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Mycobacterium Tuberculosis Vs. Avium Complex And More
Mycobacterium tuberculosis (M. Tuberculosis) is a bacterium that causes tuberculosis (TB) in humans. TB is a disease that primarily affects the lungs, although it can attack other parts of the body. It spreads much like a cold or the flu — through the expelled airborne droplets from a person with infectious TB.
When inhaled, the bacterium can settle in the lungs, where it begins to grow. If not treated, it can spread to areas such as the kidneys, spine, and brain. It can be life-threatening.
According to the Centers for Disease Control and Prevention (CDC), more than 9,000 new cases of TB were reported in the United States in 2017.
Learn What Mycobacterium Bovis Is, What It Causes, And More - WebMD
Do you work closely with domestic animals? Have you recently consumed undercooked meat from a wild animal? If so, you may have been exposed to Mycobacterium bovis, a foodborne pathogen.
Let's dive into what Mycobacterium bovis is, its symptoms, and how it's transmitted, diagnosed, and treated. Then, we'll look at ways to prevent contamination.
Mycobacterium bovis (M. Bovis) is a bacterium belonging to the Mycobacterium tuberculosis group that causes bovine tuberculous disease in humans and animals. Most human tuberculosis (TB) cases come from Mycobacterium tuberculosis (M. Tuberculosis). M. Bovis also has an extensive range of hosts that can carry the bacteria and develop mycobacterium bovis tuberculosis.
Those affected may include:
M. Bovis can also cause asymptomatic TB, which may not show any symptoms. This is called a "latent TB infection" (LTBI). People with LTBI cannot spread the disease and usually feel no symptoms. Over time, however, the latent form can turn into symptomatic TB.
TB can be transmitted through the air or infected food and milk. People can also become infected after receiving a cut from an infected animal or another type of open wound.
Some people who are infected with Mycobacterium bovis never display any symptoms. You may also have the infection and simply not notice any symptoms right away. Around four weeks in, though, some possible Mycobacterium bovis symptoms can include the following:
If the disease goes untreated for too long, you can die. However, this is a rare occurrence, as people receive successful treatment most of the time. Alternatively, the condition can go unnoticed, remaining dormant for an entire lifetime.
M. Tuberculosis and M. Bovine cause similar symptoms. Humans, other primates, and guinea pigs are highly susceptible to M. Tuberculosis. Cattle, rabbits, and cats are more susceptible to M. Bovis. Pigs and dogs are vulnerable to both strains. When humans contract M. Tuberculosis, it is almost always spread from another human rather than an animal.
In terms of their respective symptoms, M. Bovis is more often an intestinal disease, whereas M. Tuberculosis more commonly affects the lungs.
Mycobacterium bovis is a zoonotic disease that infects humans and animals and transmits between them. You can breathe in the pathogen, or the condition can be transferred via infected milk or food.
This risk of transmission can be significantly reduced by pasteurization: the process of heating milk to a temperature high enough to kill bacteria. M. Bovis was actually one of the diseases that motivated the original implementation of the pasteurization process in the early 1900s because small children were contracting the disease from drinking contaminated milk. M. Bovis infections caused approximately 5–30% of all human TB cases in the United States and the United Kingdom during that time.
Even today, people working on farms or in close contact with animals are at a greater risk of infection. A recent study found that slaughterhouse workers, livestock farmers, and butchers had the most significant risk of becoming infected by M. Bovis.
Also, in places where pasteurization is not mandatory, the risk of drinking contaminated milk is significant. TB developing from mycobacterium bovis transmission to humans has become quite rare, though. Today, less than 2% of reported human tuberculosis cases come from M. Bovis.
A TB blood test and a TB skin test are available to determine whether you have tuberculosis, and they are broadly recommended to a subset of people who are more likely to develop symptomatic tuberculosis. These high-risk individuals include:
M. Bovis is often treated the same way as M. Tuberculosis because health care professionals often don't know which one you have. Mycobacterium bovis treatment involves the use of a few antibiotics together, often including rifampicin, isoniazid, and ethambutol.
The M. Bovis strain is resistant to the antibiotic pyrazinamide, one of the antibiotic medications used to treat M. Tuberculosis.
