News 2024

Mycobacterium tuberculosis, the causative agent of tuberculosis, is transmitted from person to person via droplets. Patients suffering from pulmonary tuberculosis excrete the pathogens when coughing and sneezing and are inhaled by contact persons in this way. In order to prevent the spread of tuberculosis, it is not only important to isolate and treat patients immediately, but also to identify and test close contacts in the patient's environment.

Special immune tests can be used to determine whether you have already been infected with tuberculosis bacteria. These tests cannot detect the infection itself, but provide indirect information on whether immune cells have been formed in the body that are directed against tuberculosis bacteria or individual components of the tuberculosis bacteria. The most commonly used tests are the tuberculin skin test and the so-called interferon-gamma release assay (IGRAs).

If it is suspected that you have been infected as a close contact person or if an immune test is positive, preventive therapy can be initiated. This prophylactic administration of antibiotics can be very useful in preventing a disease - however, due to the duration and side effects, its use is not always advisable. It is assumed that every 4th person worldwide carries the TB pathogen without contracting the disease. Risk groups for the development of active pulmonary tuberculosis are mainly young children, immunocompromised people and people from countries where tuberculosis is common.

“Through this work, we wanted to obtain robust data on which individuals benefit most from preventive tuberculosis treatment and whether this benefit differs in countries with high and low exposure of the population to tuberculosis bacteria,” explains Prof. Christoph Lange, senior author of the study and Medical Director at the Research Center Borstel, Leibniz Lung Center.

In order to investigate the effectiveness of preventive tuberculosis treatment in exposed persons of different ages and Mycobacterium tuberculosis infection status, taking into account the tuberculosis burden in the environment, the research team led by Dr. Leonardo Martinez and Professor C. Robert Horsburgh from Boston University in the USA, Professor Christoph Lange and Leibniz Chair Professor Anna Mandalakas from Baylor College of Medicine in Houston, USA, examined publications from the last 20 years and included a total of 430,000 persons exposed to tuberculosis in this study. The study also took into account how many contact persons need to be treated (number needed to treat (NNT)) in order to prevent the disease. The study has now been published in the renowned journal Lancet Respiratory Medicine.

 “The result is clear!” concludes Christoph Lange. “In countries with a low incidence, you have to test and should only treat those contact persons who have a positive test result. In recent years, we have been able to show that blood tests are a better indicator of the risk of tuberculosis than skin tests. Neither test is particularly good at predicting the future risk of developing tuberculosis. The situation is different in high-incidence countries. There it makes no difference whether the test result - whether blood test or skin test - is positive or not, all contact persons should be treated.”

“As preventive antibiotic therapy is very effective, it should be used much more, especially in high-incidence countries,” says Professor Lange. “Until we have a better vaccine to protect against tuberculosis, preventive antibiotic treatment of contact persons is one of the most effective measures to prevent the spread of tuberculosis.”

Publication:

Martinez, L., Seddon, J. A., Horsburgh, C. R., Lange, C., Mandalakas, A. M. (2024). Effectiveness of preventive treatment among different age groups and Mycobacterium tuberculosis infection status: a systematic review and individual-participant data meta-analysis of contact tracing studies. The Lancet Respiratory Medicine. https://doi.org/10.1016/S2213-2600(24)00083-3

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