DNA sequencing tracks spread of drug-resistant TB

DNA sequencing traces drug-resistant TB
DNA sequencing traces drug-resistant TB | Courtesy of
DNA sequencing has been used for the first time to determine the spread of multidrug-resistant tuberculosis (TB) among TB patients residing in the U.K., researchers said Monday.

Some strains of TB are resistant to drugs, creating multidrug-resistant TB (MDR). This strain has become more prevalent in the U.K.. There were 28 cases reported in 2000. The number of cases increased to 81 in 2012.

With the genetic tracing between people with TB, researchers are able to more accurately track the source of TB infections.

Using these genetic analyses, the researchers found that a 44-year-old man initially contracted the drug-resistant form of TB from a health care worker who had been working in South Africa. Both individuals were hospitalized at the same medical ward four years before the 44-year-old man contracted the disease and died in 2012.

TB is transmitted through the air exchanged from person to person. TB bacteria can live in a human’s lungs for extended periods before symptoms surface. The time period before the symptoms arise is called latent infection.

"Multidrug resistant TB is a real problem in the U.K.," Imperial College London Department of Medicine Senior Clinical Lecturer in Infectious Diseases Graham Cooke said. Cooke was lead author of the TB study. "It takes a lot of time, effort and resources to treat, and treatment is less successful. 

"Genetic sequencing enabled us to establish beyond reasonable doubt that a patient who died of multidrug-resistant TB caught the infection from another patient at a hospital in the U.K.," Cooke said. "Genome sequencing of pathogens is becoming part of routine practice for establishing transmission patterns for TB and other infectious diseases. This sort of analysis will help to improve our understanding of how diseases spread and identify more effective ways to stop them. 

"In this case, the infection was traced to a health care worker,” Cooke said. “At a time when Ebola is in the news, this reminds us that health care workers are vulnerable to many infections and, if not diagnosed, have a high risk of passing them on."

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Imperial College London

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