mycology
The colony in the upper image developed after 4 days of growth on Sabouraud's dextrose agar. Note the extension of the outer margin to the rim of the Petri dish. The lower image is a methylene-blue stained inoculum obtained from the surface of the colony. From the choices of fungi, select the genus described.
Trichoderma
The arrows in the image on the right point to single, long, tapered phialides that extend laterally from either side of the hyphae. This microscopic presentation is an identifying feature of which fungi?
Trichoderma species
The image in the upper right indicates the mold form of which dimorphic fungus?
Coccidioides immitis
From the list of incubation temperatures, select the one that is currently recommended as a routine temperature of incubation for the laboratory recovery of fungi from culture specimens, being both successful and cost-effective.
30°C.
The dark brown, wooly to velvety surface of the colony shown in the image to the right suggests a dematiaceous fungi. What additional feature would suggest recovery of one of the agents of chromomycosis, rather than one of the phaeohyphomycetes?
A delay in growth beyond five days
Dematiaceous molds can be broadly separated into two major groups; the agents of chromomycosis and clinically insignificant commensals or contaminants. Which of the statements below is true?
Agents of chromomycosis grow more slowly than clinically insignificant commensals or contaminants.
The microscopic illustration demonstrates the golden-brown pigmented conidia and macroconidia of the following mold
Alternaria
What is the phenotypic property of Saccharomyces yeast species that is helpful in establishing its species identification?
Ascospore production
The fungal colonies illustrated on the left image grew to maturity in 4 days. The isolate was recovered from the expectorated sputum of an elderly immune-compromised patient. The image on the right is the microscopic appearance of a lactophenol cotton blue stained mount prepared from a small sample from the surface of the colony. Note that microscopically the entire surface of a smooth spherical vesicle is surrounded by a row of phialides giving rise to small conidia.
Aspergillus flavus
The fungus illustrated in this photomicrograph was recovered from an induced sputum specimen from a 74-year-old man with chronic obstructive pulmonary disease. This isolate is most likely
A contaminant
Which of the following fungi is the cause of tinea pedis, ringworm of the feet?
Trichophyton rubrum
Which fungi has a growth rate of 2-21 days and the morphological features seen in the tissue form are round spherules 30-60 µm in diameter containing 2-5 µm endospores?
Coccidioides spp.
Which of the following fungal infections is endemic in the Southwestern United States desert regions?
Coccidioidomycosis
Illustrated in the upper left image in the composite photograph is a brown pigmented scaling lesion of the skin involving the distal forearm and anterior wrist interspersed with focal dark circumscribed nodules. The image to the upper right are small white yeast colonies with smooth surfaces. The lower images illustrate the microscopic appearance of fluid aspirated from one of the cystic lesions illustrating distinctive yeast cells. Based on these results, select the name of the infection as illustrated.
Cryptococcosis
Which Aspergillus species has been recovered from the cornea?
Aspergillus fumigatus
The image on the right of a mold colony on an agar plate is most representative of which of the following molds?
Aspergillus niger
What is the most likely identification of a rapidly growing hyaline mold that began as a white colony and later develops a black "pepper" effect on the agar surface? As the colony aged it produced jet black, powdery colonies which then caused it to resemble a dematiaceous mold
Aspergillus niger
Which Aspergillus species show biseriate with phialides covering the entire surface of a spherical vesicle with black conidia as microscopic morphological features?
Aspergillus niger
All of the following fungi are appropriately listed with their respective morphology, EXCEPT
Aspergillus sp. produce ascospores
A farmer is diagnosed with a fungal respiratory infection. A fungal culture demonstrates rapid growth of a blue-green colony on fungal media. Microscopically, the organism demonstrated septate hyphae with long conidiophore ending in a dome-shaped vesicle. Long chains of conidia protrude from the vesicle as demonstrated in the illustration. The most likely identification is
Aspergillus species
Although care should be taken when working with all fungus cultures in the laboratory, personnel are particularly prone to develop laboratory acquired infections from the inhalation of airborne species of
Coccidioides immitis
In this photomicrograph, several dematiaceous hyphae with long, flask-shaped, tapered phialides that have flat saucer-like terminus are seen (arrow). This feature is most characteristic of which of the following fungal species?
