Mycology and Fungal Infections: Definitions, Diagnostics, and Treatments

Define Saksenaea vasiformis.

Forms a typical flask-shaped sporangium arising from darkly pigmented rhizoids.

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Answer

Describe Penicillium marneffei.

To date, all naturally occurring infections have been in residents of or travelers to Southeast Asia, especially northern Thailand, Vietnam, Hong Kong, Taiwan, and southern China.

Define mycotic keratitis.

Prolonged treatment with corticosteroids may also be a predisposing factor.

Define phaeohyphomycosis.

A mycotic infection of humans and lower animals caused by a number of dematiaceous (brown-pigmented) fungi where the tissue morphology of the causative organism is mycelial.

Define rhinosporidiosis.

An infection of the mucocutaneous tissue caused by an as yet unisolated and unclassified fungus.

What is the expected result when performing a microscopic examination of a Tinea Nigra clinical sample using a 10% KOH stain?

The identification of pigmented yeast cells.

Histoplasma capsulatum is endemic in the Ohio and Mississippi River valleys.

True.

Both Mycetoma and Mycotic Keratitis are primarily characterized as subcutaneous infections that require surgical excision and X-ray imaging to determine if the fungus has spread to the underlying bone tissue.

False.

Which of the following describes the primary challenge in achieving selective toxicity when developing antifungal drugs compared to antibacterial drugs?

Fungi are eukaryotic organisms, sharing many cellular structures with human hosts.

Describe Pseudallescheriasis and Scedosporium.

A spectrum of diseases similar in terms of variety and severity to those caused by Aspergillus. The vast majority of infections are mycetomas.

Which of the following best describes the clinical presentation and typical distribution of Tinea Nigra lesions?

Asymptomatic, non-inflammatory brown or black macules often located on the palms.

Define amphotericin B.

Binds to ergosterol within the fungal cell membrane resulting in depolarization of the membrane and the formation of pores.

Describe subcutaneous zygomycosis.

Primary cutaneous and subcutaneous infections usually result from a barrier break or traumatic implantation of fungal elements.

Fungal hyphae have a hard wall containing chitin.

True.

Describe sporotrichosis.

Secondary spread to articular surfaces, bone, and muscle is not infrequent, and the infection may also occasionally involve the central nervous system, lungs, or genitourinary tract.

Define systemic zygomycosis.

An acute and rapidly developing, less commonly chronic infection of debilitated patients. Depending on the portal of entry, the disease involves the rhino-facial-cranial area, lungs, gastrointestinal tract, skin, or less commonly other organ systems.

Define histoplasmosis.

An intracellular mycotic infection of the reticuloendothelial system caused by the inhalation of the fungus.

Define Penicillium marneffei.

Exhibits thermal dimorphism by growing in living tissue or in culture at 37°C as a yeast-like fungus or in culture below 30°C as a mold.

Which of the following is a common diagnostic method used to determine if a Mycetoma infection has progressed to involve the bone?

X-rays of the affected area.

Which is NOT a factor causing dandruff?

The environment.

Define pityriasis versicolor.

A chronic superficial fungal disease of the skin characterized by well-demarcated white, pink, fawn, or brownish lesions.

Disseminated Histoplasmosis is more common in patients with AIDS.

True.

Describe Malassezia infections.

Chronic benign skin disorder.

Define mycotic keratitis.

An opportunistic fungal infection of the eye that causes ulceration and inflammation, usually following trauma to the cornea by vegetative matter, soil, or surgery.

Describe subcutaneous zygomycosis.

Lesions vary considerably in morphology but include plaques, pustules, ulcerations, deep abscesses, and ragged necrotic patches. Most heal with little treatment (debridement and amphotericin B) and are not usually associated with dissemination.

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Histoplasma capsulatum is dimorphic.

True.

Define mycetoma.

A mycotic infection of humans and animals caused by a number of different fungi and actinomycetes characterized by draining sinuses, granules, and tumefaction.

Define Malassezia furfur.

A lipophilic yeast forming part of the normal flora of human skin.

Define histoplasmosis.

