Mycology Flashcards
(55 cards)
1
Q
Basic characteristics of fungi
- Eukaryotic/Prokaryotic?
- Energy and nutrition?
- Reproduce?
- Cell walls made of?
- Principal cell wall sterol?
- How do they grow?
A
Basic characteristics of fungi
- Eukaryotic (membrane-bound nucleus, complex organelles)
- Energy and nutrition - parasitic or saprophytic.
- Reproduce by budding, fission or spore formation
- Cell walls (polysaccharide and glycoproteins).
- Principal cell wall sterol is ergosterol
- Can grow as yeast-like cells or as molds
2
Q
Traditional Classification (4)
A
Traditional Classification
- Mucormycetes ( Rhizopus , Mucor , Absidia , Basidiobolus )
- Ascomycetes ( Histoplasma , Blastomyces , some Candida )
- Basidiomycetes ( Cryptococcus )
- Deuteromycetes (most pathogenic Candida species, pathogenic Aspergillus species, Coccidioides )
3
Q
Morphologic Classification (3)
A
Morphologic Classification
- Yeast
- grows as single cells
- Candida , Cryptococcus
- Molds
- Multicellular filaments (hyphae), multiple genetically identicle nuclei, colony
- Aspergillus, Mucormycetes, many others
- Dimorphic fungi
- yeasts/spherules at 37°C, molds at 25°C
- Histoplasma, Blastomyces, Coccidioides, Paracoccidioides, Sporothrix
4
Q
Diagnosis of Fungal Diseases
A
Diagnosis of Fungal Diseases
- Culture causative fungus.
- Microscopic morphology
- Demonstrate specific host immune response
- Demonstrate fungal antigen(s)
- Demonstrate fungal nucleic acid sequence(s)
- Demonstrate distinctive fungal metabolite(s)
5
Q
How do you culture fungi?
A
Culture
- Yeast-like fungi ( Candida spp. and related)
- grow on routine bacterial media
- Filamentous fungi (molds)
- may grow on routine media
- should be cultured on mycologic media for optimum recovery
- special requirements ( M. furfur )
6
Q
Mycologic Media (6)
A
Mycologic Media
- Culture media for primary isolation): selective & non-selective agars, that can include:
- Sabouraud’s glucose agar (SAB), non-selective
- Selective SAB, with chloramphenicol
- Selective SAB, with chloramphenicol plus cycloheximide (Actidione)
- Blood Brain Heart Infusion (BBHI), non-selective
- BBHI with gentamicin (G) & chloramphenicol (C)
- Selective BBHI with G, C & Actidione
- Usually incubated at 30oC
- For possible dimorphs sub at 37 to convert to yeast
7
Q
Fungal Identification
A
Fungal Identification
- Yeasts: biochemical, supplemented by morphology
- Molds and dimorphs: morphology, supplemented by biochemical and sequencing
- MALDI-TOF is becoming widely used for yeasts; very promising for the rest.
8
Q
Can We Do Fungal Blood Cultures?
A
Can We Do Fungal Blood Cultures?
- Yes!
- 90% of the time looking for yeast fungemia; usually from a urinary source
- Conventional blood culture is perfectly adequate
- Some conventional systems are insensitive for Cryptococcus
- Occasionally looking for fungemia with a mold or dimorph; Aspergillus, Fusarium, Histoplasma
- Special culture procedures
- Biphasic bottle
- Lysis-centrifugation (Isolator) system
9
Q
Can you see fungi on Gram stains?
A
Microscopy
- Budding yeast or mycelia are often evident on Gram stains
10
Q
Diagnostically-useful fungal antigens
A
Diagnostically-useful fungal antigens
- Commonly Used
- Cryptococcus neoformans galactoxylomannan
- Histoplasma capsulatum surface antigens
- Used in specific/complex situations
- Candida albicans enolase
- Aspergillus fumigatus galactomannan
11
Q
5 Types of Antifungal Drugs?
A
Antifungal Drugs
- The azoles
- The echinocandins
- Amphotericin and derivatives
- Flucytosine
- Griseofulvin & Terbinafine
12
Q
Antifungal Drugs
- The azoles
A
Antifungal Drugs
- The azoles
- Ketoconazole: rarely used
- Fluconazole: low toxicity, active against Cryptococcus , C. albicans , selected other Candida
- Itraconazole: unreliable absorption, broad spectrum, esp vs dermatophytes
- Posaconazole: oral only, broad spectrum; some anti-Zygomycete activity
- Voriconazole: oral or IV, broad specturm, highly effective vs Aspergillus .
