Mycology Flashcards
Fungal ball infection of the lung
Absidia spp.
Distinctive funnel-like expansion of the terminal conidiophore
4 day growth
Acremonium
Acremonium have long slender phialides that produce oval, unicellular microconidia that cluster at the tip of the phialide.
The clusters of microconidia are easily disrupted from the tip of the phialide.
Fungal conidia type
Aleurioconidia are formed from a newly formed hyphal branch which then separates from the main hypha by formation of a cross wall.
The porocondia of Alternaria are formed in chains and have a club-like shape.
Alternaria produces dematiaceous (dark), poroconidia with transverse and longitudinal septa (muriform).
Alternaria
Alternaria
Characterized by chains or groups of large dematiaceous (dark-colored), club shaped conidia. Many of the conidia show both transverse and longitudial segmenation.
Antifungal with ability to form pore in cell wall
Amphotericin B
Azole mechanism
Inhibition of cytochrome P-450 to block synthesis of ergosterol
Nucleic acid synthesis inhibitor used for cryptococcus meningitis
5-FC
Bone marrow toxicity and resistance can develop in days so always use in combination
Target of echinocandins
Block B-1,3-glucan synthase inhibitors
Echinocandins do not work on…
Zygomycetes
Fungal conidia type
Arthrocondia are formed by structural changes in the cell walls and septa of preformed hyphae. They are produced along the entire length of the hypha.
Product of diploid yeast that undergo meiosis
Ascospores.
On routine Kinyoun acid-fast stain, ascospores stain red and vegetative cells stain blue.
Aspergillis in a lung specimen (Ag stain)
In tissue, Aspergillis produces hyphal filaments only. Note the cross walls and regular 45o angle branching of the hyphae. Compare this to Candida albicans (produces yeast and hyphae) and Rhizopus (produces large, aseptate hyphae with irregular branching).
Aspergillus
ID Fungus
Aspergillus flavus
Aspergillus fumigatus
Chains of conidia on phialides arising from a swollen vesicle. Compare this with Penicillium and Scopulariopsis. Aspergillus is an opportunistic fungus.
ID fungus
Aspergillus fumigatus
Antigen used to detect Aspergillus
galactomannan
Aspergillus nidulans
This species is most likely to produce a cleistothecium, indicated by the yellow arrow
3.5 day old brown/black smooth yeast colony
Usually considered a contaminant but visceral infections reported
Aureobasidium pullulans
What is the identifying characteristic of Aureobasidium pullulans?
Black yeast-like colony
Bent-knee conidiophores
Beauveria
ID Fungus
Bipolaris spp.
The production of polar germ tubes is a characteristic that is associated with which dematiaceous fungi?
Bipolaris
ID fungus
Candida albicans is a yeast that produces white and creamy colonies.
May see starring of colonies, particularly on CHOC agar
Candida albicans can be differentiated from other yeasts by its positive germ tube test.
Candida albicans in sputum (Gram stain)
Note the budding forms and pseudohyphae. Yeast usually stain purple with a Gram stain, but this slide has been overdecolorized so some look pink.
Appearance of Candida albicans on chromagar
mottled green
Candida albicans in tissue (Ag stain)
Budding yeast (Blastoconidia), pseudohyphae and true hyphal forms all in the same tissue are characteristic of Candida albicans infection. The only other fungus that has yeast and hyphae in the same specimen is Malassezia furfur but it is usually only found in the superficial skin infection called tinea versicolor.
Chlamydospores of Candida albicans
When Candida albicans is grown on a “starvation medium” such as corn meal agar, it produces diagnostic large, round, thick-walled structures called chlamydospores. Budding yeast (blastoconidia) and pseudohyphae are also seen.
Appearance of Candida dublinensis on chromagar
solid green
Observed in the bottom photograph is the surface of a niger seed agar plate on which are growing inoculation streaks of two different yeast species, the one to the left representing the clinical isolate; the one to the right a control strain.
Candida dubliniensis is the correct response. Distinctive is the appearance of rough colonies with extending “feet” from the outer margins as seen in the streak to the left on the surface of the niger seed agar plate, in contrast to the colonies with smooth borders as observed in the control streak of Candida albicans as seen to the right. Clinical cases of oropharyngeal thrush may be obsereved in patients with AIDS, and niger seed (“bird seed”) agar plates should be set up to identify C. dubliniensis. Carbohydrate assimilation profiles, inoculation to CHROMagar or the use of species-specific DNA probes may also be performed to make this distinction.
