Cryptococcus is a yeast with a capsule that surrounds its cell. Cryptococcus belongs to the Phylum Basidiomycota, Subphylum Basidimycotina, Order Sporidiales, and Family Sporidiobolaceae in the yeast classification system.
Cryptococcus is a genus with 37 species. Only one of these, Cryptococcus neoformans, is a disease-causing species. This species is divided into three varieties based on antigenic differences in the capsule, differences in biochemical reactions such as the use of various sugars as nutrients, and differences in the shape of the yeast cells’ spores.
Cryptococcus neoformans var. gatti, grubii, and neoformans are the three varieties. In humans, the latter variety causes the most cryptococcal infections. Cryptococcus neoformans is found all over the world. It’s most commonly found on plants, fruits, and birds like pigeons and chickens.
Cryptococcus neoformans cause cryptococcosis, which is an infection caused by the bacteria Cryptococcus neoformans. Inhaling the microorganism causes it to grow indefinitely in the lungs. The pulmonary infection can be fatal for those with a weakened immune system, such as those suffering from Acquired Immunodeficiency Syndrome (AIDS).
In addition, yeast cells may spread throughout the body, causing inflammation of the nerve lining in the brain (meningitis).
Other infections and symptoms, such as infections of the eye (conjunctivitis), ear (otitis), heart (myocarditis), liver (hepatitis), and bone (osteitis), may be present (arthritis). Cryptococcal meningitis is the most common infection caused by the cryptococcal fungus.
AIDS patients are at the highest risk of contracting cryptococcosis. Those who have received an organ, are undergoing cancer chemotherapy, or have Hodgkin’s disease are also at risk, as their immune systems are frequently suppressed.
sAs the incidence of AIDS and the use of immunosuppressant drugs have grown over the past decade, the number of cases of cryptococcosis has risen.
Until then, cases of cryptococcus occurred only rarely. Even today, those with a well-functioning immune system are seldom at risk for cryptococcosis. For these individuals, a slight skin infection may be the only adverse effect of exposure to Cryptococcus.
Cryptococcus begins with the inhalation of Cryptococcus neoformans. Likely, the inhaled yeast is weakly encapsulated and is relatively small.
This enables the cells to penetrate the lungs’ alveoli. Capsule production takes place there. The capsule that surrounds each yeast cell aids the cell in avoiding the host’s immune response, particularly macrophage cell engulfment (which is called phagocytosis).
The capsule is made up of sugar chains, similar to the capsule that surrounds bacteria. Cryptococcus neoformans have a very negatively charged capsule. Because macrophages are negatively charged, repulsive forces will further prevent macrophages from interacting with the capsular material.
A yeast enzyme called phenol oxidase is another important virulence factor. The enzyme is involved in the synthesis of melanin.
The phenoloxidase is thought to prevent the formation of charged hydroxy groups, which can be harmful to yeast cells. To make the compound, the yeast may actually recruit the body’s melanin-producing machinery.
Other enzymes in Cryptococcus neoformans degrade certain proteins and the phospholipids that makeup cell membranes. These enzymes may aid in the disruption of the host cell membrane, allowing yeast cells to more easily penetrate host tissue.
Cryptococcus neoformans can grow in the human body at room temperature. The other Cryptococcus species are unable to withstand this high temperature.
Another virulence factor could be at work. Antigens from the yeast can induce a type of T cell that suppresses the host’s immune response, according to evidence from laboratory studies.
This is in line with the fact that cryptococcal meningitis survivors have a malfunctioning immune system for a long time after the infection has ended.
As a result, Cryptococcus neoformans may not only be capable of evading the host’s immune response but also of dampening it.
If the infection is treated while it is still confined to the lungs, the chances of a full recovery are good, especially in patients with a healthy immune system. Spread to the central nervous system, on the other hand, is dangerous, especially in immunocompromised patients.
Intravenous administration of a compound called amphotericin B is the standard treatment for cryptococcal meningitis.
Unfortunately, the drug has a number of negative side effects, including fever, chills, headache, nausea, vomiting, diarrhea, kidney damage, and bone marrow suppression.
The latter can result in a significant reduction in red blood cells. Amphotericin B is being studied in bags made of lipid material (called liposomes).
Rather than flooding the entire body with the drug, liposomes allow the drug to be more specifically targeted to the site where treatment is most needed. The use of liposome-delivered amphotericin B should hopefully reduce therapy’s side effects.