Diagnostic Mycology PART 1 Flashcards
Characteristic Features of Fungi Seen in Direct Examination of Clinical Specimens: Morphologic Form Found in Specimens
- Yeastlike
- Spherules
- Yeast and pseudohyphae or hyphae
- Pauciseptate hyphae
- Hyaline septate hyphae
- Dematiaceous septate hyphae
- Sclerotic bodies
- Granules
Yeastlike fungi:
1.Histoplasma capsulatum (2-5)
2.Sporothrix spp. (2-6)
3.Cryptococcus spp. (2-15)
4.Malassezia furfur (infungemia) (1.5-4.5 )
5.Blastomyces spp. (8-15)
6.Paracoccidioides brasiliensis (5-60)
Small; oval to round budding cells;
often found CLUSTERED IN HISTIOCYTES;
difficult to detect when present in small
numbers
Histoplasma capsulatum
Small; oval to round to CIGAR SHAPED
single or multiple buds present;
uncommonly seen in clinical specimens
Sporothrix spp.
Cells exhibit great variation in size;
usually spherical but may be FOOTBALL SHAPED ; buds single or multiple and “pinched off”; capsule may or may not be evident;
occasionally, pseudohyphal forms with or
without a capsule may be seen in
exudates of cerebrospinal fluid
Cryptococcus spp.
Small; BOTTLE SHAPED cells, buds separated
from parent cell by a septum;
emerge from a small collar.
Malassezia furfur (in fungemia)
Cells are usually large, DOUBLE REFRACTILE
when present; buds usually single;
however, several may remain attached to
parent cells; buds connected by a BROAD BASE
Blastomyces spp.
Cells are usually large and are surrounded
by smaller buds around the periphery
(“mariner’s wheel appearance”); smaller
cells may be present (2-5 µm) and
resemble H. capsulatum; buds have
“pinched-off” appearance
Paracoccidioides brasiliensis
Spherules Fungi:
- Coccidioides spp. 10-100
- Rhinosporidium seeberi 6-300 (protozoan pathogen that is studied in
mycology)
Vary in size; some may contain
endospores, others may be empty;
adjacent ____may resemble
Blastomyces spp.; endospores may
resemble H. capsulatum but show no
evidence of budding; may
produce multiple germ tubes if a direct
preparation is kept in a moist chamber
greater than/equal to 24 hr
Coccidioides spp.
Large, thick-walled sporangia containing
sporangiospores are present;
mature sporangia are LARGER THAN
spherules of Coccidioides;
hyphae may be found in cavitary lesions.
Rhinosporidium seeberi
Yeast and pseudohyphae or hyphae fungi:
- Candida spp. except Candida glabrata 5-10
- M. furfur (in tinea versicolor) 3-8 (yeast)
2.5-4 (hyphae)
Cells usually exhibit single budding;
pseudohyphae, when present, are
constricted at the ends and remain
attached like links of sausage; hyphae,
when present, are septate.
Candida spp. except Candida glabrata
Short, curved hyphal elements are usually
present, along with round yeast cells that
retain their spherical shape in compacted
clusters; “spaghetti and meatballs.
M. furfur (in tinea versicolor)
Pauciseptate hyphae Fungi:
Mucorales: Mucor,Rhizopus, and other
genera 10-30
Hyphae are large, ribbonlike, often
fractured or twisted; occasional septa may
be present; smaller hyphae are confused with those of Aspergillus spp., particularly Aspergillus flavus
Mucorales: Mucor, Rhizopus, and other
genera
Hyaline septate hyphae Fungi:
- Dermatophytes, skin and nails 3-15
- Dermatophytes, hair 3-15
- Aspergillus spp 3-12
- Geotrichum spp. 4-12
- Trichosporon spp. 1-4 by 8
Hyaline, septate hyphae are commonly
seen; chains of arthroconidia may be present.
Dermatophytes, skin and nails
Arthroconidia on periphery of hair shaft
producing a sheath indicate ectothrix
infection; arthroconidia formed by
fragmentation of hyphae in the hair shaft
indicate endothrix infection.
Long hyphal filaments or channels in the
hair shaft indicate favus hair infection
Dermatophytes, hair
Hyphae are septate and exhibit
dichotomous, 45-degree branching; larger
hyphae, often disturbed, may resemble
those of Mucorales
Aspergillus spp.
Hyphae and rectangular arthroconidia are
present and sometimes rounded; irregular
forms may be present.