Candida krusei on chromagar
lavender + DRY
Photomicrograph of yeast grown on cornmeal agar
Candida parapsilosis
Spider or cross match stick colonies is characteristic
Appearance of Candida parapsilosis on chromagar
light pink Also known to give off multiple colony types
Appearance of Candida tropicalis on chromagar
blue-purple (periwinkle)
Rapid test used to identify C. albicans
Germ tube. A positive germ tube is the initial growth of true hyphae. It grows straight out of the cell and the base is not constricted, unlike pseudohyphae which are elongated buds.
Chaetomium produces a fruiting body called an ascocarp which is covered with hair-like protrusions (setae) and contains large numbers of oval ascospores.
Taken from patient with verrucous (warty) dermatitis, can be ulcerated or crusted
Chromoblastomycosis
Often described as “copper pennies”
ID disease
Chromoblastomycosis is a chronic disease that follows inoculation of soil molds into subcutaneous tissue. Typical lesions are large warty growths frequently described as cauliflower lesions.
The four organisms that cause chromoblastomycosis are Cladophialophora (Cladosporium) carrionii, Phialophora verrucosa, and two Fonsecaea spp.
ID fungus causing Chromoblastomycosis
Colonies of Cladophialophora carrionii grow slowly and tolerate temperatures up to 37º C.
Microscopic ID
The hyphae are septate and dematiaceous (dark).
Laterally and terminally produced conodiophores bear long branching chains of brown, smooth, oval conidia that are easily disrupted.
Dark scars on the conidia are typical at the points of attachment.
ID fungus causing Chromoblastomycosis
Fonsecaea are dematiaceous molds that may produce four types of conidiation.
Fonsecaea type: compact conidiophores produce conidia borne on slightly swollen denticles and may give rise to secondary and successive rows of conidia.
Rhinocladiella type: oval conidia are borne on swollen denticles at the tip and along the sides of the conidiophore. (Pictured)
Cladosporium type: conidiophores produce shield-shaped conidia that bear oval conidia in branching short chains. The conidia have scars of attachment.
Phialophora type: vase-shaped phialides with collarettes produce oval to round conidia.
Key characteristics of chromomycosis molds
Dark, velvety surface
Growth takes more than five days
Chromomycosis
Long chains of elliptical condidia separated by a distinct scar, called a dysjunctor
What type of sporulation is this?
Cladosporium sporulation
Chromomycosis
Small clusters and short chains of elliptical conidia produced from the tip of a conidiophore.
What type of sporulation is this?
Exophiala sporulation
ID fungus causing Phaeohyphomycosis
Colonies of Exophiala spp. are slow growing with a dark olive to black yeast-like appearance.
- As the colony matures, the texture becomes velvety.
- The reverse is black.
Microscopic ID
- Exophiala spp. produce profuse oval conidia.
- The conidiogenous cells are annellides. As each conidium is produced, a scar forms at the terminal end of the annellide.
Chrysosporium is a large, diverse group which produce aleurioconidia that are usually unicellular and form at the ends of short conidiophores, intercalary, or directly from the hyphae.
two day rapid growth at 30oC
Circinella spp.
Distinct backward curve of the sporangiophores
ID fungus causing Phaeohyphomycosis
Cladophialophora bantiana grows at a moderate rate.
- Colonies are olive to gray-black with a velvety texture.
- The reverse is black.
Microscopic ID
- The conidiophores of Cladophialophora bantiana are poorly differentiated from the septate hyphae.
- The conidiophores produce long chains of oval conidia.
ID fungus that appeared after 8 days on SabHI from a darkened superficial skin infection
Cladophialophora carrionii
Causative agent of valley fever
(flu-like symptoms, pneumonia, skin nodules, arthritis)
Coccidioides immitis
Fungal conidia type
Annelloconidia are formed by budding that leaves ring-like scars on the mother cell (annellide).
The ring-like scars are useful morphological features which help to distinguish molds that produce annelloconidia from other molds
Fungal conidia type
Blastoconidia are formed by budding. Buds are produced by de novo growth from the mother cell.
This is the manner in which most yeast cells reproduce.
Some molds have a yeast phase in which they reproduce by the formation of blastoconidia.
Fungal conidia type
Chlamydoconidia are formed by structural changes in the cell walls and septa of hyphae. They can be located terminally or within the length of the hypha.
Fungal conidia type
Phialoconidia are formed by budding from a mother cell (phialide) which may be distinguished by a collarette.
Fungal conidia type
Poroconidia are produced through a pre-existing pore on the mother cell.
Cryptococcus Capsule (India Ink Wet Mount)
Stain used for capsule visualization of Cryptococcus neoformans
India ink
Fungus infecting immunocompetent patients because of highly virulent alpha-mating forms
Cryptococcus gattii
ID cause of systemic mycosis
The India ink preparation is the traditional method used to look for Cyptococcus neoformans in cerebrospinal fluid.
