Final answer:
Cryptococcus neoformans var neoformans includes serotypes C and D and is a fungal pathogen that causes cryptococcal meningitis, which can be severe in immunocompromised individuals. It evades the immune system with its thick capsule, making treatment challenging.
Step-by-step explanation:
Cryptococcus neoformans var neoformans is a fungal pathogen known to cause cryptococcal meningitis, an infection that can be particularly severe in immunocompromised patients, such as those with AIDS. This pathogen includes serotypes C and D. It is commonly found in soil and bird droppings, and infections are usually acquired through inhaling basidiospores that become aerosolized. In individuals with healthy immune systems, the infection may cause subclinical respiratory infections; however, in those with weakened immune defenses, it can progress to meningitis and granuloma formation in the brain. For treatment, antifungal drugs like amphotericin B and flucytosine are used, often for a prolonged period due to the difficulty these drugs have in crossing the blood-brain barrier and their potential side effects.
The extensive capsule of C. neoformans is a major virulence factor, enabling it to evade phagocytosis by alveolar macrophages. This makes the fungus more difficult to clear from the body, necessitating aggressive and lengthy treatment protocols. The capsule is primarily composed of the polysaccharide glucuronoxylomannan, and this characteristic is visible under a microscope with certain stains such as India ink or when observing the negative stain micrographs of the fungal cells.