Pleurostomophora richardsiae
The dimorphic molds exist in both mold and yeast forms depending on the temperature of incubation. In the laboratory, when cultures are incubated at 30o C, all of the dimorphic fungi will produce mold colonies, usually within 10 - 14 days. When cultures are incubated at 35o - 37o C, yeast colonies develop usually within 3 - 5 days, with the exception of one of the dimorphic species. From the options shown below, select the genus that does not produce yeast colonies when cultures are incubated at the higher temperature
Coccidioides immitis
Immunocompromised patients, such as those with Acquired Immunodeficiency Syndrome (AIDS) are at an increased risk of contracting an unusual form of pneumonia from which of the following microorganisms?
Pneumocystis jiroveci (carinii)
The top image shows a 5-day old entire colony with distinct outer borders that was incubated at 30° C. The surface is a delicate silky, light gray-white mycelium. The reverse of the colony appears white. This appearance is non-specific. The bottom image is a photomicrograph of a lacto-phenol blue stained mount of a small inoculum taken from the surface of the colony. What is the most likely identification?
Beauveria
Illustrated in the photograph to the right is a lactophenol cotton blue preparation from a culture of a dematiaceous fungi. This fungi is known to cause phaeohyphomycosis and can be found in sites such as subcutaneous tissue, brain, eyes, and bones. Which of the following fungi is represented?
Bipolaris species
The production of polar germ tubes is a characteristic that is associated with which of these dematiaceous fungi?
Bipolaris species
From the following molds, which one is considered an obligate pathogen, causing infections in persons who were previously healthy?
Blastomyces dermatitidis
From the list of fungal species below, select the one for which optimum recovery in a laboratory culture requires the use of an enriched agar base such as inhibitory mold agar, SABHI (Sabouraud's dextrose agar + heart infusion agar), or brain-heart infusion with cycloheximide and chloramphenicol
Blastomyces dermatitidis
This image illustrates a lactophenol blue mount prepared from a mold recovered after 7 days incubation on brain heart infusion broth. The individual microconidia, each borne by a delicate conidiophore, suggests the mold form of the following organism
Blastomyces dermatitidis
Yeast colonies, as illustrated in the top image, can be cultured in the mycology laboratory either by transferring samples from growing colonies to enriched agar incubated at 35o - 37o C, or by setting up a second culture for incubation at the elevated temperature. The yeast colonies appear smooth and pasty, off-white pigmentation. The species identification is made by observing the morphology of a yeast cell as observed in lactophenol blue-stained mounts as shown in the bottom image. With these observations, select the correct presumptive identification of this isolate from the choices listed below.
Blastomyces dermatitidis
Illustrated in the top photograph are small, smooth, 48-hour old white yeast colonies growing on potato dextrose agar. The rudimentary spikes from the surface of the colonies (arrows) indicate that a germ tube test should be performed. The bottom image is the germ tube test for this isolate. What is the identification of this yeast isolate?
Candida albicans
The formation of germ tubes after 2 hours of incubation in plasma at 35° C leads to the presumptive identification of which of the following yeasts?
Candida albicans
The smooth, pasty appearing 72 hour yeast colonies growing on blood agar shown in the upper image are non-specific and further studies must be performed to make the identification. One of these studies is a cornmeal agar preparation is illustrated in the bottom photomicrograph in which tiny, uniform, spherical cells are arranged in tight clusters. This yeast is commonly recovered from urinary tract infections. Select the most likely yeast isolate
Candida glabrata
The growth of yellow-white yeast colonies with a smooth or hair-like surface within 2 - 3 days on non-selective culture media generally requires further procedures to make a presumptive identification. Microscopic observation of the subculture of colonies growing on cornmeal agar is one such approach, as illustrated in the photomicrograph. Note the "logs in stream" arrangement of elongated blastoconidia. From the multiple choices, select the name of the presumptive yeast identification.
Candida kefyr
All of the following Candida species can be commonly recovered in a clinical specimen of blood, EXCEPT?