The yeast’s capsule creates a halo around the cell.
The India ink preparation is often replaced by an antigen test which is more sensitive for detection of C. neoformans.
Histologic examination of clinical material occasionally reveals intracellular encapsulated yeast.
Cryptococcus neoformans may be visible on direct Gram stain of cerebrospinal fluid.
The yeast cells may vary in size.
Cryptococcus neoformans tissue section
The stained capsule of Cryptococcus appears as a fuzzy area outside the cell wall. Note that the buds of Cryptococcus have a narrow base compared to those of Blastomyces.
Any yeast from a lower respiratory site must be ruled out for…
Cryptococcus (urease positive)
Zygomycete with fruiting bodies
Cunninghamella
Curvularia produce curved poroconidia which arise from bent (geniculate) conidiophores.
Cause of black piedra
Piedraia hortae
Epidermophyton (Lactophenol blue)
Epidermophyton (Lactophenol Blue)
Athletes foot sample from a young football player
Epidermophyton floccosum
Silky pale strands projecting from the colony
Club shaped macroconidia
Epidermophyte
ID fungus
Epidermophyton floccosum causes infections of the skin and nails, but not hair.
A microscopic preparation of a E. floccosum colony demonstrates club-shaped macroconidia that may appear singlely or in clusters. The walls of the macroconidia are smooth.
Microconidia are not produced.
Epidermophyton floccosum
Epidermophyton floccusum
The characteristic club-shaped macroconidia have 2-4 septa and occur in groups of 2-3. Unlike the other dermatophytes, Epidermophyton does not have microconidia.
ID fungus
Microsporum canis causes skin and hair infections.
A microscopic preparation of a Microsporum canis colony will demonstrate spindle shaped macroconidia which have thick walls, rough exteriors, and often taper to curved apical knobs.
A few club-shaped microcondidia may be present.
Microsporum canis
Microsporum canis
The characteristic spindle-shaped, thick-walled macroconidia of Microsporum canis have up to 15 septa. Microconidia may be present.
Microsporum gypsum
The characteristic ellipsoidal macroconidia of Microsporum gypsum usually have 4-6 septa. Microconidia may be present.
Cause of pityriasis(tinea) versicolor, seborrhoeic dermatitis (including dandruff)
Malassezia
ID disease and cause
Tinea nigra is characterized by darkly pigmented non-inflammed lesions in the surface of the skin.
It is caused by Phaeoannellomyces (Exophiala) werneckii, a darkly pigmented (dematiaceous) mold.
A KOH preparation of skin scrapings from a tinea nigra lesion would demonstrate the presence of dark hyphal elements.
Cause of tinea nigra
Hortaea werneckii
ID disease and agent
Tinea versicolor is characterized by altered coloration of the stratum corneum due to overgrowth of Malassezia furfur, a skin commensal.
Often don’t need a culture to ID, but when Malassezia furfur is suspected as the etiological agent it is necessary to add sterile olive oil to the surface of the culture media for growth of this lipophilic organism.
Biochemicals to distinguish from T. mentagrophytes from T. rubrum
hair perforation = positive
urea = positive
BCP-MSG = profuse growth with alkalinization.
Trichophyton mentagrophytes
Note the characteristic cigar-shaped, thin-walled macroconidia indicative of the genus Trichophyton. Microconidia are usually abundant. The coiled hyphae seen in this slide are characteristic of the species Trichophyton mentagrophytes.
ID fungus
Trichophyton mentagrophytes may infect any body surface. It most frequently causes athlete’s foot.
A microscopic preparation of a T. mentagrophytes colony will demonstrate round, clustered microconidia. Spiral hyphae and thin, smooth-walled macroconidia may also be seen.
“Birds on a Fence” microconidia along hyphae is characteristic of…
Trichophyton rubrum
ID fungus
Trichophyton rubrum infects nails and the skin of hands, feet, and torso. It rarely infects hair.
A microscopic preparation of a Trichophyton rubrum colony will demonstrate teardrop shaped solitary microconidia.
Thin, cigar or pencil-shaped macroconidia may also be present.
ID fungus
Right panel: Agars 3&4 contain thiamine
Tricophyton tonsurans commonly causes ringworm of the scalp. It may also infect skin and nails.
A microscopic preparation of a T. tonsurans colony will demonstrate microconidia of variable morphology. The microconidia may appear as teardrops, pegs, clubs or round balloon shapes.
Nutritional requirement tests using Trichophyton agars can be used to separate T. tonsurans from other Trichophyton species. The growth of T. tonsurans is enhanced by thiamine and grows better on Trichophyton identification agars containing thiamine (agars #3 & #4 rather than on #1 & #2).
