Mycoses Flashcards
(102 cards)
0
Q
This group of fungi includes cryptococcus neoformans
A
Basidiomycota
1
Q
What is the largest group of fungi, which includes pathogens Aspergilllus and Candida. Sexual structures are asci, sacs of ascospores…
A
Ascomycota
2
Q
Most medically important fungi are (Non/Motile)
A
NON-MOTILE
3
Q
The main distinguishing factor of fugal cell membranes from humans is the presence of:
A
ERGOSTEROL
instead of cholesterol = good drug target
4
Q
Describe the cell wall of a fungus in 3 basic layers (outside to in)
A
- Outer dense glycoprotein layer
- Inner glucan layer (Chitin in bottom of this layer)
- Cytoplasmic membrane (contains ergosterol)
* polysaccharides account for 90% of a fungal cell wall mass *
5
Q
______________ is an important target of innate immunity to fungi
A
Beta 1,3 Glucan of the cell wall
6
Q
Anti-fungal therapy: What to AZOLES do?
A
target the fungal Cytochrome P450 Erg11A needed for ERGOSTEROL SYNTHESIS.
Drugs include: flucanazole, voriconazole
7
Q
Anti-fungal therapy: What do polyenes do?
A
Target ERGOSTEROL DIRECTLY
Drugs include: Amphotericin B, Natamycin A
8
Q
Anti-fungal therapy: What do Echinocandins do?
A
Target fungal BETA GLUCAN SYNTHESIS
Drugs: Caspofungin
9
Q
Amphoterecin B is fungi(cidal/static)
A
FungiCIDAL
10
Q
Nystatin is fungi(cidal/static)
A
FungiSTATIC
11
Q
T/F: Polyenes are poorly absorbed by the GI tract
A
True
12
Q
T/F: Amphotericin B CAN be used systemically
A
True, it is toxic but can be used systemically
13
Q
T/F: Nystatin CAN be used systemically
A
False, nystatin is too toxic and can only be used as a topical/oral agent. (‘swish and swallow’ is safe because polyenes are not absorbed by GI tract)
14
Q
T/F: Azoles CAN be used systemically
A
True, these are used for systemic mycoses.
They can cause hepatotoxicity in 0.01% of patients.
15
Q
Azoles are fungi(cidal/static)
A
Fungistatic; they inhibit ergosterol synthesis.
16
Q
Echinocandins are fungi(cidal/static)
A
FungiCIDAL; these inhibit 1,3 beta-D-glucan Synthase
17
Q
Flucytosine
Drug class?
Cidal/static?
A
The only ANTIMETABOLITE antifungal drug. Inhibits fungal protein synthesis by replacing uracil with 5-fluorouracil in fungal RNA.
It can be BOTH fungicidal and static, depending on the fungus.
18
Q
You have a fungus from a patient with a glucuronoxylomannan capsule. What is it??
A
Most likely Cryptococcus Neoformans.
This is the most common capsular fungus in medicine. Capsule may be found in urine, blood, CSF, etc.
19
Q
What is Sabouraud’s agar and why is it used
A
An agar with acidic pH; used for fungi because they are acid tolerant and it enriches their cultures.
20
Q
Aseptate or Coenocytic means:
A
Lack of Hyphae
21
Q
Define: Spitzenkorper
A
Collection of vesicles near the tip specific to hyphal growth
22
Q
What type of hyphal growth produces spores that are easily airborne?
A
Arial (as opposed to submerged, which is under the growth media)
23
Q
Dimorphism means
A
growth in 2 different forms - hyphal or yeast, depending on environment.
24
The most common fungal infections are ________ infections and are cause by _________
Skin infections
| Caused by Dematophytes
25
The dermatophytoses are caused by 3 fungal genera:
1. Epidermophyton
2. Trichophyton
3. Microsporum
26
Disease caused by dermatophytes are termed
Tinea (body part)
27
Fungi that infect hair from the outside are termed ______
| While those that infect hair from the inside are termed ________
Ectothrix
| Endothrix
28
Tinea Versicolor is caused by the organism ______
Malassezia Furfur
29
Clinical picture of Tinea Versicolor infection
Hypopigmented areas appear on skin.
| Is dimorphic in infected tissue
30
Tinea Nigra is caused by the organism __________
Cladosporium werneckii
31
Clinical picture of Tinea Nigra
Brown spots on skin cause by fungal melanin production.
Is dimorphic in infected tissue
32
How to diagnose Cutaneus fungal infection
KOH mount specimen
| Culture only for ID of specific macroconidia
33
What are microconidia?
| Macroconidia?
Microconidia are asexual spores that are small and airborne, often the infectious form of the fungus.
Marcoconidia are the large spores useful for identification
34
Subcutaneaus mycoses often come from fungi found __________
In soil or vegetation
35
Sporotrichosis:
Introduced by?
Clinical picture?
