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Tuesday, February 12, 2013

Drug-resistant tubercolosis warning!

‘Totally drug-resistant’ tuberculosis spreads in South Africa as researchers warn global outbreak would be ‘untreatable’

By National Post Staff, February 12, 2013
The world is facing outbreaks of “totally drug-resistant” tuberculosis if explosions of the bacteria in South Africa and other poorer nations are not addressed, according to a new papers published in Emerging Infectious Diseases. At this point, researchers are working to determine how the bacteria gains its invincibility, and how to isolate it.

Fears are mounting in medical communities worldwide that conventional treatments would be useless against the new disease, The Daily Mail‘s health site reports. They say doctors are warning “the world is on the brink of an outbreak of a deadly and ‘virtually untreatable’ strain of drug resistant tuberculosis unless immediate action is taken.” Fears of a repeat of the 1980s outbreak in New York City that killed 90% of the people who contracted the TB strain are being cited by those urging action in poorer countries where the disease is spiralling out of control.
Researchers writing in the U.S. Centers for Disease Control journal warned in two new studies that the further outbreaks of drug resistant tuberculosis could devastate populations and economies of developing nations, particularly in the drug-resistant strain’s ground zero regions, such as in South Africa. Recent reports from 2012, however, drive home the importance of isolating drug-resistant TB, since the disease has also been popping up increasingly in wealthier Western cities such as London, where, of course, it can attack rich and poor indiscriminately.
One study, which is monitoring the high death rates among South African patients infected with the resistant TB and HIV, noted that: “Drug-resistant tuberculosis is a critical threat to TB control and global public health.”
Another study, examining the rise of the drug-resistant strains of TB as they move through populations in South Africa found that “factors driving the increase in drug-resistant tuberculosis are not understood.” Researchers caution that, at this point, with mortality rates among some groups at more than 50%, containment is the goal, and they advocate the use of more specific screening tests so as to more easily isolate patients suffering from the virtually untreatable strain of TB. The authors of a 2008 study on HIV and TB had demonstrated that the spread of these strains was facilitated by HIV co-infection, raising particular concern for the spread of drug-resistant strains in vulnerable populations.

The current research being done in South Africa is “in order to determine whether the epidemic” of drug-resistant TB is “driven by acquisition or transmission of resistance and to describe the extent of resistance within these strains.” In other words, researchers are trying to determine the extent to which vulnerability of patients’ immune systems is contributing to the spread of the TB strains, and in what ways the transmission of drug-resistant genetic material is contributing to the strengthening of the totally drug-resistant bacteria.
Discerning between multiple drug-resistant TB and totally drug-resistant TB is key, researchers say. They noted that, “DNA data showed a significant association between the atypical Beijing genotype and mutations conferring second-line resistance” to TB treatment drugs, and that since the multiple drug-resistant TB and totally drug-resistant TB were significantly different on a genetic level, that “how to rapidly identify case-patients at risk of harboring the atypical Beijing genotype to prioritize drug susceptibility testings, ensure patient isolation and administer appropriate treatment” would be the key to preventing further spread.
They also found that it was “counterintuitive” that multiple drug-resistant TB is genetically distinct when compared to the totally resistant TB strains “because we would expect all MDR TB strains to have had an equal chance of acquiring resistance to second-line anti-TB drugs.” That, ultimately, could be good news, since they go on to note that, in addition for this development making it easier to tell the two apart among infected patients, and thereby easier to treat properly, the bacteria themselves may not be exchanging genetic information as easily as was thought, making it harder for the totally resistant TB strains to grow stronger and more virulent and likely to spread.

“An alternative explanation” for the increased resistance to drugs “would be that the atypical Beijing genotype [or totally resistant strain] acquires resistance by conferring mutations more readily than other genotypes,” researchers wrote. “The convergent evolution of seven different mutations within a single genotype is highly unlikely.”

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