In this video, we're going to discuss virulence. And so the term virulence can be defined as the degree of pathogenicity of an organism, or in other words, virulence is the degree of disease production of an organism, how well it can cause disease. And so an organism with very high pathogenicity is going to be more virulent, and that means, of course, that it is going to be more likely to be able to cause an infection and more likely to cause disease. Whereas, of course, an organism with a lower pathogenicity would be less virulent and would be less likely to cause an infection and less likely to cause disease.
Now the virulence factors can be defined as the specific traits that an organism has that allows it to cause disease, or the specific factors that allow it to become virulent. For example, a virulence factor could be a specific gene that the organism has that allows for toxin production, and this specific gene could be the reason for its virulence or the reason for its pathogenicity. And so if we take a look at our image down below, notice on the left hand side over here, we're showing you some diseased lungs over here that have the bacterium Mycobacterium tuberculosis, which is going to be the cause of tuberculosis or TB and leads to symptom signs and symptoms such as chronic cough and coughing up blood, chest pain, weakness and fatigue, weight loss, weight loss and loss of appetite, fever and chills, and night sweats. And so Mycobacterium tuberculosis would be considered a pathogen that has a high degree of virulence.
Now over here on the right hand side, we're showing you a healthy gut. And zooming into the healthy gut, what you'll find is a bacterium called Bifidobacterium animalis, and this bacterium is part of the healthy gut microbiome. And so it is actually a non virulent microbe, and that means that it has a very low degree of virulence, a low chance of causing infection and disease. And so notice that if this bacteria is in excess in the gut, it would only cause things like stomach gas and bloating, and rarely it would cause fever and chills. But it is not going to cause nearly as many signs and symptoms of disease as a virulent pathogen.
And so this here concludes our discussion on virulence, and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.
