Rwandan doctor discovers rare lineage of a TB causing bacteria

Dr Jean-Claude Semuto led a team of six Rwandan scientists from Rwanda Biomedical Center who identified a new type of tuberculosis causative agent. Courtesy

For the first time in the history of Rwanda, Dr Jean-Claude Semuto, supported by a team of six Rwandan scientists from Rwanda Biomedical Center, has identified a new type of tuberculosis causative agent.

The new tuberculosis bacterial strains belong to a new lineage dubbed Mycobacterium tuberculosis complex, the same family of human-adapted pathogen causing the global tuberculosis pandemic.

Sunday Magazine’s Bertrand Byishimo talked Dr Semuto to find out more about his discovery and findings.

You discovered a new lineage of a bacteria causing TB. How did the idea come about?

We realised it in December 2017, after DNA sequencing of a sample collected from patients diagnosed with multidrug-resistant tuberculosis from Rukozo sector in Rulindo District. The patient was diagnosed at a health center and was referred to start treatment at Kibagabaga Hospital.

As part of the ongoing study, we (at RBC) enrolled this patient and requested for more samples for further testing. That is when we went further, characterized and analyzed the sample until when we came up with our findings.

Had this type of bacteria been discovered anywhere before?

It was once discovered in Uganda. Additionally, our patient who lived in Rulindo District is said to have traveled to Uganda many times. He might even have gotten the bacteria there (you never know) because it was once found there. This DNA sequence from Uganda had been found, sent and sequenced in a wrong way in Switzerland.

Apart from that, these cases are very special and very rare. We screened the world data collection of typing pattern (spoligotype), also in the sequences we have done so far and inspected in other neighbouring countries for available sequence data, but no additional strain of such type was observed except the above mentioned in Uganda.

Is the discovery in line with the TB pandemic in the modern world?

Of course. Tuberculosis remains one of the oldest causes of death today. The World Health Organisation reports a total of 1.5 million people who died from TB in 2018 (including 251,000 people with HIV). Worldwide, TB is one of the top 10 causes of death and the leading cause from a single infectious agent (above HIV/AIDS).

How does Swiss Tropical and Public Health get involved?

In parallel, a team of researchers from Swiss Tropical and Public Health had identified a genome in public repository with similar characteristics to Rwanda’s, both with unusual spoligotype.

That was a genome submitted from Uganda which was previously misclassified as a well-known TB causative agent in cows, yet having such unique and special characteristics.

Given the fact that both strains belong to a single new lineage of Mycobacterium tuberculosis complex, we decided to collaborate documenting such unusual and very special type of TB strains to find out what causes it.

Is this your first time publishing this?

Our findings were presented in June to a conference of The European Society of Mycobacteriology Congress (ESM). They were convinced that it is a new lineage.

Now, we are finalising and documenting all scientific facts about this research, the reason why we chose to publish it at this time.

What impact do you expect from this research?

This research intends to validate newly developed, rapid and more accurate diagnostic tools for Tuberculosis because it is medically unexplainable to look for a cure without knowing the cause.

The medicaments we were giving to the patient were not helping anyway because he had a new species of the bacteria. So, as long as we have discovered the new cause, it will simplify the discovery of a new treatment.

Is this research solely a product of RBC work or you have some collaborators?

We carried out this research together with international researchers from the Institute of Tropical Medicine (Antwerp, Belgium), Geno Screen (Lille, France), Swiss Tropical and Public Health Institute (Basel, Swiss). Help however, was given only in terms of combining the findings from both sides.

How can you summarize the research?

The two-year research was a long journey. It was like searching for a needle in a haystack, and then pulling the needle out with a magnet; it took us a long time to be able to fully sequence the bacteria lineage and create a full picture of it.

The discovery of tuberculosis causative agent was done by the legendary German physician Doctor Robert Koch in the 19th century.

Since that time, Scientists have always strived to make tremendous research to understand this pathogen, the diversity of this TB causative agent and what would be the best treatment.

Also there have been discoveries of eight lineages up to the time when Rwanda discovered the ninth.

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