A subcutaneaus mycoses that is caused by sporothrix shenkii. It is introduced via puncture wound. Demonstrates classi dimorphism; budding yeast @ 37C and hyphae @ 25C.
Causes nodular lesions under skin from site of inoculation. Can disseminate if immunocompromised.
36
Chromoblastomycosis
Subcutaneaus mycoses that cause slow growing wart-like lesions with brown fungal cells.
37
Treatment for CUTANEOUS mycoses
Topical antifungal cream
| Tineas
38
Treatment for SUBcutaneous mycoses
Oral azole therapy. Surgery may be needed.
39
At room temperature, Candida albicans would appear as a ______ _________
Budding Yeast
40
At 37C, Candida appears as:
Producing germ tubes, which become vegetative hyphae in culture. Arial hyphae are NOT formed.
41
What part of the human body is colonized by Candida Albicans at birth?
The GI tract.
42
The source of most Candida infections is:
The patients own endogenous flora; person to person can also happen.
43
Which form of Candida Albicans is more adherent and invasive?
The Hyphal form (as opposed to the yeast form)
44
Which form of Candida Albicans is believed to promote escape from biofilms?
The yeast form.
45
What is a virulence 'property' of Candida Albicans
The ability to interconvert between the yeast and hyphal morphologies.
46
Those who suffer from chronic mucocutaneous candidiasis have a genetic deficiency in:
Th17 Cell immunity
47
What is the second most prevalent yeast pathogen after Candida albicans?
Candida Glabrata
48
Among Candidia Glabrata and Candida Albicans, which is most resistant to azoles?
C. Glabrata is MORE RESISTANT
49
Diagnosis of Candida
Culture! on blood or Sabauraud's agar = smooth white colonies after 2 days
50
Dectin-1
A host pattern recognition receptor that initiates immune response against fungi.
51
Th17 cells have been found to play a critical role in fungal immunity. What does IL-17 do?
IL-17, which is secreted by Th 17 cells, recruits NEUTROPHILS and activates epithelial cells to initiate anti fungal defences.
52
What stains would one use to visualize fungi histologically?
Periodic acid schiff
methanamine silver
GMS
53
Coccidioidomycosis is endemic in:
| Is more prevalent in:
Coccidioidomycosis is endemic in North, Central, and South America.
It is most prevalent among DARK SKINNED MEN
54
The two species that can cause coccidiomycosis (Valley Fever) are:
Coccidioides Immitis and Posadasii
55
Pathogenesis of coccidiomycosis:
1. Inhaled arthroconidia lodge in the alveoli -> form spherules in tissue
2. Rupture of spherule -> endospore release -> new spherule formation
3. Initial response by host macrophage and neutrophil; but spherules are resistant to neutrophil
56
T/F: Coccidiomycosis infection is often asymptomatic
True; 40% do have symptoms similar to lower resp. infection - cough, sputum, chest pain, malaise, fever, chills, anorexia, arthralgia.
57
How long does Valley Fever last?
2-6 weeks. (coccidiomycosis)
58
10% of coccidiomycosis patients may experience Erythema Nodosum (EN); what is EN and what does it indicate?
Erythema Nodosom is the formation of nodules that do not contain organisms. They are NOT indicative of disseminated disease, and INDICATE PROTECTIVE IMMUNITY
59
The onset of cell-mediated immunity to Coccidiomycosis may take _______ days/weeks/months and is indicated by:
2-4 weeks. This is indicated by use of a DTH skin test, which indicates protective immunity.
60
To diagnose coccidiomycosis:
detect spherules with KOH mount
Sarubouraud's Agar
IgM Ab @ 2-4 weeks
Caution - arthrospores are hazardous to lab techs!
61
Histoplasmosis is caused by what organism?
Histoplasma Capsulatum
62
T/F: Histoplasma Capsulatum produces a capsule
FALSE - No capsule. They may look capsular due to staining but they are not.
63
The tissue growth form (37C) of histoplasma capsulatum is:
Yeasts (ovoid, 1.5 - 2.0 micron)
64
Name one important virulence property of H. Capsulatum
Ability to grow within macropahges
65
Histoplasma capsulatum is highly endemic in ____ and ______
| Also is found in __________
Endemic in Ohio and Mississippi valley regions.
| Found in Bird shit.
66
Histoplasmosis Pathogenesis:
After spores are inhaled into bronchioles and alveoli....
- > germinate after 2-3 days
- > proliferate in macrophage
- > migrate to MEDIASTINAL LYMPH NODES
- > cell mediated response in 9-15 days
67
How do H. Capsulatum yeasts survive in marcopahges?
They increase the pH of phagolysosome by Bicarbonate and Ammonia production -> inactivates degradative enzymes.
