Pathogenesis is a word used to describe the mechanism by which a disease develops, progresses, and persists (or resolves).
The disease-causing mycoplasmas possess the ability to:
- adhere to, and
- cause local cell injury.
(This method of invading human cells is what allows disease to develop.)
Specifically, immune evasion occurs when the bacteria that reside extracellularly (under normal conditions) attach to ciliated and nonciliated epithelial cells. Intracellular invasion has a chance to take place.
Example
In the case of Mycoplasma pneumoniae, the most widely studied of these bacteria, a specialized attachment organelle working alongside a specific adhesion protein (called P1) begins the process of pathogenesis. The attachment association prevents the host from utilizing its mucociliary mechanisms to clear the bacterium from the lung. Chronic inflammation and cytotoxicity (hydrogen peroxide, acting as a hemolysin) initiate a cascade that accomplishes this task.
As mentioned previously, normally colonizing mycoplasmas isolated from HIV patients are all capable of invading human cells. Under the right circumstances (as in immunocompromised hosts), disease may occur.
Toxin production
M. pneumoniae bacteria produce a factor known as Community Acquired Respiratory Distress Syndrome (CARDS) toxin. CARDS toxin leads to inflammation and airway dysfunction. M. pneumoniae bacteria live primarily on the surface of epithelial cells in the respiratory system; however, these bacteria are capable of invading tissues and replicating intracellularly. CARDS assists in that process.
5. CDC/Cutchin. Image #22880. "This illustration depicted a three-dimensional (3D), computer-generated image, of a group of Mycoplasma pneumoniae, bacteria. The artistic recreation was based upon scanning electron microscopic (SEM) imagery." PHIL public domain. Created 2016. Accessed December 29, 2023. https://phil.cdc.gov/Details.aspx?pid=22880 6. CDC/Oosthuizen. Image #23243. "This is a medical illustration of drug-resistant, Mycoplasma genitalium bacteria." PHIL public domain. Created 2019. Accessed December 29, 2023. https://phil.cdc.gov/Details.aspx?pid=23243
