MAJOR PATHOGENS AND DISEASE STATES
Illustrated in the photograph is a classic example of "ringworm" as may be observed in a young child, possibly contracted from the spores of an infected dog or cat. The identification of the dermatophyte causing this infection is illustrated in the lactophenol blue stained mount photomicrograph. Select the dermatophyte causing this type of infection.
Microsporum canis
The 4-day old colony recovered on Sabouraud's dextrose agar, as illustrated in the top photograph. The specimen was taken from a skin infection incurred by a 45 year old farmer. The microscopic appearance, obtained from the surface mycelium of the colony, is illustrated in the lactophenol blue mount in the bottom image. What is the fungal isolate shown?
Microsporum gypseum
The following are described as rapid growing, opportunistic fungi that are differentiated based on the presence of sporangiospores, the shape of the columella, presence or absence of rhizoids, and the location of the rhizoids on the stolon.
Mucorales species
Malassezia furfur is the cause of tinea versicolor. To cultivate this organism, the agar should be overlaid with:
Olive oil
The 10-day-old colonies grown on SABHI agar incubated at 30° C as illustrated in the top photograph are characteristic of those recovered from skin nodules of workers living in South America, especially Brazil. Although a dimorphic fungus might be suspected from the appearance of the slow-growing, gray white, cob-web like colonies, the final identification can be confirmed by observing the microscopic appearance of tease mounts prepared from the surface mycelium, as observed the bottom photograph. Based on these descriptions, what is the most likely identification?
Paracoccidioides brasiliensis
Which dematiaceous fungi affects the joints causing septic arthritis?
Phialophora spp.
All of the following are considered opportunistic pathogens EXCEPT
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
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 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
Which genera does not belong to the dermatophytes?
Rhizopus
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 - negative Urease - positive Blastospores - positive Arthrospores - negative
Rhodotorula spp.
Which of the yeasts listed below is commonly used in baking?
Saccharomyces cerevisiae
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 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
Which of the following fungi is the cause of tinea pedis, ringworm of the feet?
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
The upper image to the right depicts a small circular white colony with a downy surface, recovered from a skin scraping specimen after 7 days of growth on agar supplemented with thiamine and inositol. The identification is made by observing the aerial hyphae (middle image) and the underlying chains of pigmented chlamydospores among the hyphae (lower image). Based on this information, what is the most likely identification of this dermatophyte?
Trichophyton verrucosum
The following organism causes White Piedra which infects hairs on the face, scalp, and body areas:
Trichosporon beigelii
A soft, yellow to pale brown nodule is found growing around the hair shaft of an individual from a tropical location. On direct microscopic examination, hyaline hyphae with numerous rectangular arthroconidia were observed. The presence of the arthroconidia aid in differentiating this organism from other yeast. The most likely identification is:
Trichosporon species
Which of the following corresponds to a way to prevent infection with Sporothrix schenckii?
Wear gloves when gardening
Illustrated in the top image is a relatively rapidly growing 4-day-old colony on Sabouraud's dextrose agar incubated at 30o C. This colony was recovered as part of an environmental study. The colony has a wooly surface with distinctive black pigmentation both centrally and at the periphery, which was also visible when observed on the reverse of the Petri dish. Based on the microscopic presentation shown in the bottom image, identify this rapidly growing dematiaceous fungus.
Alternaria species
What is the phenotypic property of Saccharomyces yeast species that is helpful in establishing its species identification?
Ascospore production
The 4 day growth of colonies on Sabouraud's dextrose agar, as shown in the upper image, was recovered from the alveolar lavage of a 45 year-old construction worker who presented with X-ray evidence of a lung abscess. The light green colony in the upper image, with a cottony surface, shallow rugae, and a white surrounding apron was recovered on Sabouraud's dextrose agar from an induced sputum sample after 4 days incubation at 30° C. The Lacto-phenol cotton blue stain microscopic appearance from the surface colony is illustrated in the lower image. From these observations select the fungal species.
Aspergillus fumigatus
Which Aspergillus species has been recovered from the cornea?
Aspergillus fumigatus
Illustrated in the composite image on the left is a 72-hour growth on Sabouraud's dextrose agar of a finely granular, black pigmented colony obtained from a subcutaneous abscess at the site of an intravenous transfusion. The image to the right illustrates the microscopic appearance of a small inoculum taken from the surface of the center portion of the colony. A small spherical vesicle is surrounded by a row of phialides producing small, black-staining conidia. With these observations, select from the multiple choices the name of the fungus species as presented.
Aspergillus niger
Illustrated in the upper left image of the composite photograph is a 3 day old colony with a central, granular yellow surface (resembling cinnamon) surrounded by a broad white apron. This colony was recovered from a fungus ball infection of the lung. The microscopic presentation of a methylene-blue stained mount of a sample from the surface of the colony is observed in the upper right and lower left images. In the lower right image taken of a direct mount of the colony showing vegetative hyphae. With these observations, select from the list of multiple choice responses the correct fungal species as presented.
Aspergillus terreus
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
From the following molds, which one is considered an obligate pathogen, causing infections in persons who were previously healthy?
Blastomyces dermatitidis
A potentially pathogenic yeast that is usually found as normal flora in the oropharyngeal cavity and may produce thrush is called:
Candida albicans
This photomicrograph was prepared from tease mounts of 3 day-old smooth, white yeast colonies obtained from an aspirate of nasal fluid of a middle aged patient with sinusitis. Note the clusters of small blastoconidia along the pseudohyphae and also the larger spherical chlamydospores (arrow), as observed in the right lower corner. From the multiple choices below, select the identification of this yeast isolate.
Candida albicans
Which of the following organisms causes thrush?
