IiSGM leads a study using genomic analysis to better understand how tuberculosis is transmitted
Open the door to more precise and personalized control strategies
The Gregorio Marañón Health Research Institute, through its Clinical Microbiology and Infectious Diseases Research Group, has led an international study applying advanced genomic analysis to better understand how tuberculosis is transmitted and why some cases appear clustered within the same chains of transmission. According to the researchers, this type of more detailed analysis provides a better understanding of the dynamics of the disease, paving the way for more precise and personalised control strategies.
This is one of the most comprehensive analyses carried out to date in Spain on the application of genomic epidemiology to the monitoring of infectious diseases. Its results reinforce the potential of these tools to improve the detection, control and prevention of tuberculosis.
The research, published in the scientific journal Eurosurveillance, the official journal of the European Centre for Infectious Diseases (ECDC), analysed nearly 2,000 culture-positive tuberculosis cases diagnosed over a 20-year period in the province of Almería, one of the areas of Spain where the most comprehensive epidemiological studies on this disease have been conducted.
To study how the different cases are related to one another, the researchers carried out molecular analysis at Hospital Universitario Torrecárdenas, with the support of the University of Almería, of the bacterium that caused the disease in each of these individuals and subsequently sequenced their complete genomes at the Microbial Genomics Laboratory of Hospital Gregorio Marañón. Through this analysis, the researchers were able to compare the microorganism's genetic variants with great precision and determine whether several patients were part of the same chain of transmission.
Precise analysis of chains of transmission
The study went beyond conventional genomic analysis, taking a more evolutionary approach and focusing on the emergence of genomic variants along chains of transmission. In addition, this refined genomic analysis was combined with equally refined clinical and epidemiological research , coordinated by epidemiological surveillance professionals from the various areas of the province of Almería, to reconstruct in greater detail how these chains of transmission developed over time.
"We are applying sequencing not only to identify cases transmitting tuberculosis, but also to carry out a highly accurate analysis of the relationship between each case and the previous cases in that chain of transmission," explains Darío García de Viedma, a researcher at the Gregorio Marañón Health Research Institute and one of the study's leads, together with Laura Pérez García. "By combining this information, we can better understand why some chains remain active, distinguish recent infections from old infections that reactivate years later, or detect delays in diagnosis," he adds.
The results show that only around one third of the groups that continue to grow are actually due to recent transmission. In many of the new cases added to these groups, the explanation may lie in the reactivation of infections acquired years earlier, long periods without diagnosis, or stages of the disease with barely noticeable symptoms. Therefore, the study concludes that not all cases that appear to be related are the result of recent infections, which could help improve disease surveillance and control strategies.
"This refinement of genomic analysis, which is not routinely applied in tuberculosis, allows us to design control interventions adapted to the nature of each case," adds García de Viedma, who is also a member of the Centre for Biomedical Research Network on Respiratory Diseases (CIBERES). "In this way, we can better target public health measures and improve disease surveillance."