Trichophyton rubrum
The macroconidia of Trichophyton are characteristically cigar-shaped and thin-walled. Microconidia are usually abundant. A culture of T. rubrum is generally a bright ruby color as the name implies. Note, however, that other types of fungi may also be red.
Cause of white piedra
Trichosporon spp.
ID disease and cause
White piedra is a superficial infection characterized by soft nodules on the shaft of hair.
It is caused by Trichosporon beigelii, a yeast-like mold.
While technically a mold, Trichosporon beigelii gives the initial appearance of a yeast.
Mature colonies are yellowish white with a suede-like texture.
Trichosporon beigelii is readily identified by yeast assimilation tests and morphology when grown on corn meal agar.
Fungal infection of the skin (PAS)
Fungi that infect the skin are called dermatophytes. These include Epidermophyton, Microsporum, and Trichophyton. The presence of a fungal infection is distinguished by seeing characteristic fungal hyphae in a skin scraping. In order to distinguish hyphae from artifacts, you should look for branching parallel walls and septa (not always clearly seen).
Genera of dermatophytes
Epidermophyton, Microsporum and Trichophyton.
Genera of thermally dimorphic fungi
Blastomyces, Coccidioides, Histoplasma, Paracoccidioides, Sporothrix
Blastomyces
Blastomyces
Broad-based budding yeast
Dimorphic fungi with lollipop conidiophore at room temp
Blastomyces dermatidis
Blastomyces dermatidis mycelial phase
The mycelial phase of Blastomyces is non-descript and indistinguishable from the mycelial phase of Paracoccidiodes brasiliensis.
ID cause of systemic mycosis
Blastomyces dermatitidis is a thermally dimorphic fungus, which grows as a mold at 25ºC and as a yeast at 37ºC. Mold colonies of Blastomyces are slow-growing and are white to beige with a fluffy texture.
Oval to round conidia form at the end of short conidiophores.
Conversion of the mold to the yeast phase (or yeast to mold) is important for identification of Blastomyces.
A DNA probe is commercially available for confirmation.
Blastomyces dermatitidis tissue section (Ag stain)
Note the broad base of the buds and the relatively large size of these yeast forms
Blastomyces dermatitidis tissue section (PAS stain)
Note the broad-based buds and the relatively large size of these yeast forms. You must use good lighting to view this slide because yeast are stained lightly. Compare the PAS stain to the Gomori silver stain.
Blastomyces dermatitidis yeast phase
Note the large size and broad based buds of the yeast cells.
Saprophytic counterpart of Blastomyces
(Shares mold form but is not thermally dimorphic)
Chrysosporium spp.
Coccidioides immitis
ID cause of systemic mycosis
Coccidioides immitis is a moderately rapid-growing dimorphic mold.
A DNA probe is available to distinguish Coccidioides from other white fluffy molds.
With age, the hyphae of Coccidioidesbegin to form arthroconidia. The arthroconidia are barrel-shaped and alternate with empty cells (disjunctor cells).
The arthrocondia of Coccidioides are readily airborne and pose a serious hazard to laboratory personnel. Therefore, it is recommended that all molds be handled in a biosafety cabinet.
Coccidioides immitis mycelial phase (Lactophenol)
Note the barrel shaped arthroconidia with alternating spaces that are characteristic of Coccidioides. When the hyphae break into single fragments of conidia, small tags remain attached to the corners, enabling the conidia to easily move in air currents. Compare with Geotrichum.
Coccidioides immitis spherule (KOH mount)
The endospore-filled spherule (Stained dark) is only formed when Coccidioides is growing in tissue. In culture it grows as a mold.
Coccidioides immitis spherule in brain (PAS)
The endospore-filled spherule (Stained dark) is only formed when Coccidioides is growing in tissue. In culture it grows as a mold.
Coccidioides immitis spherule in tissue (Ag Stain)
The endospore-filled spherule (Stained dark) is only formed when Coccidioides is growing in tissue. In culture it grows as a mold.
Saprophytic counterpart of Coccidioides immitis
Malbranchia spp.
Histoplasma capsulatum
ID cause of systemic mycosis
Histoplasmosis is caused by Histoplasma capsulatum, a thermally dimorphic fungus, that appears as small, non-encapsulated yeast cells in macrophages in host tissue and as a mold in the environment.
Histoplasmosis is distributed worldwide. The endemic areas in the United States include the Ohio-Mississippi valleys where the organism is found in soil enriched with bird or bat droppings.
A DNA probe is available to distinguish Histoplasma from other white fluffy molds.
Histoplasma capsulatum in brain (Ag stain)
The tiny yeast, stained dark, are located intracellularly.