Candida neoformans
The growth of yellow-white yeast colonies with a smooth or hair-like surface within 2 - 3 days on non-selective culture media generally requires further procedures to make a presumptive identification. Microscopic observation of the subculture of colonies growing on cornmeal agar is one such approach, as illustrated in the photomicrograph. Note the spider-like colonies that appear along the streak line. From the multiple choices, select the name of the presumptive yeast identification.
Candida parapsilosis
the morphology of yeasts inoculated to cornmeal agar can be helpful in making a species identification. The field of view shown in this photomicrograph is most consistent with the identification of
Candida parapsilosis
The ingredient added to culture media to enhance the recovery of the dimorphic fungi by preventing the overgrowth of more rapidly growing, saprophytic molds is:
Chloramphenicol
The images to the right show a 4-day-old colony grown on Sabouraud's Dextrose agar (left image). It was recovered from what was considered a "contaminant" from a bacterial culture. The image on the right is a high power photomicrograph of a methylene-blue stained mount prepared from the surfaces of the colony. With these observations, select the fungus genus from the choices below
Chrysosporium
Illustrated in the top image is a slow-growing, 8-day-old colony growing on Sabouraud Dextrose with Brain Heart Infusion (SabHI) agar obtained from a darkened superficial skin infection. Although the colony is not specific for one of the fungal species causing chromomycosis, the black outer border that extends into the reverse of the colony is consistent. The identification is made by observing the distinctive conidiation illustrated in the bottom image. Which of the following organisms is represented by the description and images shown?
Cladophialophora carronii
All of the following fungal species produce pseudohyphae on cornmeal agar, EXCEPT:
Cryptococcus laurentii
The top image shows the microscopic appearance of yeast cells within a colony growing on cornmeal tween 80 agar. These same cells may also be observed in a tissue section (bottom image) taken from an area of inflammation. The tissue section is stained with Gomori Methanimine Silver and shows a clear area around the cells. Which of the following organisms could be the cause of this inflammation?
Cryptococcus neoformans
Illustrated in the top image is a circumscribed three day old colony growing on Sabouraud's dextrose agar recovered from nasal washings of a patient with sinusitis. The colony with a dark green-gray, wooly surface mycelium is not exclusive. Gray-black pigment would be observed on the reverse side. Species identification must be made microscopically. Illustrated in the bottom image is the appearance of a tease mount made from the surface of the colony. From these observations, what is the identification of this fungal isolate?
Curvularia species
Which antimicrobial is used to suppress or kill saprophytic molds in media?
Cycloheximide
A dermatophyte that produces thin-walled, two or three-celled macroconidia in clusters, and no microconidia, most likely belongs to the genus
Epidermophyton
A fungus culture from a toe-nail scraping demonstrates large, club-shaped macroconidia with no microconidia. The most likely identification is
Epidermophyton floccosum
Illustrated in this image is the fruiting head of one of the fungal agents of chromomycosis. Note the small clusters and short chains of elliptical conidia produced from the tip of a conidiophore. Which of the following choices best represents the type of sporulation illustrated in this image?
Exophiala sporulation
Illustrated in the top photograph is a circumscribed colony after 3 days of incubation at 30o C. The consistency is cottony to wooly and pigment ranges from gray to deep brown. A light pigmented outer apron is seen at the margins of growth. The reverse is dark brown to black, resulting from a darkly pigmented mycelium. As the colony morphology is not species specific, the identification can be made by the appearance of the macroconidia observed in a stained tease mount made from the surface of the colony as observed in the bottom photomicrograph. From these observations, select from the multiple choices the name of this fungus.
Exserohilum species
Illustrated in the top image is a slow-growing, 8-day-old colony with velvety brown, deep radial grooves and a black periphery consistent with one of the agents of chromomycosis. In the bottom image, note the conidiophores produced from the sides of the hyphae producing short, branching phialides, giving rise to clusters of elliptical conidia. From the list of choices shown below, select the correct presumptive identification of this isolate
Fonsecaea pedrosoi
When a fungus is suspected in causing a cutaneous infection, there are several methods that can be used to identify the fungus. To help identify a fungal isolate from tissue specimens, which of the following methods will be most beneficial?
