it may be fallacious to think that there has been a sudden emergence or spike in XXDR TB.

Doctors in India agree. “DST (drug susceptibility testing) for all the drugs is costly and not effective for treatment. So the testing is done only for the primary drugs. DST for other drugs is also dubious right now. The same test carried out by different labs yields different results, and the technology is non-standardised,” said SK Jindal, chairman of the Expert Advisory Committee on Management of Tuberculosis.

Only three labs in India are accredited to carry out DST for all available TB drugs, which is needed to confirm XXDR TB. Other labs can only diagnose MDR TB and XDR TB.

Bacteria strains are rarely tested for sensitivity against all drugs, said experts. “We can only classify a strain as XXDR if we can get it tested from an accredited lab, of which there are very few in India. Moreover, these labs only accept samples from patients who are being treated via the Revised National Tuberculosis Control programme, and not from private parties,” said KC Mohanty, HOD, Chest Medicine, KJ Somaiya Hospital.

While Hinduja tested and found 12 XXDR TB cases, Jindal concedes that there may be several others which have gone unreported. With the government now moving to accredit more laboratories to carry out DST for all drugs, you can expect more XXDR cases to surface.

So, then, are we in the middle of an XXDR TB outbreak? “No,” says Jindal, “TB is not as virulent as the H1N1 virus (swine flu). It spreads mostly when there is close contact with the patient. And XXDR TB is no different.”