13
Q
Antifungal Drugs
- The echinocandins
A
Antifungal Drugs
- The echinocandins
- Expensive
- very complete Candida coverage
- good vs Aspergillus
- limited coverage vs other fungi
- Often used as second-line / salvage therapy.
- Caspofungin, anidulafungin, micafungin, all IV only.
- NO activity vs Cryptococcus.
14
Q
Antifungal Drugs
- Amphotericin and derivatives
A
Antifungal Drugs
- Amphotericin and derivatives
- Covers most Candida , Aspergillus , dimorphics with some specific exceptions.
- IV only.
- Nephrotoxic and infusion-related toxicities
- liposomal and similar derivatives better tolerated.
15
Q
Antifungal Drugs
- Flucytosine
- Griseofulvin & Terbinafine
A
Antifungal Drugs
- Flucytosine: effective adjunctive agent vs Cryptococcus .
- Griseofulvin & Terbinafine: good activity vs. dermatophytes.
16
Q
Mold anatomy
A
Aspergillus
17
Q
Aspergillosis
- Yeast/Mold/Dimorph?
- 3 Pathogenic species?
- Common features?
A
Aspergillosis
- Mold
- Pathogenic species
- A. fumigatus
- A. flavus
- A. niger
- Common features
- narrow septate hyphae that branch at 30-45o in tissue (acute-angle branching)
- produce asexual spores in environment and in cultures, but not in mammalian tissues
18
Q
What is it?
A
Aspergillus fumigatus
- The most common pathogen
- A. fumigatus has a dark-green colony
- Flask-shaped vesicle with conidia swept away from stalk
- Single row of phialides (uniseriate)
19
Q
What is it?
A
Aspergillus flavus
- Biseriate (2 rows of phialides)
- Yellow colony
- Phialides surround vesicle
20
Q
What is it?
A
Aspergillus niger
- White base with densely black conidia
- Dark, rough conidia
21
Q
Risks for Aspergillosis?
A
Aspergillosis: Epidemiology/ecology
- Ubiquitous environmental saprophytes (dust, soil, on plants, etc).
- Everyone is exposed to spores every day.
- Neutropenia or phagocyte dysfunction (eg, CGD) is the key risk factor for invasive aspergillosis.
- T-cell immunity is less important.
- Environment influences incidence
- decreases with filtered air
- increased with construction/demolition
22
Q
Aspergillosis Allergic Bronchopulmonary Disease
3 types?
A
Aspergillosis Allergic Bronchopulmonary Disease
- hypersensitivity –> allergic pneumonitis or allergic bronchopulmonary aspergillosis (ABPA)
- allergic aspergillosis
- bronchospasm
- fleeting pulmonary infiltrates
- tends to be chronic or recurrent
- refractory asthma
23
Q
Aspergillosis Pulmonary colonization
Risks?
Symptoms?
A
Aspergillosis Pulmonary colonization
- saprophytic colonization
- usually no symptoms, but hemoptysis can result from local invasion
- saprophytic colonization of preexisting lung lesions
- superficial invasion
- hemoptysis
24
Q
Invasive Aspergillosis
A
Invasive Aspergillosis
- Invasive aspergillosis:
- infection via inhalation of airborne spores
- spores survive and germinate (produce hyphae) if local phagocytes are absent or dysfunctional
- hyphae invade locally and spread via blood vessels
- dissemination to distant organs via bloodstream
- vascular invasion and occlusion produces extensive tissue necrosis and infarction
- Pulmonary
- Sinusitis
- Other and disseminated disease
25
How do you diagnose Aspergillosis?
Aspergillosis Diagnosis
* Cultures
* blood negative, even with disseminated
* sputum/respiratory - colonization vs invasion
* Biopsy & microscopy - KOH of fresh tissue or histopathology
* Antibody testing seldom useful
* Immunologic detection of cell surface antigens
* Galactomannan test becoming more available,
* PCR of rDNA sequences in blood and/or bronchial fluids
* MORPHOLOGY
26
Aspergillus size in tissue?
