Mycology Flashcards
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
Q
How do you diagnose Aspergillosis?
A
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
Q
Aspergillus size in tissue?
A
Aspergillus hyphae in tissue are 5-10 µm in diameter
27
Q
What is it?
A
Zygomycetes in Culture
- Wooly, rapidly growing mold
- Large, distinctive sporangium
28
Q
Mucormycosis (formerly Zygomycosis) Microbiology
- Pathogenic species?
- Common properties?
A
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
Q
Mucormycosis
Where is it found?
6 major risk factors?
A
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
Q
Mucormycosis 4 sites of involvement?
A
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
Q
How do you diagnose Mucormycosis?
A
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
Q
Mucormycosis size in tissue?
A
Mucormycosis hyphae in tissue are 10-30 µm in diameter
33
Q
How do you treat Mucormycosis?
A
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
Q
What is it?
Risk factor?
Common site of infection?
A
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
Q
Dermatophyte infections
3 major genera?
A
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
Q
What is it?
A
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
Q
What is it?
A
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
Q
What is it?
A
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
Q
Differences between Dermatophytes?
A
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
Q
What is it?
A
Candida albicans
- Budding spherical to ovoid blastoconidia
41
Q
What is it?
A
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
Q
What is it?
A
Candida glabrata
- No pseudohyphae – also seen with Cryptococcus , but capsule usually evident as space surrounding cell for Crypto
- Frequently fluconazole resistant
43
Q
What is it?
A
Candida parapsilosis
- Short, curving pseudohyphae with round to oval blastoconidia
44
Q
What is it?
A
Candida tropicalis
- Multibranched pseudohyphae, blastoconidia borne singly or in chains from along pseudohyphae
45
Q
What is it?
A
Candida lusitaniae
- Short, curved pseudohyphae with blastoconidia at or between septae.
- Tends to develop Amphotericin B resistance
46
Q
What is it?
A
Candida krusei
- Branching pseudohyphae with elongated blastoconidia.
- Inherently resistant to fluconazole, but typically susceptible to voriconazole and posaconazole
47
Q
Candidiasis Treatment
- C. glabrata and C. krusei are resistant to ____
- C. lusitaniae is resistant to _____
A
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
Q
What is it?
What are the tests?
A
Cryptococcus - Biochemicals
- Produces melanin on Birdseed Agar
- Strongly urease positive
49
Q
Cryptococcosis ___ vs ____
Media?
A
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
Q
Cryptococcosis Epidemiology/ecology
- Where in the world?
- C. ____ a/w ____ droppings
- C. ____ a/w ____ trees in ____
- Current epidemic?
- __% a/w abnormal ____ immunity
A
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
Q
What is it?
Media?
A
Crypto on cornmeal agar
52
Q
A
Crypto histology
53
Q
Stains?
Size?
A
Crypto stains
5-10 microns
54
Q
Diagnosis?
Associate with?
Symptoms?
Diagnosis?
Treatment?
A
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
Q
A
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.