Geotrichum spp.
Hyphae and rectangular arthroconidia are
present and sometimes rounded;
occasionally, blastoconidia may be
present.
Trichosporon spp.
Dematiaceous septate hyphae fungi:
1.Bipolaris spp.,
2.Cladosporium spp.,
3.Curvularia spp.,
4.Exophiala spp.,
5.Exserohilum spp.,
6.Hortaea werneckii,
7.Phialophora spp
Dematiaceous polymorphous hyphae are
seen; budding cells with single septa and
chains of swollen rounded cells are often
present; occasionally, aggregates may be
present in infection caused by
BEECCH Phia 2-6
1.Bipolaris spp.,
2.Cladosporium spp.,
3.Curvularia spp.,
4.Exophiala spp.,
5.Exserohilum spp.,
6.Hortaea werneckii,
7.Phialophora spp
Sclerotic bodies Fungi:
1.Cladosporium carrionii
2.Fonsecaea compacta
3.Fonsecaea pedrosoi
4.Phialophora verrucosa
5.Rhinocladiella aquaspersa
White, soft granules without a
cementlike matrix. 200-300
Acremonium
2.Acremonium falciforme
3.Acremonium kiliense
4.Acremonium recifei
Brown, round to pleomorphic,
thick-walled cells with transverse
septations; commonly, cells contain two
fission planes that form a tetrad of cells
sclerotic bodies
(5-20)
1.Cladosporium carrionii
2.Fonsecaea compacta
3.Fonsecaea pedrosoi
4.Phialophora verrucosa
5.Rhinocladiella aquaspersa
Black, hard grains with a cementlike
matrix at the periphery
Aspergillus 500-1000
-Aspergillus nidulans
White, soft granule without a cementlike
matrix. 65-160 dm/mm
Curvularia
-Curvularia geniculata
-Curvularia lunata
Black, soft granules, vacuolated,
without a cementlike matrix, made of
dark hyphae and swollen cells.
Exophiala 200-300
-Exophiala jeanselmei
White, soft granules without a
cementlike matrix 200-500
Fusarium
-Fusarium moniliforme
300-600 size range granule
Fusarium solani
Black, soft granules without a
cementlike matrix; the periphery is
composed of polygonal swollen cells
and the center has a hyphal network
Madurella 350-500
-Madurella grisea
Black to brown, hard granules;
two types:
(1) rust-brown, compact, filled with
cement-like matrix;
(2) deep brown, filled with numerous
vesicles, 6-14 µm in diameter,
cementlike matrix in periphery, central
area of light-colored hyphae.
Madurella mycetomatis 200-900
White, soft granules with cementlike
matrix at the periphery. 300-600
Neotestudina
-Neotestudina rosatii
White, soft granules composed of
hyphae and swollen cells at the
periphery in a cementlike matrix.
Pseudallescheria 200-300
-Pseudallescheria boydii
fungal infections that involve hair, skin, or nails without direct invasion of deeper tissue
Superficial (cutaneous) mycoses
Infections that are confined to the subcutaneous tissue without dissemination to distant sites
Subcutaneous mycoses
Four categories of mycoses according to the type of infection:
Superficial (cutaneous) mycoses
Subcutaneous mycoses
Systemic mycoses
Opportunistic mycoses
Affects the skin and hair epidermis
Superficial Mycoses
Affects the skin and nail
Cutaneous Mycoses
Affects the subcutaneous tissues
subcutaneous mycoses
Affects organs
Systemic or deep mycoses
usually occur in immunocompetent hosts, are not always as virulent, and may lead to
subclinical disease.
primary pathogens
Infect immunocompromised hosts. Opportunistic pathogens include almost any fungus present in the environment
Opportunistic pathogens
Virulence factors:
1.The organism’s size (with inhalation, the organism must be small enough to reach the alveoli)
2.The organism’s ability to grow at 37°C at a neutral pH
3. Conversion of the dimorphic fungi from the mycelial form into the corresponding yeast or spherule form in the host
4.Toxin production
most common specimens collected for fungal culture
Respiratory Tract Secretions
For optimal recovery of fungi, media without antibiotic and a media containing antibacterial antibiotics should be used to prevent
overgrowth of contaminants
Respiratory Tract Secretions
antifungal agent cycloheximide prevents overgrowth by rapidly growing molds and should be included in at least one of the culture media
Respiratory Tract Secretions
Specimens may be stored at room temperature if processing is completed
within 2 hours; if processing is delayed, specimens should be refrigerated
at 4°C
Respiratory Tract Secretions
centrifuged and the concentrated sediment used to inoculate the culture medium; cultures should be examined daily
Cerebrospinal Fluid (CSF)
< 1 mL spx submitted for culture:
Cerebrospinal Fluid (CSF)
centrifuged, 1-drop aliquots of the sediment should be placed on several areas on the agar surface
Cerebrospinal Fluid (CSF)
should be processed promptly. If prompt processing is not possible, samples should be kept at room temperature or placed in a 30°C incubator, specimens should NEVER be refrigerated.
