Fungi use a range of virulence factors to attach to host tissues, invade them, resist immune defenses, and damage the host. Many of these mechanisms resemble those found in bacteria, even though fungi are eukaryotes. This lesson focuses on examples from Candida, Cryptococcus, Claviceps, and Aspergillus.
Candida albicans is an opportunistic fungus that can cause oral thrush, vaginal yeast infections, and cutaneous candidiasis. Its surface adhesins, which are glycoproteins, bind to phospholipids on epithelial and endothelial cells. This attachment helps the fungus remain on host surfaces.
All flashcards
How do *Candida albicans* adhesins contribute to infection?
These surface glycoproteins bind phospholipids on epithelial and endothelial cells, helping the fungus attach to host tissues.
How does the *Cryptococcus* capsule promote virulence?
Its polysaccharide capsule, composed mainly of glucuronoxylomannan, helps the fungus resist phagocytosis.
What effects does *Aspergillus* gliotoxin have on host defenses?
It can induce host-cell self-destruction and impair phagocytic cells and pro-inflammatory responses.
What is antigenic variation?
It is a pathogen's ability to alter recognizable surface molecules, helping it evade or delay immune elimination.
How can helminths suppress host immunity?
Some produce proteases that degrade host antibodies or other substances that suppress innate and adaptive responses.
Quiz questions
Which host-cell components do *Candida albicans* adhesins bind to, supporting attachment to epithelial and endothelial tissues?Answer: Phospholipids on the host-cell surfaces.
Why are nonencapsulated *Cryptococcus* cells generally less virulent than encapsulated cells?Answer: They are more readily engulfed by phagocytes.
How does *Claviceps purpurea* ergot toxin reduce blood flow to the extremities?Answer: It causes vasoconstriction, which can lead to gangrenous ergotism.
How does antigenic variation help *Plasmodium falciparum* persist in a host?Answer: The parasite changes PfEMP1's structure, making consistent immune recognition harder.
How do *Schistosoma mansoni* larvae penetrate intact skin?Answer: They use proteases that degrade skin proteins, including elastin.
Based on Microbiology by Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu, Philip Lister, Brian M. Forster (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.