68
T/F: most histoplasmosis infections are asymptomatic
True; acute pulmonary histoplasmosis is self-limiting in immunocompetent,, often unoticed
69
Chronic Pulmonary histoplasmosis is often mistaken for ______
and is opportunistic due to ______
Mistaken for TB
| Often opportunistic due to structural lung defects which allow colonization in abnormal lung spaces.
70
Your patient has Disseminated Histoplasmosis! What test should you perform that is (almost) always positive for intracellular yeasts within macrophages?
Wright stained smear of peripheral blood!
Also can use:
- Culture lung tissue organisms -> need to demonstrate dimorphism
- Histoplasma Ag urine test
- Serology
71
Why cant you use a skin test to confirm a H. Capsulatum infection?
Cross reactivity with Blastomyces Dermatitidis
72
You see 5 - 30 micron yeast with SINGLE BUDS and BROAD BASES and maybe a PEAR SHAPED CONIDIA in the mold form. You're lookin at:
Blastomyces Dermatitidis
73
Blastomycosis is a common infection in ______
Doggies
74
What is Bad1?
A surface protein on blastomyces dermatitidis required for virulence -> it PROMOTES UPTAKE BY MACROPHAGES where yeasts then multiply and are carried to other organs.
75
Blastomycosis has tissue tropism for ____ and _____
Skin and bone
76
Acute blastomycosis usually resolves spontaneously, but progressive disease can occur, involving:
The lungs + other organs. Often an influenza-like syndrome.
77
You see large yeasts at 37C with THICK WALLS, MULTIPLE BUDS, and WAGON WHEEL appearance; you are looking at:
Paracoccidioides Brasiliensis
| The cause of 'south american blastomycosis' - paracoccidioidomycosis
78
How to treat a sick dude with any systemic fungal infection
Probably do nothing, most resolve by themselves.
| If severe; Amphotericin B or azoles
79
A key distinguishing feature of cryptococci is:
A prominent polysaccharide capsule composed of glucuronoxylomannan (GXM). No capsule = No virulence.
SUGAR COATED KILLA
80
All pathogenic fungi are Urease (+/-) and grow at ____C
Urease +
| Grow at 37C
81
The disease caused by cryptococcus is:
Meningoencephalitis. Cryptococcci cause more life-threatening infection than any other fungus.
82
Cryptococcus Neoformans grows abundantly in ____
Soil with bird droppings
83
Cryptococcus gatti is found in the environment associated with
TREES...southwest canada
84
The most common route of infection for Cryptococcus is
Inhalation of spores
85
Cryptococcus has phenol oxidases which use ______ to make __________, which protects them from oxidative damage elicited by the host response.
Uses DOPAMINE to make MELANIN -> protection
86
The cryptococcus fungus has a preference for invading:
| It gets there by:
Preference for the CNS (meningoencephalitis)
| It gets there thru the micro capillaries of the BBB or by phagocyte delivery.
87
Diagnosis of C. Neoformans:
Capsular Ag in CSF
88
T/F: Aspergillus fumigatus and flavus exhibit classic dimorphism
FALSE; aspergillus grow in the myocelial (mold) form ONLY and are NOT DIMORPHIC
89
Mystery organism forms aerial hyphae in culture and in host tissue shows septate hyphae with V shaped branches...What is the mystery organism?
ASSPERGILLUS
90
Aspergillus is an endemic or opportunistic infection?
aspergillus is an opportunistic fungus - it occurs in immunsupressed
91
A common finding of aspergillosis after trauma or TB is the development of:
Aspergillomas, fungal balls
92
The best way to diagnose aspergillosis is
Galactomannan ELISA
93
organisms that form 'right-angle' branching in tissue and are not dimorphic are probably
mucormycoses/zygomycoses
94
Increased susceptibility to mucormycoses/zygomycoses might occur in:
Diabetic Ketoacidosis
95
The incidence of mucormycosis is increasing due to:
Prophylactic azole administration
96
T/F: Pneumocystis Carinii can be cultured on Saurbaraud's agar only
FALSE Pneumocystis CANNOT BE CULTURED ON ANYTHING EVER
97
Each form of pneumocystis has a 'specific form' for each animal it infects; what is the human form called?
Pneumocystis Carinii
98
```
Pneumocystis Carinii (jiroveci) is susceptible to:
It is NOT susceptible to:
```
Susceptible to antiparasitic drugs pentamidine and Trimethoprim sulfamethoxazole.
It is NOT susceptible to Amphotericin B
99
UNLIKE most fungi, P. Carinii has ______ in its cell membrane instead of the usual _______ that appears in fungal cell walls.
P. Carinii has CHOLESTEROL in the cell membrane; most other fungi have ERGOSTEROL
100
Pneumocystis pneumonia is often associated with early recognition of:
AIDS prior to the discovery of HIV
or
immunosuppressive therapies
101
Loss of ________ immunity (specificly) leads to pneumocystis pneumonia
CD4+ immunity.
transmission is thru aerosols.
