TB bacteria can survive
in tissues using carbon monoxide
A disease that has been present for millennia
Today, many life-threatening infectious diseases have been either eradicated or are possible to avoid with the use of vaccines. There are of course exceptions, one of which is tuberculosis (TB); a disease that has been present for millennia. In the early days the disease was also denoted as consumption or “wasting away disease”, due to that those who were affected tended to lose significant weight. TB was a rampant disease in particular during the 17th, 18th, and 19th centuries, and effective treatments were absent. So-called sanatoriums were established in mountainous areas as it was thought that sunshine and the fresh air of the mountains could help to control the disease. It is said that it was even more common for people to head to the Rocky Mountains in Colorado in search of a cure for TB than in search of gold.
A leading cause of death
To this day, TB is one of the worldwide leading causes of death from infectious disease and it is estimated that approximately 25% of the world’s population carries the bacterium that causes it. When the infection is dormant, it tends to not exhibit any symptoms. However, once the individual’s immune system becomes compromised, the infection can advance into unabridged TB. There are different forms of TB, which determines the treatment form offered. While treatment for TB can take months, the prognosis for patients today is good, under the presumption that the form has been correctly diagnosed. This is not always a given; TB has been termed “the great imitator” as it’s symptoms closely resemble those of a multitude of diseases. Symptoms include but are not limited to chronic cough, chest pain, fever, night sweats, and appetite loss. However, as mentioned, in some individuals the infection lies dormant and may never come to express any symptoms.
Carbon Monoxide as a source of energy
What is it then that allows the TB bacteria to stay present in the system in the wait for an immunocompromised moment? The results of a new study recently published in the ISME Journal point towards that mycobacteria – the group of bacteria that cause TB as well as leprosy and Buruli ulcer – can utilize carbon monoxide as a source of energy when no other nutrients are available. The study, which was conducted by a team of microbiologists under the lead of Professor Chris Greening at the School of Biological Sciences at Monash University, shows that the consumption of carbon monoxide allows mycobacteria to survive in human tissue for long periods of time. While it has been known from before that TB bacteria can use carbon monoxide, it was unclear for what purpose until now.
Furthermore, the study showed that the mycobacteria use an enzyme called carbon monoxide dehydrogenase to scavenge the energy contained in the gas. While the energy that is provided upon breaking the gas down into its fundamental components is not enough for the bacteria to grow, it does provide sufficient energy for them to persist. Looking ahead, this new discovery of the survival mechanisms of these kinds of bacteria can be used in the development of new strategies to combat infectious diseases such as TB.
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