THIS IS AT 100X!
Histoplasma capsulatum mycelial phase
Notice the tuberculate (rough edge) macroconidia and the infectious microconidia. The mycelial phase forms when Histoplasma is grown at room temperature. Note that Candida also forms similar forms but they are smooth and only form at 37oC on nutrient poor media such as corn meal agar.
Histoplasma capsulatum mycelial phase
Histoplasma in tissue (PAS stain)
The tiny yeast, stained dark red, are located intracellularly and are best observed with the 100X lens. Notice the shrinkage of the stained cytoplasm from the yeast wall results in a halo effect that can be mistaken for a capsule. The species name reflects the capsule-like appearance,
Saprophytic counterpart of Histoplasma
Sepedonium
Paracoccidiodes brasiliensis tissue section (Ag stain)
Note the multiple buds. Sometimes these appear as tiny “blebs” on the surface and other times they look like “Mickey Mouse ears”.
Paracoccidioides brasiliensis
ID cause of systemic mycosis
Paracoccidioidomycosis is caused by Paracoccidioides brasiliensis, a thermally dimorphic fungus, that appears as large, multiply budding yeasts in host tissue and as a mold in the environment.
Paracoccidioidomycosis is limited to Central and South America. It originates as a mild pulmonary infection that may disseminate hematogenously to the skin.
ID
- The mold form of Paracoccidiodes brasiliensis does not usually produce distinctive structures. Chlamydoconidia, arthroconidia, and microconidia may be present.
- At 37ºC, Paracocidioides brasiliensis produces yeast cells with multiple buds often described as sailor’s wheel or Mickey mouse ears
Paracoccidioides brasiliensis yeast phase
Note the multiple buds of Paracoccidioides. Sometimes these appear as tiny “blebs” on the surface and other times they look like “Mickey Mouse ears”.
Skin nodules in workers in Brazil
10 day old colonies- grey/white. Look like cobwebs
Tease mount of mycelium- narrow septate hyphae with oval conidia at tip
Paracoccidioides brasiliensis
ID fungus
Sporotrichosis follows a penetrating wound which inoculates the subcutaneous tissue with a soil mold, Sporothrix schenckii. In developed countries, the typical history involves a deep puncture from a rose thorn.
At 25-30ºC, slender tapering conidiophores are produced at right angles from thin hyphae. A cluster of pear-shaped conidia borne on denticles are produced at the tip of the conidiophore which may be slightly swollen.
A second type of conidium is produced along the sides of the hyphae.
The conidia turn dark with age.
At 35-37ºC, round, oval or elongated budding yeast cells are seen.
The dimorphic fungus that may produce black, yeast-like colonies after prolonged incubation at 37oC is…
Sporothrix schenkii
Yeast colonies evolve from gray-yellow, to brown, to brown-black, and finally jet black
Sporothrix schenckii yeast phase
Note the elongated buds which are characteristic of Sporothrix.
Sporothrix schenckii yeast phase
Zoom in and ID
Sporothrix schenckii yeast phase from a lab mouse
Note the elongated buds which are characteristic of Sporothrix. This slide was made from a specimen taken from a lab mouse that was injected with a culture to verify the dimorphic characteristic of the fungus. Microscopic exam of a natural infection would only rarely yield the elongated yeast.
Epicoccum species is the correct response. The rapidly growing, black-pigmented colony is characteristic of one of the pheohyphomyces, but is not specific for any given species. The identification is made by observing the distinctive formation of small multi-celled macroconidia divided by both transverse and longitudinal septa (muriform) that arise from short conidiophores as illustrated in the photomicrograph.
Epicoccum produces poorly differentiated conidiophores and dark, rough, spherical conidia with transverse and longitudinal septa (muriform).
ID fungus causing mycetoma
Colonies of Exophiala jeanselmei are slow growing with a dark olive to black yeast-like appearance.
Exophiala jeanselmei produce profuse oval conidia. The conidiogenous cells are annellides. As each conidium is produced, a scar forms at the terminal end of the annellide.
Exserohilum
The genus name Exserohilum is derived from the nipple-like protrusion that extends from the hilar cell. These conidia are long and pencil-shaped with multiple cells enclosed in sac-like distosepta
Exserohilum
Slow growing mold with deep radial grooves
Fonsecaea pedrosoi
Four classes of fungi responsible for human infections.
Ascomycetes, Deuteromycetes, Zygomycetes, and Basidiomycetes.
Fusarium
The macroconidia are multicellular, slightly curved, and arise from phialides at the ends of slender conidiophores. (bananas)
The microconidia vary from oval to cylindrical in shape, may be uni- or multicelluar, and cluster at the ends of slender phialides.