Fungal Culture
Illustrated in the upper image is a 4 day growth of a fungus colony on Sabouraud's dextrose agar. Note the cottony to woolly surface, and the distinctive lavender, pink pigmentation. The lower image is of a lactophenol cotton blue pigmented view of long, narrow multi-celled macro-conidia that are sickle-shaped. Based on these observations, select the genus identification of this isolate
Fusarium
Which one of the following fungi is MOST likely to be seen in skin infection of burn patients?
Fusarium sp.
Which of the following species or organisms is the most likely to cause mycotic keratitis (fungal infection of the cornea)?
Fusarium species
A key laboratory characteristic by which Mycobacterium bovis can be separated from Mycobacterium tuberculosis is:
Growth inhibition by thiopine-2-carboxylic acid hydrazide (T2H)
An uncommon isolate in clinical laboratories, the gray-white colony with a hairy mycelium as illustrated in the top image is non-specific. The identification is made by microscopically observing acid-fast ascospores as seen in the bottom image. Select the fungal species characteristic of this isolate.
Hansenula anomala
From the fungi listed below, which is considered to be a true pathogen that also infects immunocompromised patients?
Histoplasma capsulatum
Illustrated in the top image is the surface of a blood agar culture plate incubated at 35°C for 3 days. Note the growth of tiny smooth, pasty, yellow-white yeast colonies. Although a presumptive identification might be made from the macroscopic morphology, confirmation is made by observing the yeasts forms in the lactophenol stained mount observed in a tease mount prepared from one of the colonies. From these observations, what is the most likely identification?
Histoplasma capsulatum
In the late 1990's, an outbreak of pneumonia was experienced by several high school students involved in a clean-up day held in a Midwestern community. One student experienced a severe disseminated infection. The colony growing on Sabouraud Dextrose with Brain Heart Infusion (SABHI) agar and incubated at 30o C and shown on the top photograph was recovered from an induced sputum specimen. The colony matured in 8 days, presenting a hair-like, cottony surface mycelium. The identification was confirmed by observation of the lactophenol tease mount obtained from the surface of the mycelium. From the list of choices below, select the name of this isolate.
Histoplasma capsulatum
Under a Woods' lamp, infected hair strands from several children with tinea capitis showed green fluorescence, and subsequent cultures grew fungi with aerial mycelia and terminal chlamydospores. These isolates are most likely:
Microsporum audouinii
Which of the following organisms has been known to cause epidemic tinea capitis in children but almost never affects adults?
Microsporum audouinii
Illustrated in the top photograph is the appearance of a 4-day old fugal colony cultured from a "ringworm" cutaneous infection. Although the appearance of the colony may suggest a presumptive identification, microscopic mounts prepared from the surface hyphae must be examined, as observed in the lacto-phenol blue stained tease mount in the bottom photomicrograph. With these observations, select from the multiple choices the identification of this dermatophyte
Microsporum canis
The Mycobacterium species capable of growing on modified MacConkey agar (crystal violet removed from the formula), as illustrated in this photograph, is:
Mycobacterium fortuitum
All of the following represent an area in clinical microbiology using molecular detection methods a routine diagnostic tool, EXCEPT?
Mycology testing
All of the following observations are consistent with the laboratory identification of Cryptococcus neoformans, EXCEPT
Negative urease test
Malassezia furfur is the cause of tinea versicolor. To cultivate this organism, the agar should be overlaid with
Olive oil
The fungal colony illustrated in the upper image was observed after 4 days incubation at 30oC and recovered from dialysis fluid of a 60-year-old patient who had been receiving multiple antibiotics for treatment of bacterial peritonitis. The lower image is of a microscopic view of a lactophenol blue stained mount taken from a small sampled of the surface of the colony. Note the distinctly pointed phialides from which long chains of small, spherical conidia are derived. What is the appropriate identification based on the colony morphology and microscopic features as observed in the lactophenol stained preparation?
Paecilomyces
The colonies observed on the agar surface in the top photograph represent 4 day-old yeast colonies converted from a mold colony suspicious for a dimorphic fungus. The identification is made by microscopically observing the characteristic morphology of the yeast cells as illustrated in the bottom photomicrograph. What is this species?
Paracoccidioides brasiliensis
The yeast forms of which of the following species of dimorphic fungi (represented in the image on the right) can be described as large yeast cells with multiple buds that are attached by narrow necks, giving the appearance of a "mariner's wheel?"
