6.6 Medical Mycology Flashcards
Are fungi Eukaryotic or prokaryotic?
Eukaryotic with organelles and nucleus
What molecule is in the cell membrane of Fungi?
Sterols present (ergosterol)
What molecules are present in the cell wall of fungi?
- Polysaccharides including chitin
- Polymer of N-acetylglucosamine
- alpha-1,3 glucan (not in humans) Target for drugs
- beta-1,3-glucan (not in humans)
- Galactomannan
What is the 02 utilization methods for Fungi?
aerobic to obligate anaerobes
What is the doubling time of Fungi?
usually hours, more complex than bacteria that can double in minutes.
What are the functions and reproduction methods of spores in fungi?
- Mainly asexual, but can reproduce sexually
- Functions include survival and dissemination
What percent of infections are fungi related and why have the number of diagnosis increase over the recent years?
- 20% of infections are fungus related
- Increased diagnosis due to more immunosuppressed and better at diagnosis
What are risk factors for fungal infections?
- Living in a warm, humid climate
- Occupational (outdoor jobs, landscaper)
- CMI deficiency
- Cell mediated immune issues/defects
- Higher incidence more intractable
- Neutrophil, T-cell mediated response most important.
- Mostly environmental, not endogenous
- Some are normal microbicota
- Infections tend to be subacute to chronic, not usually acute
What are the three types of mycoses?
1) Superficial/cutaneous
2) Subcutaneous
3) Systemic
Describe Superficial/cutaneous fungi infections
- hair, skin, nails
- most common
Describe Subcutaneous mycoses
- beneath the skin
- Rare, tropical (Mexico)
Describe Systemic mycoses
- Deep within body
- Characteristic geographic regions (endemic mycoses)
- Coccidioides immitis, southwestern U.S., Mexico, Central and South America
Describe Opportunistic Fungi
- Only in immunocompromised, debilitated, or break in skin or mucous membrane
- Normal microbiota or environmental fungi
- Aspergillosis, candidiasis, cryptococcosis, mucormycosis
Describe Primary Pathogens Fugi
- Infects healthy individuals
- Examples: Histoplasmosis, blastomycosis, coccidioidomycosis, paracoccidioidomycosis
- Only environmental, soil, or vegetation
- Can be inhaled causing lung infections
- Conidia or hyphal fragments
Describe Unicellular Yeast
1) Unicellular eukaryotes
2) round/oval, look like bacterial colonies on agar plates.
3) ~10 times bigger than bacterial cells
4) Usually reproduce by budding
5) Divide asymmetrically
6) Buds= blastoconidia
7) May fail to detach or form a short chain of cells called pseudohypha
Describe multicellular molds
1) Multicellular, filamentous eukaryotes
2) Branching cylindric tubules called hyphae that can penetrate tissues. These grow from the tips and are multinucleate.
3) Mass of hyphae=mycelium
4) Part of mycelium involved in gaining nutrients=vegetative mycelium
5) Part of mycelium is involved in growth and reproduction
What is macroconidia?
Relatively large, complex conidia
What is microconidia?
Smaller, more simple conidia
What is a sporangium?
Sack that sporangiospores are in
Are conidia in a sack?
No
Conidiophore(stem) spores are called?
Conidiospores (no sack)
Sporangiophore(stem) spores are called?
Sporangiospores (sack surrounds spores)
Describe Dimorphic Fungi
- At low temperature in the soil the fungi grows as a filamentous fungus (mold)
- After being inhaled into the lungs the dimorphic fungi undergoes a morphological switch triggered by the change in temperature and become yeast like.
- can form hyphae in vivo and penetrate/spread
- Affects expression cell wall glycoproteins, proteolytic enzyme secretion, susceptibility to oxidative damage in neutrophils, adaptation to new environments.
- Makes harder for human immune system to fight due to switching.
What is a Blastoconidia?
Buds formed by yeast
What is a Pseudohyphae?
Branching cylindric tubules
What are Septate?
Having or partitioned by a septum or septa.
What is Coenocytic?
An organism made up of a multinucleate, continuous mass of protoplasm enclosed by one cell wall, as in some fungi or algae.
What is Mycelium?
Mass of Hyphae
What are the function of Fungal spores?
Reproduction, survival, and transmission
What is the top virulence factor in fungi?
Dimorphism
What are some other virulence factors in fungi?
1) Adhesins
2) Proteases, elastases, phospholipases (cut through tissues
3) Some resist killing in macrophages
4) Sidrophores
5) Biofilms
What is the main way that fungi cause injury to the body?
Injury is largely due to destructive aspects of delayed type hypersensitivity (DTH) response as result of immune system being unable to clear. Cell mediated response like TB
Which fungi has a capsule?
Cryptococcus neoformans. In environment it lacks capsule, but gains it when infecting humans.
How do you stain a fungi capsule?
Negitive stain with India ink
What is siderophores?
A molecule that binds and transports iron in microorganisms.
What does a high alpha 1,3-glucan content in yeast walls do as a virulence factor?
Helps mask other immunogenic molecules.
What is the best rapid, cost-effective diagnosis of fungal infection?
Direct microscopic examination of clinical specimens.
What stains and chemicals are used on fungi?
- 10% KOH
- Stains: Lactophenol cotton blue, Gram, silver, calcofluor white (fluorescent).
What Gram stain do most fungus stain as?
Gram positive
What is common yeast morphology?
- Size, wall thickness, capsule present/absent
- Size, shape, appearance, spores
- Hyphae, septate, or coenocytic, type branching.
What are two typical media for clinically important fungi?
- SDA= Sabouraud Dextrose Agar
- SABHI- Sabouraud dextrose media+ BHI media
What is a molecular way to identify different species of fungi?
Each species of pathogen carries unique DNA or RNA signature that differentiates it from other organisms. Examples: Nucleic acid amplification, nucleic acid probes, and microarrays. Fast sensitive specific.