Aspergillus hyphae in tissue are 5-10 µm in diameter
27
What is it?
Zygomycetes in Culture
* Wooly, rapidly growing mold
* Large, distinctive sporangium
28
Mucormycosis (formerly Zygomycosis) Microbiology
* Pathogenic species?
* Common properties?
Mucormycosis (formerly Zygomycosis) Microbiology
* Pathogenic species - Mucormycetes
* Rhizopus sp.
* Mucor sp.
* Absidia sp.
* Common properties
* broad, aseptate hyphae, branching at 90o in tissue
* produce sexual and asexual spores in the environment and in cultures, but not in mammalian tissues
29
Mucormycosis
Where is it found?
6 major risk factors?
Mucormycosis Epidemiology/ecology
* Ubiquitous environmental molds (decaying organic matter, fruits, etc)
* Major risk factors include:
* diabetic ketoacidosis
* other metabolic acidoses (eg, uremia)
* organ transplantation and abnormal CMI
* neutropenia
* burns
* iron chelation therapy
30
Mucormycosis 4 sites of involvement?
Mucormycosis
* Rhinocerebral
* Pulmonary
* necrotizing pneumonitis with secondary blood vessel invasion, thrombosis & infarction
* Dissemination to distant organs is common
* Cutaneous
* complication of extensive burns or other wounds
* Gastrointestinal (rare)
* invasion of gastrointestinal mucosa in malnourished children in developing countries
31
How do you diagnose Mucormycosis?
Mucormycosis - Diagnosis
* Cultures often negative, even in specimens containing visible fungal forms
* Direct microscopy (KOH preps or histology) is most important diagnostic modality
* No reliable serologic tests for antibodies or antigens, no DNA tests at this time.
32
Mucormycosis size in tissue?
Mucormycosis hyphae in tissue are 10-30 µm in diameter
33
How do you treat Mucormycosis?
Mucormycosis - Treatment
* Multiple treatment modalities are essential
* correct underlying host defense abnormality
* surgical debridement/removal of necrotic tissues is essential
* amphotericin B
* posaconazole has some activity
* Isavuconazonium approved specifically for Mucorales in 2015
34
What is it?
Risk factor?
Common site of infection?
Fusarium
* Opportunistic pathogen, esp in neutropenic patients
* Common in fungal keratitis
* Most commonly F. solani complex
* Fusiform macroconidia; microconidia produced as well
* Fluffy, white or colored colonies in culture
35
Dermatophyte infections
3 major genera?
Dermatophyte infections
* Taenia whatever…
* Capitis; head and hair
* Corporis, cruris, pedis; skin of body, groin, or feet
* Onychomycosis – nail infections
* Three major genera
* Trichophyton
* Epidermophyton
* Microsporum
36
What is it?
Trichophyton
* Colonies
* Slow to moderately rapid growth
* Waxy, glabrous to cottony
* Front, white to bright yellowish beige or red violet
* Reverse pale, yellowish, brown, or reddish-brown
* Microscopic
* Microconidia, macroconidia, and arthroconidia
* Miroconidia numerous; onecelled and round or pyriform in shape.
* Macroconidia are multicellular smooth-walled and cylindrical, clavate or cigar-shaped. Produced in very few numbers or not at all.
37
What is it?
Microsporum
* Colonies
* Glabrous, downy, wooly or powdery
* Growth variable
* Color varies depending on the species
* Front: white to beige or yellow to cinnamon.
* Reverse: yellow to red-brown.
* Microconidia
* Unicellular, solitary, oval to clavate in shape, smooth, hyaline and thin-walled.
* Macroconidia
* hyaline, echinulate to roughened, thin- to thickwalled, typically fusiform and multicellular, often with an annular frill.
38
What is it?
Epidermophyton
* Colonies
* Grow moderately rapidly (10d or so)
* Front: brownish yellow to olive gray or khaki
* Reverse: orange to brown with an occasional yellow border.
* Flat and grainy initially; then radially grooved and velvety.
* Microconidia are typically absent.