The microconidia of Fusarium may be confused with the microconidia of Acremonium.
Fungus associated with mycotic keratitis (fungal infection of the cornea).
Fusarium spp
Geotrichum mycelia (Lactophenol blue)
This common saprophyte has arthroconidia that can sometimes be confused with the arthroconidia of Coccidioides immitis. Note, however, that the arthroconidia of Geotrichum do not have alternating spaces like those of Coccidioides.
72 hour growth on Sabouraud’s + Methylene blue mount
Gliocladium
Gliocladium species are supported by multiple conidiophores as shown in this photomicrograph, much as the cupped fingers would support a tennis ball.
Ascospores are flattened, resembling a derby hat
Hansenula anomela
4 day growth
Helminthosporium spp.
Endemic region of Histoplasma capsulatum
Mississippi and Ohio River Valleys
Particularly in caves (bat guano)
Dolphins with warty lesions near columbia and Brazil likely have…
Lacazia loboi
Appear as a string of lemon-shaped yeasts in tissue,
Madura Foot – Monosporium apiospermum
Malassezia furfur (H&E Stain of Tinea versicolor)
Careful observations will yield BOTH yeast and hyphal forms, which are diagnostic for a superficial skin infection (tinea versicolor) caused by Malassezia furfur.
Malessezia furfur (KOH Mount)
Tinea capitis in children
Woods lamp shows green fluorescence
Cultures grew fungi with aerial hyphae and terminal chlamydospores
Microsporus audouinii
Mucor
Mucor
A granule from Mycetoma (Madura foot)
Madura foot is a clinical syndrome of swollen lesions with draining sinuses. It can be caused by a variety of bacteria (Actinomycetales) and approximately ten different fungi. Drainage contains granules which are actually microcolonies of the etiologic agent. This slide is from a fungus infection and shows a mass of broad septate hyphae, some of which are cross sections. Infections caused by bacteria such as Actinomycetes show filamentous growth that is much smaller in diameter.
lesions characterized by swelling, draining fibrotic channels (sinuses), and granules of the causative organism.
Mycetomas
Mycetomas are caused by a number of soil organisms including filamentous gram-positive bacteria and molds which are introduced into tissue via a puncture wound.
From primary subcutaneous lesions, mycetomas errode into contiguous tissues including muscle and bone.
Bacterial cause of mycetomas
Nocardia spp. are a common cause of bacterial mycetomas.
Nocardia spp. are weakly acid-fast and may appear beaded on stained preparations.
In long-standing infections the organism exists in granules, which should be crushed and examined microscopically.
Large dematiaceous mold colony after four days
Microscopic examination reveals large jet-black macroconidia
Nigrospora species
Dialysis fluid of 60 yo patient on antibiotics for bacterial peritonitis
Paecilomyces
Colonies grow within 72 hrs, sand colored
Oval to elliptical conidia of irregular size with pointed ends
4 days growth 30oC from dialysis fluid
Paecilomyces
Paecilomyces produces branched conidiophores with thin, elongated phialides from which chains of oval conidia arise.
Paecilomyces differs from Penicillium by its thin, tapering, widely spread phialides.
Penicillium
Penicillium produces simple or branched conidiophores with tightly clustered flask-shaped phialides bearing chains of round conidia.
Penicillium differs from Paecilomycesby its thick, flask-shaped, tightlly clustered phialides.
Sputum specimen of a person who had traveled to SE Asia
Penicillium marnefei
Microscopic looks like penicillium
Red pigment = marnefei
Only dimorphic Penicillium species
Penicillium marnefeii
In SE Asia, diagnosed by histology showing intracellular fission yeast that look like sausages. Strong correlation with AIDS diagnosis
Penicillium
Chains of conidia arise from branched conidiophore, resulting in a “paint brush” arrangement. Compare this to Aspergillus and Scopulariopsis.
subcutaneous cysts or diffuse lesions containing darkly-pigmented hyphae.
Phaeohyphomycosis
ID fungus causing Phaeohyphomycosis
Phialophora richardsiae is a slow-growing dematiaceous mold.
- The obverse appearance is dark gray-green, brown or black and velvety to wooly.
- The reverse is black.
Microscopic ID
- Hyphae are septate and hyaline to brown in color.
- Vase-shaped or cylindrical phialides are produced on the hyphae. They may be single or branched.
- A saucer-like collarette forms at the tip of the phialide.
- Round to oval conidia typically cluster at the tip of the phialide.
ID fungus
Phialophora richardsiae
Slow growing dark brown mold colonies
Fruiting heads in microscopic exam
Phialophora verrucosa
ID fungus
Phialophora verrucosa
ID fungus causing Chromoblastomycosis
Phialophora verrucosa is a slow-growing dematiaceous mold.