The most common way to become infected with M. Bovis is by drinking unpasteurized milk, so the best preventative measure is to avoid doing so.
Additonally, if you hunt or work closely with animals, you should wear protective equipment to reduce your chances of contracting this disease. If you believe you have been exposed to M. Bovis, seek medical attention as soon as possible.
Remodeling The Immune System To Fight Tuberculosis
Tuberculosis, caused by the bacterium Mycobacterium tuberculosis (Mtb) kills upwards of 1.6 million people a year, making it one of the leading causes of death by an infectious agent worldwide -- and that number is only growing larger. How, exactly, Mtb evades the immune system isn't yet known, but a collaborative team of researchers from the University of Massachusetts Amherst and Seattle Children's Research Institute recently discovered something surprising: prior exposure to a genus of bacteria called Mycobacterium seems to remodel the first-line defenders in the body's immune system. Furthermore, how those cells are remodeled depends on exactly how the body is exposed. These results, published recently in PLOS Pathogens, suggest that a more integrated treatment approach that targets all aspects of the immune response could be a more effective strategy in the fight against tuberculosis.
"We breathe in thousands of liters of air every day," says Alissa Rothchild, assistant professor in the Veterinary and Animal Sciences Department at UMass Amherst and the paper's senior author. "This essential process makes us incredibly vulnerable to inhalation of all sorts of potentially infectious pathogens that our immune systems have to respond to."
Systems, plural. When we think of immunity, we typically think of the adaptive immune system, which is when prior exposure to a pathogen -- say, a weakened version of chickenpox -- teaches the immune system what to guard against. Vaccination is the most common tool that we use to teach our adaptive immune systems what to look out for.
While the adaptive immune system is the major focus of most vaccine research (think protective antibodies induced by COVID-19 vaccines), it is not the body's first responder -- that would be the innate immune system and its ranks of macrophages. The macrophages are the first-line defenders in the tissues that recognize and destroy pathogens and also call for backup. One way they do this by turning on different inflammatory programs that can change the tissue environment.
In the case of the lungs, these macrophages are called alveolar macrophages (AMs). They live in the lung's alveoli, the tiny air sacs where oxygen passes into the bloodstream -- but, as Rothchild has shown in a previous paper, AMs don't mount a robust immune response when they're initially infected by Mtb. This lack of response seems to be a chink in the body's armor that Mtb exploits to such devastating effect. "Mtb takes advantage of the immune response," says Rothchild, "and when they infect an AM, they can replicate inside of it for a week or longer. They effectively turn the AM into a Trojan Horse in which the bacteria can hide from the body's defenses."
"But what if we could change this first step in the chain of infection?" Rothchild continues. "What if the AMs responded more effectively to Mtb? How could we change the body's innate immune response? Studies over the last 10 years or so have demonstrated that the innate immune system is capable of undergoing long-term changes, but we are only beginning to understand the underlying mechanisms behind them."
To test conditions where the innate immune response might be remodeled, Dat Mai, a research associate at Seattle Children's Research Instituteand the first author of the paper, Rothchild and their colleagues designed an experiment using two different mouse models. The first model used the BCG vaccination, one of the world's most widely distributed vaccines and the only vaccine used for tuberculosis. In the second model, the researchers induced a contained Mtb infection, which they previously showed protects against subsequent infections in a form of concomitant immunity.
Weeks after exposure, the researchers challenged the mice with aerosolized Mtb and infected macrophages were taken from each mouse model for RNA sequencing. There were striking differences in the RNA from each set of models.
While both sets of AMs showed a stronger pro-inflammatory response to Mtb than AMs from unexposed mice, the BCG-vaccinated AMs strongly turned on one type of inflammatory program, driven by interferons, while the AMs from the contained Mtb infection turned on a qualitatively different inflammatory program. Other experiments showed that the different exposure scenarios changed the AMs themselves, and that some of these changes seem to be dependent on the greater lung environment.
"What this tells us," says Rothchild, "is that there's a great deal of plasticity in the macrophage response, and that there's potential to therapeutically harness this plasticity so that we can remodel the innate immune system to fight tuberculosis."
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