* Macroconidia (10-40 x 6-12 µm), thin walled, 3- to 5- celled, smooth, and clavate-shaped with rounded ends
39
Differences between Dermatophytes?
The Dermatophytes Compared
* Trichophyton differs from Microsporum and Epidermophyton by having cylindrical, clavate to cigar-shaped, thin-walled or thick-walled, smooth macroconidia.
* Epidermophyton is differentiated from Microsporum and Trichophyton by the absence of microconidia.
* Microsporum differs from Trichophyton and Epidermophyton by having spindle-shaped macroconidia with echinulate to rough walls
40
What is it?
Candida albicans
* Budding spherical to ovoid blastoconidia
41
What is it?
Candida dubliniensis
* Morphologically identical to C. albicans
* Germ-tube positive
* More likely to develop fluconazole resistance
* Distinguish by:
* C. albicans growth at 45oC
* C. dubliniensis dark-green colonies on Chromagar
* C. dubliniensis reduction of 2,3,5-triphenyltetrazolium chloride
* Molecular methods (other methods not entirely accurate)
42
What is it?
Candida glabrata
* No pseudohyphae – also seen with Cryptococcus , but capsule usually evident as space surrounding cell for Crypto
* Frequently fluconazole resistant
43
What is it?
Candida parapsilosis
* Short, curving pseudohyphae with round to oval blastoconidia
44
What is it?
Candida tropicalis
* Multibranched pseudohyphae, blastoconidia borne singly or in chains from along pseudohyphae
45
What is it?
Candida lusitaniae
* Short, curved pseudohyphae with blastoconidia at or between septae.
* Tends to develop Amphotericin B resistance
46
What is it?
Candida krusei
* Branching pseudohyphae with elongated blastoconidia.
* Inherently resistant to fluconazole, but typically susceptible to voriconazole and posaconazole
47
Candidiasis Treatment
* C. glabrata and C. krusei are resistant to \_\_\_\_
* C. lusitaniae is resistant to \_\_\_\_\_
Candidiasis Treatment
* azoles (fluconazole, voriconazole, posaconazole)
* Resistance to fluconazole in C. glabrata and C. krusei
* Some Candida species resistant to specific antifungals
* C. lusitaniae & Ampho B
48
What is it?
What are the tests?
Cryptococcus - Biochemicals
* Produces melanin on Birdseed Agar
* Strongly urease positive
49
Cryptococcosis ___ vs \_\_\_\_
Media?
Cryptococcosis gattii vs neoformans
* Canavanine glycine bromthymol blue agar (CGB agar) can be used to distinguish between C. gattii and C. neoformans .
* C. gattii is blue on this medium.
* Requires genotyping for confirmation.
50
Cryptococcosis Epidemiology/ecology
* Where in the world?
* C. ____ a/w ____ droppings
* C. ____ a/w ____ trees in \_\_\_\_
* Current epidemic?
* \_\_% a/w abnormal ____ immunity
Cryptococcosis Epidemiology/ecology
* worldwide distribution
* var. neoformans associated with pigeon droppings and soil.
* var. gattii associated with Eucalyptus trees in Australia and Southern California; current epidemic evolving in British Columbia and Pacific Northwest
* \>80% of infections in people with serious abnormalities of cell-mediated immunity (eg, AIDS, transplantation, others).
51
What is it?
Media?
Crypto on cornmeal agar
52
Crypto histology
53
Stains?
Size?
Crypto stains
5-10 microns
54
Diagnosis?
Associate with?
Symptoms?
Diagnosis?
Treatment?
Malasessia furfur = Spagetti and Meatballs
* lipophilic yeast
* associated with catherter infections
* neonates on extended courses of parenteral lipid.
* adults with severe immunocompromise
* Fever, signs of sepsis, catheter blockage.
* Diagnosis requires lipid in culture; alert lab
* Treated by catheter removal and D/C lipids if possible.
55
Sporotrichosis Microbiology & Epidemiology
Sporothrix schenckii
* dimorphic (hyphae at ambient temp, round to cigar-shaped yeast at 37oC and in tissues
* natural habitat: soil and plant matter
* Worldwide distribution
* Most frequent in gardeners or others exposed to plant material.