Cerebrospinal Fluid (CSF)
provide an accurate method for determining the cause in many instances of disseminated fungal infections
Blood
placed directly onto microscopic slides and
inoculated onto non inhibitory media in either a X- or C-shaped pattern.
Corneal scrapings
concentrated by centrifugation and the
sediment should be used for smears and culture.
Vitreous humor aspiration:
Media containing cycloheximide should be avoided to prevent inhibition of potential isolates
Eye (Corneal Scrapings or Vitreous Humor)
Samples collected from lesions may be obtained by scraping the skin or nails with a scalpel blade or microscope slide; infected hairs are removed by plucking them with forceps.
Hair, Skin, and Nail Scrapings
Only the _____should be sampled, because the
centers often contain non viable organisms
leading edge of skin lesions
Hair, Skin, and Nail Scrapings Specimens should be placed in a sterile container; they should not be
refrigerated
Hair, Skin, and Nail Scrapings Cultures should be incubated
minimum of 21 days at 30°C before
being reported as negative.
should be transported to the laboratory within 24 hours of collection using culture transport swabs; swabs should be kept moist in sterile
tubes
Vaginal
Vaginal cultures should be
screened for yeasts and incubated at 30°C for 7 days
Urine samples collected for fungal culture should be processed as soon after collection as possible; 24-hour urine sample is
unacceptable for culture
All urine samples should be centrifuged and the sediment cultured using a____to provide adequate isolation of colonies.
loop
Because urine often is contaminated with gram-negative bacteria, media containing ____ must be used to ensure the recovery of fungi.
antibacterial agents
If urine processing is completed within 2 hours, samples may remain at room temperature, if processing is delayed,
specimens should be refrigerated at 4°C
If a urine transport system is used, samples may be stored at room temperature for up to ?
72 hours
All tissues should be processed before culturing by ___; not grinding is critical
mincing
Tissue pieces should be pressed into the appropriate culture media so that they are partially embedded, and the cultures should be incubated
at 30°C for 21 days (incubation may be extended if clinical suspicion of
a mycotic disease is high)
Bone marrow may be collected in a
heparinized syringe.
Tissue, Bone Marrow, and Sterile Body Fluids
The sample should be placed directly onto the surface of appropriate culture media
and incubated at
30°C for 21 days
should be concentrated by centrifugation before culturing, and at least 1 mL of specimen should be placed on the surface of appropriate culture media
Sterile body fluids
TRUE OR FALSE
All specimens should be cultured as soon as possible to ensure the recovery of fungi.
TRUE
are satisfactory for the recovery of fungi;
Agar plates or screw-capped agar tubes
preferred, because they provide better aeration of cultures, a large surface area for better isolation of colonies, and greater ease of handling
plates
TRUE OR FALSE
Dishes should be opened and examined in a certified biological safety cabinet (BSC)
TRUE
are used, the tube should be as large as possible to provide an adequate surface area for isolation.
culture tubes
After inoculation, tubes should be placed in a _____for at least ___ to allow the specimen to absorb to the agar surface and
prevent settling at the bottom of the tube.
horizontal position
1 to 2 hours
Cotton-plugged tubes are unsatisfactory for fungal cultures.
TRUE
Cultures should be incubated at______ days before they are reported as negative
room temperature, or preferably at 30°C,
for 21 to 30 days
Addition of 0.5 mg/mL of cycloheximide and 16 mg/mL of chloramphenicol to media has been advocated to inhibit the growth of contaminating molds and bacteria, respectively.
TRUE
better results have been achieved using a combination of _____as antibacterial agents. Ciprofloxacin at a concentration of 5 mg/mL may be used.
5 mg/mL of gentamicin and 16 mg/mL of chloramphenicol
