Lecture 7 - Fungus (Candida) Flashcards
T or F, The fungi Candida are commonly a part of the normal flora of the mouth, GI tract and genitourinary tract
True
Candidiasis usually results from what:
Defects in normal host defenses and/or lack of competitive normal flora:
- Periods of modified host flora - like during antibiotic treatment
- During periods of decreased host defense such as immunosuppressive therapies
Saprobe:
Organisms that live on dead or decaying organic matter
Parasites:
Organisms that live on or within a host from which they derive benefits without making any useful contributions in return
Fungal cell membrane is different from humans how?
It is similar to ours except for the addition of ergostal in contrast to cholesterol
- Many antifungal strategies are based on the presence of ergosterol in fungal membranes
What do Azoles do?
Inhibit ergosterol synthesis
What do polyenes do?
Bind and form pores in ergosterol-containing membranes rather than cholesterol containing membranes
Do fungi have cell wall?
Yes, fungi are surrounded by a multi-layered, rigid cell wall made up mainly of cross-linked glucans (another antifungal target)
Is there a large amount of effective anti fungals available to treat fungal infections? Why or Why not?
No, relatively few effective anti-fungals
- Because fungal cells, like mammalian cells, are eukaryotic and to develop something specific to fungal cells but nontoxic for human cells is difficult
Fungi can be divided into what two basic morphologies:
- Yeasts (single cells)
2. Hyphae or filamentous (multinucleated branched, mold-like)
What is mycelium
The collective term for a mass of hyphae (mycelium is also synonymous with mold)
Why is the morphology of some fungi not fixed?
Becasue some are dimorphic, that is, they can exist in both a filamentous or yeast morphology depending on conditions of growth
the morphology of Candida albicans is further complicated and fairly unique why?
They can be dimorphic - yeast-like or filamentous (true hyphae) - but can also assume a pseudohyphae morphology where cells are elongated and linked like sausages. thus they could be called POLYMORPHIC
What types of immunity are used to fight fungi?
Good innate defenses
Cellular immunity
Explain Fungal cell wall
B-1,4 N-AGM (Chitin wall)
What are the two major targets for anti-fungals
Cell wall
Sterols (ergosterol)
What serves as the primary barrier to fungal pathology?
Functioning epithelium. Healthy people have a very high level of innate immunity to fungal diseases
What things contribute to host resistance to fungus
- Fatty acids
- pH
- epithelial cell turnover
- normal bacterial flora
7 fungal pathologies
- Mycotoxicoses
- Hypersensitivities
- Superficial Mycoses
- Cutaneous Mycoses
- Subcutaneous Mycoses
- Systemic Mycoses
- Opportunistic Mycoses
Is mycotoxicoses rare or common?
Rare
Type I hypersensitivities like hay fever and asthma have what reaction to the pathology?
IgE mediated
Type IV hypersensitivities like contact dermatitis to fungal products:
Cellular immunity, Th, Tc, CK
What fungal pathology deals with outermost skin layers and hair and has no immune response?
Superficial mycoses
Cutaneous Mycoses is caused by what?
Dermatophytes
- Tricophyton species
- Micosporum species
- Epidermophyton species
What are the 3 major types of dermatophytes that causes cutaneous mycoses
- Tricophyton species
- Micosporum species
- Epidermophyton species
How are subcutaneous mycoses transfered?
Fungi/spores introduced via wounds
Systemic mycoses is passed how?
Lung infections (Inhaled spores) Inhaled
4 different groups found to cause opportunistic mycoses
- Candidiasis (Fairly common (oral and vagina))
- Cryptococcus (bird droppings)
- Aspergillosis (soil, spores infect lungs)
- Pneumocystis (yeast-like fungus, lung infections in in AIDS)
Why are oppportunistic mycoses a growing concern?
Because of AIDS, the growing use of immunosuppressive therapies and broad use of antibiotics
What hosts are commonly found with Candidiasis?
Candidiasis is a major disease problem of immunocompromised hosts
What is the #1 species of Candida?
C. albicans causing Oral, esophageal, and vaginal diseases
T or F, Candidiasis is a disease almost exclusively of immunocompromised individuals?
True
In acidic pH, what morphologic state will Candida be in?
The more acidic goes yeast –> Pseudohyphae
Less acidic would be true hyphae
Does a body’s adaptive or specific immunity help fight fungi?
No, yeast proteases degrade Ab and C3b so there is no effective humal immunity
What are the primary defenses against fungal infections
Innate and T cell-mediated (cellular)
What cells respond to fungal antigens by producing cytokines that galvanize anti-fungal immunte (innate and adaptive)
Th1 cells
Candida can act oppportunistically if …?
Either the innate defenses or adaptive immunity becomes compromised.
Primary oral candidiasis clinical presentations:
- Acute pseudomembranous (White)
- Erythematous (Red) - No pseudomembrane)
- Chronic Hyperplastic (Grey)
- Chronic mucocutaneous
Primary oral candiasis is presanet whre?
Only on oral and surrounding tissues
Secondary oral candidiasis is present where?
Oral tissues that are associated with other candidial infections at other mucosal and cutaneous sites.
A typical case of thrush =
Oral candidiasis
