A new form of genetic testing of the bacteria that causes tuberculosis can provide better information on TB transmission and also trace TB outbreaks more accurately than the current standard test, according to a study from Germany published in this week’s PLOS Medicine.
A team of researchers led by Stefan Niemann from Forschungszentrum Borstel, Molecular Mycobacteriology, compared the results of the two types of tests on 86 M. tuberculosis isolates from a TB outbreak in the German states of Hamburg and Schleswig-Holstein between 1997 and 2010, in which 2301 people were diseased in the study period.
They found that the newer whole genome sequencing test provided more accurate information on clustering and longitudinal spread of the pathogen than the standard genotyping test. Importantly, whole genome sequencing revealed that first outbreak isolates were falsely clustered by classical genotyping and do not belong to one recent transmission chain.
By using whole genome sequencing, the authors estimated that the genetic material of M. tuberculosis evolved at a rate at 0.4 mutations per genome per year, suggesting that the bacterium grows in its natural host with a doubling time of 22 hours, or 400 generations per year. This finding about the evolution of M. tuberculosis indicates how information from whole genome sequencing can be used to help trace future outbreaks.
The researchers note that as the costs of whole genome sequencing are declining and the availability of “bench top” genome sequencers is increasing, this test could soon become the new standard for identifying transmission patterns and rates of infectious disease outbreaks.
“Our study demonstrates that whole genome sequencing-based typing provides epidemiologically relevant resolution of large, longitudinal [Mycobacterium tuberculosis] outbreaks much more efficiently than classical genotyping,” stated the authors.”
Tuberculosis remains a major public health problem, particularly in low- and middle-income countries. In 2011, an estimated 8.7 million people developed tuberculosis globally, and 1.4 million people died from the disease. Tuberculosis is second only to HIV/AIDS in terms of global deaths from a single infectious agent.
Read more on this research at PLOS Medicine: Whole Genome Sequencing versus Traditional Genotyping for Investigation of a Mycobacterium tuberculosis Outbreak.