Microscopic ID
Hyphae are septate and hyaline to brown in color.
Vase-shaped or cylindrical phialides are produced laterally and terminally on the hyphae. They may be single or branched.
A distinct cup-like collarette forms at the tip of the phialide. Round to oval conidia typically cluster at the tip of the phialide.
This organism was isolate from a case of chromomycosis. ID?
Phialophora verrucosum
The segmented dark-staining grains seen in this photomicrograph are most commonly seen in cases of chromomycosis. Of the fungal species listed in this exercise, only Phialophora verrucosum is associated with chromomycosis and has the capability of producing the grains seen in the photograph.
Phoma produces conidia within a spherical structure called a pycnidium.
An opening in the pycnidium (ostiole) allows the mature, oval, unicellular conidia to disburse.
Phoma spp.
Pithomyces produces barrel-shaped, muriform condia on short, poorly differentiated conidiophores.
Pneumocystis carinii
Until recently, this opportunistic fungus that is a common cause of pneumonia in AIDS patients was thought to be a protozoan parasite. Stains of bronchial specimens show “cysts” that are somewhat spherical but often collapsed.
Since the organism cannot be cultured in the laboratory, Pneumocystis carinii is usually identified by staining lung tissue or secretions with the Gram-Weigert stain and/or histologic stains.
Stain used to detect Pneumocystis carinii.
P. carinii cysts, which stain blue with Gram-Weigert, are round to oval in shape.
Pneumocystis jiroveci
Until recently, this opportunistic fungus that is a common cause of pneumonia in AIDS patients was thought to be a protozoan parasite. Stains of bronchial specimens show “cysts” that are somewhat spherical but often collapsed.
Unculturable unicellular fungus lacking ergosterol that causes pneumonia
Pneumocystis jiroveci
Human-restricted disease common in AIDS, stem cell transplant, and organ transplant patients
Pathophysiology: trophic forms block gas exchange in alveoli, can lead to life-threatening hypoxia and asphyxiation (foamy eosinophilic intra-alveolar exudates)
Ingredient added to media to inhibit saprophytic molds in favor of slow-growing dimorphic fungi
Cycloheximide
Protocol for fungal cultures
Fungal cultures are held for 3 weeks Examined daily for the first three days, then twice a week moving forward Yeast are very convex. Typically look like white pearls. –> do germ tube Bacteria tend to be flatter and more translucent. Ignore these. We are only ruling out fungi Moulds get sent to M2 bench for workup.
Germ tube procedure
Pick colony with the mini-pipette and inoculate serum. Leave pipette in and place in heat block. 2-3 hours later, make wet mount and examine under 40x A positive germ tube test has parallel walls emerging from the yeast. No pinching! An elongated/ovoid cell with pos germ tube coming out towards one end is often C dublinensis
Dark colored colonies on Guizotia abyssinica (bird seed) agar are…
Cryptococcus neoformans
Produces phenoloxidase, which oxidizes the ceffeic acid in the medium to melanin, producing red-brown pigmentation
Preparation used when specimens such as hair, nails, skin or tissue are to be examined for fungal elements.
10% potassium hydroxide (KOH). KOH digests the host cellular material allowing the fungal elements to be more easily seen.
Fluorescent technique to enhance sensitivity of fungal preparations.
KOH/Calcofluor. Calcofluor binds to the chitin in fungal cell walls. The bound compound fluoresces when exposed to UV light.
Malassezia needs what added to media to grow?
OIL
Always work with molds in a…
biosafety cabinet to protect from spores
ID fungus causing a mycetoma
Sexual phase on left, Asexual phase on the right
Pseudallescheria boydii (When the sexual form of this mold is present it is called Pseudallescheria boydii, otherwise it is called Scedosporium apiospermum.)
Microscopic ID
Pseudallescheria boydii produces cleistothecia, large brown structures containing oval ascospores, which are released when the cleistothecia bursts.
The asexual form, Scedosporium apiospermum, has oval conidia on long slender conidiophores.
House mouse grey colony
Microscopic- lollipop conidiophores, branching sheath arrangement, ascospores
Pseudoallescheria boydii
Dematiaceous mold with single condidia in succession both laterally and around the tip of a straight phialide.
Rhinocladiella
Identify the style of sporulation
Rhinocladiella sporulation is the correct response. Conidia are produced singly, directly, and laterally in compact rows from the sides of the hyphae. This form of sporulation is commonly observed as one of the identifying forms produced by certain strains of Fonsecaea pedrosoi.