Paracoccidioides brasiliensis
The fungal colony illustrated in the upper image, observed after 4 days incubation at 30°C, was recovered from dialysis fluid of a 60 year-old patient who had been receiving multiple antibiotics for treatment of bacterial peritonitis. The colony surface is cottony and green in pigmentation. The lower image is of a methylene-blue stained section of fruiting heads observed in a mount prepared from a small sample of the colony surface. Based on the colony morphology and microscopic features, what is the genus identification of this isolate.
Penicillium
Illustrated in this image is the fruiting head of one of the fungal agents of chromomycosis. Note the long urn-shaped phialides tapered at the ends and topped with a distinctive flat, saucer shaped cap. Which of the following choices represents the type of sporulation illustrated in this image?
Phialophora sporulation
All of the following are considered opportunistic pathogens EXCEPT
Phialophora verrucosa
In observing the slow-growing, 7-day-old dark brown colonies growing on Sabouraud Dextrose with Brain Heart Infusion (SABHI) agar, note that the black pigment extends to the reverse of the colony. This provides a presumptive indication of one of the fungi involved in chromoblastomycosis. The species identification of this fungus can be made by observing the distinctive fruiting heads illustrated in the bottom image. Select the identification of the fungal species.
Phialophora verrucosa
The segmented, dark-staining grains seen in this photomicrograph are most commonly seen in cases of chromoblastomycosis. Which of the fungal species listed below is known to cause this disease?
Phialophora verrucosa
This organism is a slow-grower on Sabouraud Dextrose Brain Heart Infusion (SABHI) agar. It was recovered from a chronic recurrent cyst of the skin of the lower leg. The brown hair-like surface pigmentation appears brown-black when observed on the reverse of the colony. The identification is made by the microscopic appearance of fruiting heads. The image shows hyphae that are dark with flask-shaped phialides which form on the tips of the condiophores. What is the name of this fungus?
Phialophora verrucosa
The dematiaceous colony illustrated here grew to a diameter of 3 - 4 cm in 5 days. Which of the following fungi can be ruled out based on the information given?
Phialophora verrucosum
What is the unique colony morphology feature of Rhodotorula growing on Sabouraud Dextrose Agar (SDA)?
Pink-red/orange pigment
When working up a culture, Scedosporiumspecies may presumptively be identified if colonies have a "house mouse" gray appearance and microscopically observed are long delicate condiophores from the tips of which are produced a single oval conidium ("lollipop"). In some cases, further examination of the microscopic mount may reveal the branching, sheath-like arrangement (graphium form) of conidiophores as seen in the top image, and/or the spherical conidia-containing ascospores seen in the lower image. From the multiple choices, indicate the fungal species to be recognized.
Pseudoallescheria boydii
This gram stain smear was prepared from a sputum specimen and is viewed under oil immersion (1000X). What is the structure indicated by the arrow?
Pseudohyphae/yeast
The fungal organism in the illustration is identified as Sporothrix schenckii and is described as having a delicate 'flowerette' appearance with single-celled conidia borne in a cluster. Each conidium is connected to the tip of single conidiophore by a delicate, thread-like denticle. The mechanism of transmission for this organism is
Puncture or abrasion
The photomicrograph on the right illustrates single conidia in succession both laterally and around the tip of a straight phialide. This type of sporulation, characteristic of certain species of dematiaceous mold, is called
Rhinocladiella
Observed in the image is the microscopic appearance of a sporulation representative of one of the dematiaceous fungi causing chromomycosis. Note that spherical conidia are being produced laterally from the sides of a conidiophore. Which of the following choices represents the type of sporulation illustrated in this image?
Rhinocladiella sporulation
The colony shown in the upper image was recovered from the nasal exudate of a 28-year-old construction worker with sinusitis. The colony grew in 3 days on SabHI agar (combination of Sabouraud dextrose and BHI agar) incubated at 30o C. Note the border-to-border extension of the surface mycelium. As the colony is not species-specific, the identification of this isolate can be made by observing the lower, lactophenol blue-stained image. From these observations, select the identification of this isolate
Rhizopus species
What is the MOST likely identification of a pink yeast isolate, recovered from respiratory secretions of a patient with AIDS, that gave the following results? Germ tube - negativeUrease - positiveBlastospores - positiveArthrospores - negative
Rhodotorula spp.
