1. Coccidioides spp. 10-100 2. Rhinosporidium seeberi 6-300 (protozoan pathogen that is studied in mycology)

Diagnostic Mycology PART 1 Flashcards by Khienja Maverick Gonzaga

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

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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)

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Small; oval to round budding cells;
often found CLUSTERED IN HISTIOCYTES;
difficult to detect when present in small
numbers

Histoplasma capsulatum

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Small; oval to round to CIGAR SHAPED
single or multiple buds present;
uncommonly seen in clinical specimens

Sporothrix spp.

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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.

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Small; BOTTLE SHAPED cells, buds separated
from parent cell by a septum;
emerge from a small collar.

Malassezia furfur (in fungemia)

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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.

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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

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Spherules Fungi:

Coccidioides spp. 10-100
Rhinosporidium seeberi 6-300 (protozoan pathogen that is studied in
mycology)

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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.

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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

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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)

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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

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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)

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Pauciseptate hyphae Fungi:

Mucorales: Mucor,Rhizopus, and other
genera 10-30

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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

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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

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Hyaline, septate hyphae are commonly
seen; chains of arthroconidia may be present.

Dermatophytes, skin and nails

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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

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Hyphae are septate and exhibit
dichotomous, 45-degree branching; larger
hyphae, often disturbed, may resemble
those of Mucorales

Aspergillus spp.

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Hyphae and rectangular arthroconidia are
present and sometimes rounded; irregular
forms may be present.

Geotrichum spp.

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Hyphae and rectangular arthroconidia are
present and sometimes rounded;
occasionally, blastoconidia may be
present.

Trichosporon spp.

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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

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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

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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