English researchers have developed a blood test capable of identifying tuberculosis even in patients who had not yet contracted the active form of the disease.
Tuberculosis is an infectious bacterial disease that primarily affects the lungs. In 2016, 1.7 million people died, making it the deadliest infectious disease in the world. Because although there is a vaccine to prevent it and it is treatable with antibiotics, the most affected populations are also the most disadvantaged and therefore those who have the least access to care.
A quarter of the world’s population is infected with tuberculosis.
In all, about a quarter of the world’s population carries the disease. Most often, this has no impact on health. But in 5-10% of cases, tuberculosis wakes up. However, a new study published in the medical journal Clinical Infectious Disease could greatly facilitate diagnosis. British researchers have succeeded in developing a potential new blood test capable of identifying tuberculosis in patients and even in patients at risk.
During their study, researchers from Leicester and Nottingham followed 66 people and separated them into four groups. The first had active pulmonary tuberculosis, the second suffered from a latent form of the disease, the third was suspected of having it and the last consisted of healthy individuals.
In order to identify the presence of the bacterium that causes tuberculosis, they gave the participants their Actiphage blood test twice, a year apart. Result: Actiphage was able to identify 73% of patients who had already been diagnosed. No participant in the healthy control group tested positive and no patient with latent tuberculosis who tested negative subsequently developed an active form of the disease. In contrast, two of the three participants with latent infection who tested positive developed the disease more than six months later. Thus, Actiphage could make it possible to identify people at risk, welcome the researchers.
A specific bacteriophage to identify the Mycobacterium tuberculosis
“The most common symptoms of TB affect the lungs and from there the disease can spread to others through coughing and sneezing. While there is a lack of tools to diagnose people unable to perform sputum (the expulsion by the mouth, during the effort of coughing, of pathological products from the broncho-pulmonary and upper airways, NLDR), like children for example, the diagnosis is delayed, which promotes the spread of the disease,” says Dr. Pranabashis Haldar, lead author of the study. Remember, however, that only the pulmonary forms of tuberculosis can be contagious.
Furthermore, the detection of Mycobacterium tuberculosis (MBT), the bacterium causing the disease is limited because it grows very slowly, which makes traditional cultivation methods ineffective. However, Actiphage uses a specific bacteriophage capable of efficiently releasing the bacteria’s DNA and identifying it in just six hours.
“Data from our human study provide evidence that after infection, MBT circulates in the blood at levels that were previously undetectable and that the immune system may fail to effectively contain the bacteria in the lungs,” says Dr. Catherine Reese, co-author of the study.
Since 2007, the vaccine is no longer compulsory in France
Thus, “our observations give a better understanding of how human tuberculosis develops”, welcome the researchers who hope to one day be able to market their test. While larger-scale studies are yet to take place, “this new test offers the potential to target those at risk and treat them as early as possible.” “It’s very exciting,” conclude the researchers.
In France, the health authorities strongly recommend vaccination against tuberculosis, especially in infants, who are particularly exposed to the bacillus. However, this has not been compulsory since 2007. And today, if the incidence of the disease is low in France, it has not completely disappeared. In 2015, there were still 4,741 new cases reported.
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