Tuberculosis: Improved genetic test to improve surveillance
Tuberculosis is still one of the most dangerous diseases worldwide. Every year, millions of people contract the bacterial infectious disease, many do not survive. Using the genetic material of the bacteria causing tuberculosis, researchers want to better monitor outbreaks in future and identify antibiotic-resistant tuberculosis bacteria. In its “Global Tuberculosis Report 2012”, the World Health Organization (WHO) estimated the number of new tuberculosis cases for 2011 at 8.7 million cases worldwide. According to the WHO, 1.4 million people died of tuberculosis in 2011.
A team of experts from public healthcare institutions, research institutes and universities in Germany and France around Stefan Niemann from the Borstel Research Center at the Leibniz Center for Medicine and Biosciences in Borstel has evaluated the results of two different genetic tests for Mycobacterium tuberculosis isolates and their results in the specialist magazine "PLoS Medicine" released. Overall, the data of 2,301 patients from Schleswig-Holstein and Hamburg were recorded over a period of around thirteen years (1997 to 2010), according to Stefan Niemann and colleagues in the journal.
During the population-based epidemiological surveillance, a larger outbreak was identified with that with classic strain typing, which was initially attributed to the strain of the Haarlem line of the Mycobacterium tuberculosis. However, the newer genome-wide sequencing methods would have given clearly more precise results and showed that it is actually a "Hamburg clone" of the bacterial strain, which probably developed between 1993 and 1997. The researchers will be able to use the novel genetic tests to better control the development and distribution of tuberculosis bacteria in the future.
Monitor tuberculosis infection chains with new genetic tests
Previous genetic tests that are used to analyze tuberculosis bacteria, according to the scientists, only record a small proportion of the genome, which significantly reduces the precision. Here, the complete sequencing of the bacterial genes offers clear advantages. This way, a possible outbreak can be monitored much better. Because the exact genetic assignment makes it easier to relate the diseases to each other. So far, after reporting a tuberculosis patient to the health authorities in their environment, "after further cases and possible infection chains," Niemann explained. This will remain indispensable in the future, but the exact genetic assignment can make identification of the infection chains much easier.
Detect antibiotic-resistant tuberculosis bacteria
In addition, "the genome-based investigation is of great importance when it comes to detecting and spreading the tuberculosis bacteria that have become resistant to several antibiotics," explained Stefan Niemann. To date, tuberculosis is usually treated with antibiotics, with a combination of different preparations usually being used over a period of around six months. However, since the spread of multidrug-resistant bacteria has increased significantly in recent years, tuberculosis therapy with standard drugs is proving to be an increasingly difficult task. The pathogens hardly respond to the common antibiotics and the treatment can be delayed massively. To monitor the spread of multidrug-resistant tuberculosis bacteria, "the new genetic tests are much more suitable than conventional genetic tests," the researchers report.
Tuberculosis the deadliest infectious disease worldwide
While tuberculosis is a rather rare disease in Germany (the Robert Koch Institute reported 4,268 diseases in 2012), less developed countries in particular often have to deal with regular epidemics. Although global strategies to reduce tuberculosis infections have had an impact in recent years, tuberculosis (also known as consumption) remains the world's deadliest infectious disease, according to the WHO. In fact, only a fraction of those infected fall ill. People with a weakened immune system are at particular risk here, for example due to an HIV infection.
Recognize signs of tuberculosis
The course of the disease of tuberculosis is generally divided into several stages. For example, a distinction is made between primary tuberculosis and secondary tuberculosis. The typical signs of tuberculosis include constant mild cough, fatigue, loss of appetite and a corresponding weight loss, mild fever and swollen lymph nodes in the initial stages. If the pathogens can spread through the bloodstream in the patient's organism, there is a particularly severe course of the disease, the so-called miliary tuberculosis. In the worst case, this can lead to life-threatening meningitis (meningitis). People with extremely weak immune systems may also experience potentially fatal blood poisoning (sepsis) as a result of the illness. Improving the monitoring of possible tuberculosis outbreaks with the help of new genetic tests could make a significant contribution to the prevention of consumption. (fp)