Mycology I Flashcards Preview

Pathology > Mycology I > Flashcards

Flashcards in Mycology I Deck (45):
1

What is the cell wall of fungi made of?

Chitin

2

What is the predominant sterol in fungi?

Ergosterol

3

Hyphae

There are a long, branching filamentous structure

4

Germ Tube

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.

5

Pseudohyphae

Sausage linked looking hyphae that from from a germ tube

6

Conidia

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

7

Arthroconidia

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

8

Phialide

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

9

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

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

"Yeast in the heat, mold in the cold"

10

What is the most common opportunistic fungal pathogen?

Candida

11

Where is Candida found?

Normal flora of GI and GU tracts

12

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

C. albicans and C. dubliensis

13

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

C. dubliniensis

14

What Candida is resistant to fluconazole?

C. glabrata

15

What in Candida activates the complement system?

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

16

What are the risks for Candida infection?

• Antibiotic therapy
• Corticosteroid use
• Decreased T cell function
• Diabetes

17

What types of Candida albicans infection can be seen?

- Mucocutaneous
- Skin and nail
- Vulvovaginal
- Urinary tract infection
- Meningitis
- Endophthalmitis

18

What are the stains for C. albicans?

- Gram stain
- Calcofluor stain

19

What are the spores typically produced by C. albicans?

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

20

What are the characteristics of aspergillum?

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

21

What is the angle of branching in Aspergillus?

45˚

22

What is the most important Aspergillus species?

A. fumigatus

23

What is the pathogenesis of A. fumigatus?

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

24

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

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

25

What are the 2 families of fungi that cause murcomycosis?

Mucoraceae and Cunninghamellacea

26

Where are the agents of murcomycosis found?

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

27

What type of patients does murcomycosis typically occur in?

Immunocompromised

28

What species is most commonly associated with murcomycosis?

Rhizopus arrhizus

29

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

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

Who is at risk for Rhizopus infection?

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

31

What are some risk factors for Rhizopus infection?

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

32

Rhinocerebral mucormycosis

– 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

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

Early diagnosis

34

What is the branching angle seen in murcomycosis?

90˚

35

What are the diagnostic features of murcomycosis?

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

36

Dermatophytosis

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

37

What are the 3 genera of dermatophytes?

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

38

What does "ringworm" refer to in dermatophytosis?

• 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

Tinea Pedis

Athlete's Foot

40

What is the most common dermatophyte infection?

Tinea Pedis

41

Tinea Pedis Pathogenesis

• 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

What are the most common species causing Tinea Pedis?

T. rubrum, T. mentagrophytes, E. floccosum

43

What are the most common species causing Tinea Capitis?

T. tonsurans

44

Pathogenesis of Dermatophytes

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

45

How are dermatophytes diagnosed?

• 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

Decks in Pathology Class (203):