Which of the yeasts listed below is commonly used in baking?
Saccharomyces cerevisiae
A yeast identification system gave a biotype number for an unknown isolate that did not differentiate between Candida tropicalis and Candida parapsilosis. This isolate could be identified as C. parapsilosis on a cornmeal agar preparation if it produced:
Sagebrush appearance with large hyphae; blastoconidia not characteristically present
The illustrated organism is the anamorph stage of Pseudoallescheria boydii that may cause pulmonary fungus ball infection, mycetomas, endocarditis, and other disseminated infections
Scedosporium species
Observed in the upper image is a yellow-brown colony growing on Sabouraud's Dextrose agar after 72 hours incubation at 30° C, as recovered from a subcutaneous abscess following a traumatic injury in an immune-compromised host. The microscopic appearance is shown in the lower image, revealing relatively large conidia arranged in long chains. Based on these features, select the fungus genus name from the multiple choices.
Scopulariopsis
All of the following fungi are considered to cause major opportunistic infections in humans, EXCEPT?
Scopulariopsis species
The dermatophytic fungus shown in this photomicrograph, is recovered from a ringworm lesion of the skin of the back of the hand of an 8-year-old boy. What was the most likely source for this fungus?
Soil in the back yard
In cases where separate fungal cultures are incubated at both 30° C and 35°-37° C, a dimorphic yeast form may develop within 3-4 days as illustrated in the top photograph. The isolate is commonly recovered from puncture wounds of the fingers, wrists or arms among rose gardeners. The yeast colony has a smooth outer white border surrounding an inner pigmented center of growth that appear to be hyphal strands. What is the yeast identified by observing the microscopic features as illustrated in the bottom lactophenol stained mount?
Sporothrix schenckii
The colonies shown in the upper image, obtained from a biopsy of an ulcerating skin lesion of the arm, are growing on agar slants of Sabouraud's dextrose agar. The lower image is a photomicrograph of a lactophenol blue mount made from a portion of the colony growing in the left slant. The diagnosis is:
Sporotrichosis
Illustrated in the upper image is a 6-day-old colony growing on the surface of Sabouraud Dextrose agar. Note the distinct light green and pink granular colony surrounded with a reddish margin with diffusion of the wine-red pigment into the agar. This type of colony may be recovered from a sputum specimen of a person with travel history to Southeast Asia. The lower image is of a microscopic mount stained with lactophenol blue. From these characteristics, select the identification of this fungal isolate
Talaromyces (Penicillium) marneffei
What is the most helpful feature in differentiating the Zygomycetes from the other hyaline molds in the clinical mycology laboratory?
The production of spores within sporangia
The colony illustrated in the top image developed after 4 days of growth on Sabouraud's dextrose agar. Note the extension of the outer margin to the rim of the Petri dish. The bottom image 2 is a methylene-blue stained image of an inoculum obtained from the surface of the colony. From these characteristics, select the fungus genus from the multiple choices
Trichoderma
The scaling, pink-white appearance of the foot shown in the photograph is characteristic of "Athlete's Foot", a skin infection incurred by athletes after barefoot walks to and from the shower stall. A cottony gray-white fungal colony grew in 5 days from a skin scraping. The identification was made by the microscopic appearance of a mount made from the colony as illustrated in the photomicrograph. From these observations, select the name of the fungal species
Trichophyton rubrum
Illustrated in the top photograph is the picture of a yellow to buff colored colony, suede-like in consistency, recovered from a hairless inflammatory lesion of the skin of the scalp of a young male athlete. The more definitive identification can be made from observation of the lactophenol blue mount illustrated in the bottom photomicrograph, prepared from a small sample of the colony surface mycelium. Based on these observations, select from the multiple choices the presumptive identification
Trichophyton tonsurans
which of the following morphological features would correspond to Phialophora verrucosum?
Urn or vase shaped phialides
india Ink is used to:
Visualize capsule
Which of the following corresponds to a way to prevent infection with Sporothrix schenckii?
Wear gloves when gardening