TUBERCULOSIS is hardly a new scourge. Lately, however, the disease—caused by bacteria that travel through air and attack the lungs—has become much harder to fight. Drugs that once quashed the bugs have become, if not completely useless, then only sporadically effective. A big new study, published in the Lancet, provides a global portrait of the bacteria’s resilience.
Tracy Dalton of America’s Centres for Disease Control and Prevention (CDC) led the far-flung research team, working with scientists from Peru, the Philippines, South Korea, Russia, Estonia, Latvia, South Africa and Thailand. Other studies have reported a rise in bacteria resistant to drugs. Use of back-up drugs, in turn, has bred resistance to the back-ups. Dr Dalton set out to tally where these bacteria were most prevalent and just how resistant they had become.
The findings are not encouraging. Dr Dalton and her colleagues examined patients from eight countries. Researchers collected sputum, the polite word for coughed-up mucus, then shipped it to the CDC to test the bacteria’s response to drugs.
In total, 43.7% of the 1,278 patients did not respond to at least one so-called second-line drug, used when the most popular medicines fail. The results varied widely from one country to another. In Thailand the figure was 33.3%; in Latvia a staggering 62% of samples showed resistance.
Dr Dalton also looked at extensively drug-resistant, or XDR, tuberculosis, which is almost untreatable, failing to respond to back-ups to the back-ups. Researchers observed XDR tuberculosis in 6.7% of patients, ranging from 0.8% in the Philippines to 15.2% in South Korea. Worryingly (but unsurprisingly), resistance was higher in those countries which had had access to second-line drugs for a longer period of time. This suggests that, unchecked, it is only a matter of time before XDR tuberculosis arises in countries where second-line drugs arrived more recently, such as Thailand and the Philippines.
On an individual basis, the best predictor of whether drugs would work in a patient was whether he had been treated for tuberculosis before. Other risks included factors such as unemployment and alcohol use. This may be because these patients would be less likely to adhere to a strict medical regimen, giving bacteria a chance to evolve around existing drugs. The study, however troubling, offers only an incomplete picture. India and China, home to the largest number of tuberculosis cases, are not included.
via Babbage http://www.economist.com/blogs/babbage/2012/08/tuberculosis?fsrc=gn_ep
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