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The study of fungi is termed _______________.
mycology
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Deseases caused by fungi are called __________.
mycosis
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State 4 ways fungi are beneficial to humans.
- Decay dead plants and animals.
- Used in manufacturing of various industrial and food products.
- Used in production of many common antibiotics.
- May be eaten as food.
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State 3 ways fungi are harmful to humans.
- Damage wood and fabrics.
- Spoil foods.
- Cause a variety of plant and animal diseases, including human infections.
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Fungi are _______________, requiring organic compounds for both an energy and carbon source, which obtain nutrients by _________ them from their environment.
- chemoheterotrophs
- absorbing
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What is the appearance of a typical yeast?
- Unicellular
- Oval or spherical
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What is the term for the asexual reproduction of yeasts, and describe the process?
Budding: a bud forms on the outer surface of a parent cell, the nucleus divides with one nucleus entering the forming bud, and cell wall material is laid down between the parent cell and the bud.
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In terms of Oxygen needs, yeasts are ________?
facultative anaerobes
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List 2 ways Saccharomyces is beneficial to humans.
- Used in baking
- Used in brewing
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Name 3 yeasts that infect humans.
- Candida albicans
- Cryptococcus neoformans
- Pneumocystis jiroveci
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Infections caused by Candida yeasts are called _________?
candidiasis
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Name 4 common forms of candidiasis.
- thrush (oral mucocutaneous candidiasis)
- vaginitis
- onychomycosis (infection of the nails)
- dermatitis (infections of moist skin)
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Describe 2 conditions that enable Candida to cause severe opportunistic systemic infections.
- humans that are immunosuppressed
- humans on broad spectrum antibiotics (Candida is eukaryotic, antibiotics are used against prokaryotic bacteria and do not effect Candida)
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Describe what a psuedohyphae is.
the budding yeast may elongate and remain attached producing a filament like structure (see Fig. 10 on pg 97 of lab book)
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Can Candida produce hyphae?
Yes, although Candida is a yeast, it can produce hyphae. The hyphae help Candida to invade deeper tissues after is colonizes the epithelium.
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Asexual spores called ____________ form in clusters along the hyphae of Candida.
blastoconidia (blastopores, see Fig. 2 on pg 95)
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Thick walled survival spores called ___________ may also form on the hyphae of Candida, under certain conditions.
chlamydoconidia (see Fig. 2 on pg 95)
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What is the usefullness of Saboraud Dextrose Agar (SDA)?
It inhibits bacterial growth and promotes fungal growth. It is selective for fungi.
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What is the usefullness of Mycosel Agar?
Mycosel Agar inhibits bacterial and saprophytic fungal growth. It is selective for pathogenic fungi.
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What is the usefullness of Rice Extract Agar?
It promotes the growth of hyphae, blastoconidia, and chlamydoconidia, structures unique to Candida albicans. It can be used to identify Candida infections.
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What is the name of the pathogenic yeast found in soil and actively grows on bird feces (usually pigeon and chicken droppings)?
Cryptococcus neoformans
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How is Cryptococcus neoformans transmitted to humans?
Usually inhaled my humans in dust containing bird feces.
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Where in the body does Cryptococcus neoformans usually infect?
The lungs (but it can disseminate to other parts of the body)
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If Cryptococcus neoformans disseminates from the lungs, what are the possible complications it causes? (Usually in immunosuppressed individuals.)
Meningoencephalitis (infection of the meninges)
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Information card:
Cryptococcus neoformans is and indicator disease of AIDS.
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What are the characteristics of Cryptococcus neoformans yeasts?
- Oval
- 5-6μm in diameter
- thick capsule (resists phagocytic engulfment)
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What are 3 methods to identify Cryptococcus neoformans?
- Preparing Indian Ink or nigrosin negative stains of suspected sputum or cerebral fluid, in which the encapsulated yeasts can be seen.
- It can be isolated on SDA and identified by biochemical testing.
- Use direct and indirect serological tests.
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Cryptococcus infections are termed _________.
cryptococcosis
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What is the name of the disease caused by Pneumocystis jiroveci?
Pneumocystis pneumonia (PCP)
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What 3 predisposing conditions a person is normally seen to have before contracting infections by Pneumocystis jiroveci?
- AIDS
- late stage malignancies
- leukemia
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Describe the appearance of Saccharomyces cerevisiae on SDA.
On SDA there is + growth that is white and creamy in apprearance, and smells like fresh bread or stale beer.
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Describe the appearance of Candida albicans on SDA.
On SDA there is + growth that is white and creamy in apprearance, and smells like fresh bread or stale beer.
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Describe the appearance of Saccharomyces cerevisiae on Mycosel Agar. (-growth)
Saccharomyces cerevisiae does not grow on Mycosel Agar.
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Describe the appearance of Candida albicans on Mycosel Agar.
On Mycosel Agar there is + growth that is white and creamy in apprearance.