Five percent of the cases have chronic progressive lung disease, chronic cutaneous or systemic disease, or an acute fulminating fatal systemic disease. All stages of this disease may mimic tuberculosis.

Define Dixon's agar.

A specialized isolation medium containing glycerol-mono-oleate.

Malassezia is associated with diaper rash.

False.

Define rhinocerebral zygomycosis.

An acute and rapidly developing, less commonly chronic infection of debilitated patients. Depending on the portal of entry, the disease involves the rhino-facial-cranial area, lungs, gastrointestinal tract, skin, or less commonly other organ systems.

Histoplasma capsulatum is found in bat

chicken, and bird feces.,True.

Describe systemic zygomycosis.

The infecting fungi have a predilection for invading vessels of the arterial system, causing embolization and subsequent necrosis of surrounding tissue. A suppurative, pyogenic reaction is elicited; granuloma formation is not frequently encountered.

Define mycetoma.

Worldwide but most common in barefoot populations living in tropical or subtropical regions.

Define paracoccidioidomycosis.

A chronic granulomatous disease, often inapparent, that disseminates to form ulcerative granulomata of the buccal, nasal, and occasionally gastrointestinal mucosa.

Define phaeohyphomycosis.

Clinical forms range from localized superficial infections of the stratum corneum (tinea nigra) to subcutaneous cysts (phaeomycotic cyst) to invasion of the brain.

Describe sporotrichosis.

Primarily a chronic mycotic infection of the cutaneous or subcutaneous tissues and adjacent lymphatics characterized by nodular lesions that may suppurate and ulcerate.

Define Loboa loboi.

Masses of spheroidal, yeast-like organisms.

Describe rhinosporidiosis.

Causes a chronic granulomatous disease characterized by the production of large polyps, tumors, papillomas, or wart-like lesions. The nose is the most commonly affected site.

false

The pathogen Pseudallescheria boydii is considered a "teleomorph," which refers to the asexual state of the fungus, while Scedosporium apiospermum refers to the sexual state.

How does a subcutaneous phaeohyphomycosis infection typically begin and progress in immunocompromised patients?

It begins as a single red nodule on the extremities and can develop into cysts.

false

Polyene antifungals like Amphotericin B and Echinocandins like Caspofungin are both considered broad-spectrum treatments because they target the fungal cell membrane, making them equally effective against Cryptococcus neoformans and Aspergillus species.

Define flucytosine.

Converted by cytosine deaminase into 5-fluorouracil, which is then converted into 5-fluorouridine triphosphate and incorporated into fungal RNA, leading to miscoding.

All of the following are properties of Histoplasmosis EXCEPT?

When mycelia (microconidia) reach the gut, they are converted to yeast form.

What is the primary difference between the Imidazole and Triazole subclasses of azole antifungals?

Imidazoles contain a five-member ring with two nitrogen atoms, while Triazoles have three.

Define tinea nigra.

Caused by Hortaea werneckii, a common saprophytic fungus found in soil, compost, humus, and wood in humid tropical and subtropical regions.

Why are Echinocandins, such as Caspofungin, ineffective against the pathogen Cryptococcus neoformans?

Cryptococcus neoformans lacks the specific glucan synthase enzyme targeted by the drug.

Describe lobomycosis.

A chronic, localized, subepidermal infection characterized by the presence of keloidal (raised fibrous scar tissue) lesions.

Which fungal species is specifically noted for producing multicellular conidia (dictyoconidia) in corneal scrapings?

Alternaria alternata.

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Microsporum audouinii best described as

Non-inflammatory infections of the scalp and skin, especially in children.

Epidermophyton floccosum best described as

Ringworm, athlete's foot, and jock itch.

Mucormycosis (a type of zygomycosis) is best described as

Caused by Rhizopus or Mucor in patients with ketoacidosis.

Mycelium concerned with reproduction.

Aerial mycelium.

What is the primary mode of transmission for Coccidioidomycosis?

Inhalation of arthroconidia fragments.

Microsporum canis best described as

A frequent cause of ringworm in humans, especially children. Invades hair, skin, and rarely nails.

