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Pathology > Mycology I > Flashcards

Mycology I Flashcards

1
Q

What is the cell wall of fungi made of?

A

Chitin

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2
Q

What is the predominant sterol in fungi?

A

Ergosterol

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3
Q

Hyphae

A

There are a long, branching filamentous structure

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4
Q

Germ Tube

A

A germ tube is an outgrowth produced by spores of spore-releasing fungi during germination. The germ tube differentiates, grows, and develops by mitosis to create somatic hyphae.

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5
Q

Pseudohyphae

A

Sausage linked looking hyphae that from from a germ tube

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6
Q

Conidia

A

Conidia, sometimes termed asexual chlamydospores, or chlamydoconidia are asexual, non-motile spores of a fungus

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7
Q

Arthroconidia

A

It is when pieces of hyphae break off and each piece becomes spore forming

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8
Q

Phialide

A

It is a flask-shaped projection from the vesicle (dilated part of the top of conidiophore) of certain fungi.

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9
Q

What are the forms of dimorphic fungi and when are they seen?

A
  • Yeast like cells at 35 C
  • Mold form at 25 C

“Yeast in the heat, mold in the cold”

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10
Q

What is the most common opportunistic fungal pathogen?

A

Candida

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11
Q

Where is Candida found?

A

Normal flora of GI and GU tracts

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12
Q

What are the only species of Candida that forms germ tubes?

A

C. albicans and C. dubliensis

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13
Q

What Candida has the highest prevalence from oral or fecal specimens of HIV-positive patients?

A

C. dubliniensis

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14
Q

What Candida is resistant to fluconazole?

A

C. glabrata

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15
Q

What in Candida activates the complement system?

A

Cell wall mannan activates the alternate complement pathway leading to enhanced phagocytosis and killing of Candida

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16
Q

What are the risks for Candida infection?

A
  • Antibiotic therapy
  • Corticosteroid use
  • Decreased T cell function
  • Diabetes
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17
Q

What types of Candida albicans infection can be seen?

A
  • Mucocutaneous
  • Skin and nail
  • Vulvovaginal
  • Urinary tract infection
  • Meningitis
  • Endophthalmitis
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18
Q

What are the stains for C. albicans?

A
  • Gram stain

- Calcofluor stain

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19
Q

What are the spores typically produced by C. albicans?

A

Candida albicans, and Candida dubliniensis, are the two Candida spp. that produce a typical asexual spore, chlamydospores

20
Q

What are the characteristics of aspergillum?

A
  • Rapidly growing mold
  • Found in soil, air, construction dust
  • Dichotomous branching
  • Septate hyphae
21
Q

What is the angle of branching in Aspergillus?

A

45˚

22
Q

What is the most important Aspergillus species?

A

A. fumigatus

23
Q

What is the pathogenesis of A. fumigatus?

A
  • Inhale spores / conidia
  • Conidia bind to fibronectin
  • A. fumigatus inhibits alternate complement pathway and interferes with opsonization
24
Q

What are some possible clinical manifestations of A. fumigatus infection?

A
  • Allergic aspergillosis
  • Fungus ball in pre-existing cavity (TB, emphysema)
  • Invasive apergillosis
  • Dissemination infection
25
Q

What are the 2 families of fungi that cause murcomycosis?

A

Mucoraceae and Cunninghamellacea

26
Q

Where are the agents of murcomycosis found?

A

Agents of mucormycosis commonly found on fruit, bread, and in soil and are common components of decaying organic debris

27
Q

What type of patients does murcomycosis typically occur in?

A

Immunocompromised

28
Q

What species is most commonly associated with murcomycosis?

A

Rhizopus arrhizus

29
Q

What is the typical pattern and presentation of R. arrhizus invasion?

A

R. arrhizus have a predilection for invading major blood vessels, with ensuing ischemia, necrosis, and infarction of adjacent tissues, resulting in the production of black pus.

30
Q

Who is at risk for Rhizopus infection?

A

Patients with granulocytopenia, hematopoietic stem cell transplant and solid organ transplant recipients, and patients with underlying acidosis.

31
Q

What are some risk factors for Rhizopus infection?

A
  • Acidotic diabetics
  • Malnourished children
  • Severely burned patients
  • Severe leucopenia
  • Immunosuppressive disorders
32
Q

Rhinocerebral mucormycosis

A

– Most frequent presentation overall and classically affects diabetics with ketoacidosis
– Usually presents with facial and/or eye pain, proptosis and progressive signs of involvement of orbital structures - death within a few days

33
Q

What is the best option to make treatment better for murcomycosis?

A

Early diagnosis

34
Q

What is the branching angle seen in murcomycosis?

A

90˚

35
Q

What are the diagnostic features of murcomycosis?

A
  • Microscopic examination of tissues for broad, non septated hyphae
  • Growth is woolly white to grey
  • Examination of culture for characteristic sporangia
36
Q

Dermatophytosis

A

Fungal Infection of keratinized tissues (skin, hair, nails) caused by a group of specialized fungi, the dermatophytes

37
Q

What are the 3 genera of dermatophytes?

A

– Epidermophyton – 2 species
– Microsporum – 16 species
– Trichophyton – 24 species

38
Q

What does “ringworm” refer to in dermatophytosis?

A
  • Inflammation often greatest at the advancing margin leaving a central area with some clearing
  • The name “ringworm” follows from the irregular inflammatory border of the skin lesion
39
Q

Tinea Pedis

A

Athlete’s Foot

40
Q

What is the most common dermatophyte infection?

A

Tinea Pedis

41
Q

Tinea Pedis Pathogenesis

A

• Begins as weeping, peeling lesion between 4th and 5th toes. May extend to other toes
• In toe webs, scaling, fissuring, maceration,
and erythema may be associated with an itching or burning sensation

42
Q

What are the most common species causing Tinea Pedis?

A

T. rubrum, T. mentagrophytes, E. floccosum

43
Q

What are the most common species causing Tinea Capitis?

A

T. tonsurans

44
Q

Pathogenesis of Dermatophytes

A
  • Inoculation via minor trauma
  • Penetrates stratum corneum and proliferates
  • Infection spreads laterally, not deeper
  • Spread to other keratinized structures
45
Q

How are dermatophytes diagnosed?

A

• Direct exam of leading edge of skin lesion by KOH or calcofluor
• Examine hair under Wood’s light
– Damaged hair fluoresces
– Remove infected hair at shaft for culture
• Culture to rule out other pathogens

Pathology (203 decks)

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