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When given a plate of Mycosel Agar showing yeast-like growth and a plate of Rice Extract Agar showing hyphae, blastospores, and chlamydoconidia, what yeast can you identify from these plates?
Candida albicans
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Information card:
Review the pictures you drew in your lab results and on pages 95 and 97, to be able to identify microscopically:
-Saccharomyces cerevisiae in gram stain
-Candida albicans in gram stain
-positive specimen of thrush by the presence of budding Candida albicans.
-Cryptococcus neoformans in indian ink
-a cyst of Pneumocystis jiroveci in lung tissue.
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When viewed microscopically, what is the characteristic appearance of Pneumocystis jiroveci?
It has a crushed ping pong ball appearance.
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Define hyphae.
Branching, tubular structure from 2-10μm in diameter and is usually divided into eukaryotic cell-like units by crosswalls called septa.
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Define mycelium.
The total mass of hyphae.
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Define vegetative mycelium.
The portion of mycelium that anchors the mold and absorbs nutrients.
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Define aerial mycellium.
The portion of mycellium that produces asexual reproductive spores.
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Are molds prokaryotic or eukaryotic?
eukaryotic
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What is the name of the mold spores that are borne externally in chains on an aerial hyphae?
Conidiospores
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Name 2 types of molds that produce condiospores.
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What is the name of the mold spores that are produced within a sac or sporangium on an aerial hyphae?
Sporangiospores
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Name a type of mold that produces sporangiospores.
Rhizopus
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Name 3 principle ways molds reproduce asexually.
- Condiospores
- Sporangiospores
- Arthrospores
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What are the 2 main criteria used in identifying molds.
- The form and manner in which spores are produced.
- The appearance of the hyphae and mycelium.
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Name 3 types of Non-Pathogenic molds.
- Penicillium
- Aspergillus
- Rhizopus
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Describe the appearance of Penicillium grown on SDA.
Fuzzy grey, green, or blue mold.
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Describe the appearance of Aspergillus grown on SDA.
Fuzzy black mold.
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Describe the appearance of Rhizopus grown on SDA.
Fuzzy white mold with fuzzy black edge.
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Information card:
Study pictures on pages 104 and 105 and be able to identify Penicillium, Aspergillus, and Rhizopus microscopically.
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Rhizopus can reproduce sexually as well as asexually. What is the name of the structure Rhizopus uses to reproduce sexually?
Zygospore
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What is a dermatophyte mold?
A group of molds that cause superficial mycoses of the hair, skin, and nails.
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What is the name of the protein that humans produce that is used by dermatophyte molds?
Keratin: it's used as a nitrogen and energy source.
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Infections of dermatophyte molds are commonly called?
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What are the 3 common genera of dermatophyte molds?
- Microsporum
- Trichophyton
- Epidermophyton
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Name 6 types of dermatophyte mold infections.
- Tinea capitis (head)
- Tinea barbae (face and neck)
- Tinea corporis (body)
- Tinea cruris (groin)
- Tinea unguium (nails)
- Tinea pedis (ahtlete's foot)
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Describe what macroconidia on dermatophyte molds are.
Large leaf or club-shaped asexual spores.
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Describe what microconidia on dermatophyte molds are.
Small spherical asexual spores.
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Describe how dermatophytes can be identified by potassium hydroxide preparations of tissue scraping.
Tissue scrapings are digested with 10% potassium hydroxide (which causes lysis of the human cells but not the fungus) and examined microscopically for the presence of fungal hyphae and spores.
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Describe how dermatophytes can be identified by Dermatophyte Test Medium (DTM).
DTM has phenol red as a pH indicator with the medium yellow (acid) prior to inoculation. As the dermatophyte utilizes the keratin in the medium, they produce alkaline end products that raise the pH and turn the phenol red in the medium from yellow (acid) to red (alkaline).
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Describe how dermatophytes can be identified by Saboraud Dextrose Agar (SDA).
The types of macroconidia and microconidia can be observed by growing mold on SDA and observing under a microscope. Many dermatophytes produce
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Define dimorphic (systemic) fungi.
Outside of the body they grow as mold, but inside the body they grow as a yeast-like form.
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How do humans contract dimorphic fungal infections?
By inhaling spores from the mold form of the fungi.
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Name 3 common dimorphic fungal infections in the U.S., and where they are found geographically.
- Coccidioides immitis - Southwestern U.S.
- Histoplasma capsulatum - Great Lakes region, Mississippi and Ohio River valleys, and Eastern U.S.
- Blastomyces dermatitidis - Great Lakes region, Mississippi and Ohio River valleys.
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How do humans contract Coccidioides immitis?
The mold form grows in arid soil and produces arthrospores. Humans inhale the arthrospores along with dust.
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How do humans contract Histoplasma capsulatum?
The mold form grows on bird and/or bat droppings or soils contaminated with the droppings and produces large tuberculate macroconidia and microconidia. Humans inhale spores along with contaminated soil.