Blastomycosis best described as

A chronic granulomatous and suppurative disease having a primary pulmonary stage.

Candidiasis best described as

Caused by Candida albicans.

Any fungal infection is called a mycosis.

True.

Conidiospores are ________?

Produced in a chain at the end of a conidiophore.

Microsporum ferrugineum best described as

An anthropophilic fungus causing epidemic juvenile tinea capitis in humans.

Dermatophytes all digest keratin.

True.

Multicelled conidiospores are called ________?

Macroconidia.

Yeast reproduce by?

Budding.

Which of the following is not normally used to identify molds in the lab?

Requirement for oxygen.

Mycelium concerned with obtaining nutrients.

Vegetative mycelium.

The fungi are most closely related to the ________?

Animals.

Trichophyton equinum best described as

Causing equine ringworm and rare infections in humans. Most strains require nicotinic acid for growth.

Aspergillosis best described as

Caused by inhalation of Aspergillus spores.

All of the following are true of the Zygomycota EXCEPT?

Have asexual zygospores.

Trichophyton tonsurans best described as

Anthropophilic fungus causing inflammatory or chronic non-inflammatory finely scaling lesions of skin, nails, and scalp.

Zygospores are ________?

Large spores enclosed in a thick wall and formed from the fusion of two cells.

Sporangiospores are formed at the end of an aerial hyphae.

True.

Which is NOT a characteristic of subcutaneous mycoses?

Secondary bacterial infections are required.

Microsporum nanum best described as

A zoophilic fungus frequently causing chronic non-inflammatory lesions in pigs and a rare cause of tinea in humans.

Which of the following best describes the fungi?

Chemo-heterotrophs.

Arthrospores are ________?

Formed by the fragmentation of septate hyphae.

Tinea capitis is a ringworm scalp infection while tinea corporis is a ringworm skin infection.

True.

Grocott's methenamine silver (GMS) stain reacts with fungal cell wall polysaccharides.

True.

Chromoblastomycosis is most commonly associated with which mode of transmission and geographic distribution?

Traumatic implantation of fungi into the skin in tropical and subtropical regions.

Trichophyton mentagrophytes var. mentagrophytes best described as

A wide range of animal hosts including mice, guinea pigs, kangaroos, cats, horses, sheep, and rabbits. Produces inflammatory skin or scalp lesions in humans, particularly rural workers.

Microsporum gypseum best described as

May cause infections in animals and humans, particularly children and rural workers during warm humid weather. Usually produces a single inflammatory skin or scalp lesion.

Ascomycota best described as

Common molds; asexual reproduction by conidia.

Trichophyton concentricum best described as

Causes chronic widespread non-inflammatory tinea corporis known as tinea imbricata because of the concentric rings of scaling it produces.

Tinea unguium best described as

Infection of the nails.

Which of the following is considered the hallmark diagnostic feature required for the identification of Chromoblastomycosis?

Detection of microscopic sclerotic bodies (copper pennies).

Which characteristic feature is commonly used to identify Cryptococcus neoformans using India ink staining?

A prominent visible polysaccharide capsule.

Aspergillosis (mycotoxicosis) best described as

Due to ingestion of contaminated foods containing mycotoxins.

Trichophyton rubrum best described as

The most common and widely distributed dermatophyte of humans. Frequently causes chronic infections of skin, nails, and rarely scalp.

Tinea pedis best described as

Athlete's foot.

Cutaneous mycoses best described as

Ringworm.

Thrush is an infection of the mouth and throat.

True.

What is the most common diagnostic method for Coccidioidomycosis?

Testing for IgM and IgG antibodies.

Trichophyton mentagrophytes var. quinckeanum best described as

Cause of mouse favus seen on mice as thick saucer-shaped yellow crusted lesions (scutula). Human infections are usually inflammatory and may also produce scutula.

Hyphomycetes best described as

Conidial molds with no sexual reproductive state.

Fungi capable of growing as a yeast or a mold are known as?

Dimorphic.

Long filaments that make up molds.

Hyphae.