Rhizopus
Like the other Zygomycetes, Rhizopus has non-septate hyphae and produces sporangia filled with sporangiospores. It is characterized by the root-like structures called rhizoids at the base of the sporangiophore.
Rhizopus in a kidney specimen
Note the wide, non-septate hyphae with irregular branching.
Rhizopus in tissue
Note the wide, non-septate hyphae with irregular branching. The branches are often at right angles. Compare this with Aspergillis and Candida in tissue. You should be able to distinguish the three.
Rhizopus spp.
Mucoid pink yeast on Sabouraud’s dextrose
Cornmeal agar reveals loose clusters of yeast cells with no pseudohyphae
Rhodotorula mucilaginosa
Pink mold in bathtubs…
Acid fast stain of 6 day cornmeal agar prep from sputum
Saccharomyces cerevisiae
What phenotypic property of Saccharomyces yeast species is helpful in establishing an ID
Ascospore production
House mouse grey colony
Scedosporium
Scopulariopsis
Relatively large, rough, lemon-shaped conidia occur in chains on branched and unbranched conidiophores. Compare the size of these to that of Penicillium.
Scopulariopsis
Scopulariopsis produce cylindrical annellides that give rise to chains of spiny, round conidia with flat bases.
Ascomycetes Sexual Spores
These are the sexual spores, or ascospores, that characterize the class Ascomycetes. The two-celled ascospores are produced in sac-like structures called an ascus. Penicillium, Aspergillus, and true yeasts are all in the class Ascomycetes.
Zygomycetes Sexual Spores
The thick walled dark colored zygospore, formed from the fusion of two aseptate hyphae, characterizes the class Zygomycetes. Rhizopus, Mucor, and Absidia are members of the class Zygomycetes..
Basidiomycetes Sexual Stage
The brown basidiospore, formed on a base called a basiium, characterizes the class Basidiomycetes. Mushrooms, rusts, smuts, and the encapsulated yeast Cryptococcus neoformans are all in the class Basidiomycetes.
Stemphylium
Dematiaceous fungi with non-descript colony
Muriform macroconidia (divided longitudinally)
“Bales of cotton” on a stick
Stemphylium spp
Classes of subcutaneous mycoses
sporotrichosis and chromoblastomycosis
ID fungus
Syncephalastrum species
Torulopsis glabrata (Lactophenol blue)
Torulopsis is a very common member of the normal flora of the oral cavity, GI tract, and urogenital tract. It only occasionally causes disease in immunocompromised patients. The tiny budding yeast forms are small compared to other common yeasts.
The production of long tapered phialides is characteristic of what genus
Trichoderma
Trichoderma is the intended selection. The border to border extensions of the colony is similar to those of Gliocladiumspecies, except the surface pigmentation is a light yellow green rather than deep green. Microscopically observed are small rather than large dense clusters of spherical conidia, here located at the tips of short conidiophores that are projected laterally from the hyphae.
Hair perforation by Trichophyton mentagrophytes
recovered from inflammatory lesion on scalp
Trichophyton tonsurans
Hair perforation test used to identify…
Trychophyton species.
A positive indicates trychophyton r…
Grey-white fungal colony
long rectangular arthroconidia with “rabbits ears”
Trichosporon beigeli
Dermatophyte ID
Trychophyton metagrophytes
Small spherical conidia irregularly spaced in loose clusters
Urease pos
7 days of growth on agar supplemented with thiamine and inositol
Middle frame shows aerial hyphae
Lower frame shows pigmented chlamydospores in chains under hyphae
Trychophyton verrucosum
3 day growth at 30 oC
Ulocladium spp.
Ulocladium produces dark, rough-walled, muriform poroconidia.
The poroconidia of Ulocladium arise from geniculate (bent) conidiophores.
ID fungus causing Phaeohyphomycosis
Colonies of Wangiella dermatitidis are slow growing.
Microscopic ID
- Wangiella dermatitidis produces profuse conidia.
- The oval yeast-like conidia are formed by conidiogenous cells known as phialides.
- The phialides are poorly differentiated from the septate hyphae.
Tiny LF colonies that appear on MAC after several days may be
yeast. Wet mount to confirm.
Edge to edge = zygomycete
Hockey stick germ tube = geotrichum candidum
Within three days at 28oC, a sputum specimen placed on Sabouraud’s dextrose media with chloramphenicol and cycloheximide produced moist, grayish growthm with a white aerial mycelium, the organism is MOST likely
Coccidioides immitis
Which of the following fungal species does NOT produce pseudohyphae on cornmeal agar?
Candida albicans
Candida guilirmondii
Cryptococcus laurentii
Cryptococcus laurentii
Cryptococcus species do not produce pseudohyphae on cornmeal
All candida but glabrata do.