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How do humans contract Blastomyces dermatitidis?
The mold form with condiospores grows on bird droppings and soils contaminated with the droppings. Humans inhale spores or enter breaks in the skin.
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Describe the mold and nonmycelial forms of Coccidioides immitis.
The mold form has vegetative hyphae (mycelium) that produce arthrospores. Once inhaled the arthrospores germinate and form endosporulating spherules.
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Describe the mold and nonmycelial forms of Histoplasma capsulatum.
The mold form has vegetative hyphae (mycelium) with tuberculate macroconidia and microconidia. Once inhaled the spores germinate in the lungs and the then grows as a budding, encapsulated yeast.
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Describe the mold and nonmycelial forms of Blastomyces dermatitidis.
The mold form produces mycelium with small condiospores. Once spores are inhaled or enter breaks in the skin, they germinate and the fungus grows as a yeast having a characteristic thick cell wall.
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Define bacteriophage.
Viruses that only infect bacteria.
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Define plaque.
A small, clear area on an agar plate where the host bacteria have been lysed as a result of the lytic life cycle of the infecting bacteriophage.
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Define phage typing.
A process used to identify bacteriophage by infecting a known species of bacteria with an unknown species of bacteriophage and observing if plaques are formed. Bacteriophages are species specific and if the phage forms plaques on the bacterial growth you can positively identify the virus by the bacteria it attacks.
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Describe the structure of the bacteriophage; Coliphage T4 (infects E. coli).
Capsid (head), nucleic acid, sheath, pins, tail fibers
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Describe the lytic life cycle of bacteriophage.
- 1. Adsorption; bacteriophage attaches to cell with tail fibers.
- 2. Penetration; bacteriophage "drills" a hole in cell and injects its genome. This begins the eclipse period.
- 3. Replication; cell shut down and take over, cell begins to replicate viral DNA and build viral components.
- 4. Maturation; viral components are assembled.
- 5. Release; Bacteriophage coded lysozyme breaks down the bacterial PG causing osmotic lysis of host cell and release of bacteriophages.
- 6. Reinfection; 50-200 bacteriophages are release to infect surrounding bacteria.
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Define viral specificity.
Specific strains of bacteriophage will only adsorb to a specific strain of susceptible host bacterium.
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Name the bacterial family to which the most commonly encountered organisms isolated from clinical specimens belong.
Enterobacteriaceae
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List 5 characteristics used to place bacteria into the family Enterobacteriaceae.
- 1. They are gram-negative rods.
- 2. If motile, they possess a peritrichous arrangement of flagella.
- 3. They are facultative anaerobes.
- 4. They are oxidase negative.
- 5. All species ferment glucose.
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What infections are caused by Salmonella, and how is transmitted to humans?
Enteritis is the most common form of salmonellosis. Animals carry Salmonella in their intestines, people usually become infected from ingesting improperly refrigerated, uncooked or undercooked poulty, eggs, meat, or dairy products contaminated with animal feces.
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What infections are caused by Shigella, and how is transmitted to humans?
Any Shigella infection is called shigellosis. Shigella only infects humans and infects through the ingestion of water or shellfish contaminated with human or animal feces.
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Name 6 genera of Enterobacteriaceae considered as common opportunistic pathogens that reside as normal flora in the intestinal tract.
- Escherichia coli
- Proteus
- Enterobacter
- Klebsiella
- Citrobacter
- Serratia
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Name 4 common types of infections that normal intestinal flora opportunistic bacteria cause.
- Urinary tract infections
- wound infections
- pneumonia
- septicimia
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Name the most common non-fermentive gram-negative rod that infects humans.
Pseudomonas aeruginosa
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Name 5 types of opportunistic infections caused by Pseudomonas aeruginosa.
- Urinary tract infections
- Wound infections
- Pneumonia
- Septicema
- Burn infections
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State the usefullness of XLD agar for the isolation of Enterobacteriaceae and Pseudomonas.
XLD agar is selective for gram negative bacteria.
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State the usefullness of Pseudosel agar for the isolation of Enterobacteriaceae and Pseudomonas.
Pseudosel agar is selective for Pseudomonas aeruginosa.
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State how to differentiate P. aeroginosa from the Enterobacteriaceae using the following tests:
1. Oxidase test
2. Fermentation of glucose
3.Production of pigment and fluorescent products
4. Odor
- 1. Enterobacteriaceae is negative, P. aeruginosa is positive
- 2. Enterobacteriaceae is positive, P. aeruginosa is negative
- 3. Enterobacteriaceae is negative, P. aeruginosa is positive
- 4. Enterobacteriaceae have a foul smell, P. aeruginosa have a fruity or grape juice-like aroma
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Describe the Enterotube II.
The Enterotube II is a self-contained, compartmented plastic tube containing 12 different agars (enabling the performance of a total of 15 standard biochemical tests) and an enclosed inoculating wire.
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