Candida albicans
The top image is characteristic of the clinical presentation of oropharyngeal thrush that may be observed in patients with AIDS. Specimen samples sent to the mycology laboratory for culture often grow yeast colonies on agar plates within 2 - 3 days of incubation at 30° C. Observed in the bottom photograph is the surface of a niger seed agar plate growing two different yeast species. The one to the left represents the clinical isolate and the one to the right is a control strain. It is important to recognize the colonies of the clinical isolate as it may be potentially resistant to commonly used anti-fungal agents. Select the species of yeast involved in this infection.
Candida dubliniensis
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
This species of Candida accounts for around 20 percent of urinary yeast isolates.
Candida glabrata
This yeast has been found in respiratory secretions, the vagina, urine, gastric washing and the oropharynx but is mainly thought to cause vaginitis and urinary tract infections. Growth on Cornmeal Tween 80 agar demonstrates elongated blastoconidia that lie parallel to pseudohyphae (like logs on a stream).
Candida kefyr (pseudotropicalis)
All of the following Candida species can be commonly recovered in a clinical specimen of blood, EXCEPT?
Candida neoformans
Which organisms' natural habitat is part of the human microbiota?
Candida spp.
Illustrated in the top photograph are smooth white yeast colonies growing on Sabouraud's heart infusion agar (SABHI agar) after 48 hours incubation at 30o C. The colonies were recovered from a post-operative wound infection in a 65-year-old man following an organ transplant. The bottom photograph is representative of more mature colonies after an additional 24-hour incubation. The isolate was also inoculated to Cornmeal Tween 80 Agar. What characteristics do you expect to see when examining the growth from this media?
Chlamydoconidia present on the hyphae
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
Which of the following dematiaceous fungi can cause Chromoblastomycosis?
Cladophialophora 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
The top image shows a 5-day-old colony grown on blood agar and incubated at 30o C. It has a delicate cobweb-like, gray-white mycelium. Note the dark gray discoloration on the upper margin where hemoglobin pigment has been absorbed. This colony was recovered from the needle biopsy of a lung nodule that developed three months after a 45-year-old businessman returned from a business trip in Southern California. The definitive identification can be made microscopically from the observation of the distinctive hyphae as presented in the lactophenol blue mount shown in the bottom image. From these observations, select the presumptive identification of this isolate from the choices listed below.
Coccidioides immitis
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
All of the following fungal species produce pseudohyphae on cornmeal agar, EXCEPT:
Cryptococcus laurentii
Which of the following molds is classified as a zygomycete?
Cunninghamella species
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
The illustration demonstrates a dematiaceous mold that is known to cause phaeohyphomycoses and sinusitis. It produces septate hyphae, geniculate conidiophores and multi-celled, curved conidia with a swollen central cell. The most likely identification is:
Curvularia species
The most common eye complication in patients with candidiasis is:
Endophthalmitis
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 the top left image of the composite photograph is a well-circumscribed, actively progressing pink scaling lesion on the groin, termed tinea cruris or more commonly "jock itch". Illustrated in the lower left frame is a 3-day old colony growing on SABHI agar with a gray-yellow smooth surface with radiating spicules at the periphery. The microscopic features are presented in the right upper and lower photomicrographs of the slide mounts. Select the identification of this dermatophyte.
Epidermophyton floccosum
Illustrated in the top photograph is a 4-day growth of silky, light gray-white to yellow colonies grown on Sabouraud's dextrose agar incubated at 30° C, recovered from an "athlete's foot" infection (tinea pedis) of a young football player. Note the projection of delicate hyphae to the periphery of the colonies. The identification can be made by observing the conidia formations in the lactophenol blue stained mount prepared from the surface of one of the colonies. With these observations, select the species identification from the multiple choices.
Epidermophyton floccosum
In tissues infected with Histoplasma capsulatum, which of the following is usually true?
Fungus is usually intracellular
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
From the fungi listed below, which is considered to be a true pathogen that also infects immunocompromised patients?
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
The presumptive diagnosis of fungal infections may be assisted based on the geographic location or sites in which they have become endemic. One such condition, is colloquially referred to as "Spelunker's Scourge". This condition occurs after a tour or work in underground caves located in the Midwest, where dust contaminated with bird and bat dung is inhaled. Select the name of the fungus from the choices shown below that causes this endemically-acquired respiratory infection.
Histoplasma capsulatum
The transmission of which of the following organisms is associated with the guano of bats?
Histoplasma capsulatum
A patient is seen at his physician's office for scaling, flat lesions on his back that are irregular with white blotches of discoloration (top image). The bottom image shown is of a tease mount taken from the skin and stained with Periodic Acid Schiff, which reveals narrow fungal hyphae (arrows) along with 3 - 5 µm in diameter, irregular sized spherical budding yeast cells, a presentation often referred to as "spaghetti and meatballs". Which fungi is the most likely cause of infection?
Malassezia furfur
A track star was in the locker room after a competition when one of his teammates noticed light brown circular lesions on his upper back. The agent MOST likely responsible for this condition is:
Malassezia furfur
photomicrographs prepared from histological sections of a duodenal biopsy obtained from a patient with AIDS who was experiencing chronic diarrhea. Tiny intra-cytoplasmic spores are observed in both the left hand PAS stained and on the right Methylene blue-stained sections. The spores are best visualized in the PAS-stained section on the left (arrow). Stool specimens had been negative for parasites or bacterial pathogens. The acid-fast is negative with a positive Weber stain (Chromotrope 2R. Fast Green, phosphotungistic acid) confirming an identification. From the list of multiple choices, select the most probable presumptive identification.
Microsporidium specie
Which of the following organisms has been known to cause epidemic tinea capitis in children but almost never affects adults?
Microsporum audouinii