MLS Parasitology/Mycology Exam

All of the following are examples of appropriate specimens for the recovery of fungi except:

Swab

For which clinical specimens is the Potassium hydroxide direct mount technique for examination of fungal cultures?

Skin

The India ink stain is used as a presumptive test for the presence of which organism?

Cryptococcus neoformans in CSF

Cutaneous disease involving skin, hair and nails usually indicates an infection with a:

Dermatophyte

What is the first step to be performed in the identification of an unknown yeast isolate?

Germ tube test

An isolate produced a construction that was interpreted as a positive germ tube, but Candida albicans was ruled out when confirmatory tests were performed. Which of the following fungi is the most likely identification?

Candida tropicalis

Cornmeal agar with Tween eighty is used to identify which characteristic of an unknown yeast isolate?

All of these options: true hyphae, pseudo hyphae, blastoconidia, arthroconidia, and chlamydospores

Blastoconidia are the beginning of which structures?

Pseudohyphae

An isolate from CSF growing on cornmeal agar produces the following structures:

Positive Blastoconidia.

Negative Chlamydospores.

Negative Pseudohyphae.

Negative Arthroconidia.

Which tests should be performed next?

Birdseed agar and urease

Which of the following yeast enzymes is detected using birdseed, also called niger seed, agar?

Phenol oxidase

Which of the following yeasts is characteristically positive for germ tube production?

Candida albicans

Arthroconidia production is used to differentiate which two yeast isolates?

Trichsporon cutaneum and Cryptococcus neoformans

The urease test, niger seed agar test, and the germ tube test are all used for the presumptive identification of:

Cryptococcus neoformans

Which of the following yeasts produces only blastoconidia on cornmeal Tween eighty agar?

Cryptococcus species

Ascospores are formed by which yeast isolate?

Saccharomyces cerevisiae

A germ tube negative, pink yeast isolate was recovered from the respiratory secretions and urine of a patient with AIDS. Identification?

Positive Blastoconidia.

Negative Arthroconidia.

Negative Pseudohyphae.

Positive Urease.

Rhodotorula species

Chlamydospore production is demonstrated by which Candida species?

Candida albicans

Carbohydrate assimilation tests are used for the identification of yeast isolates by inoculating media:

Free of carbohydrates

Yeast recovered from the urine of a catheterized patient receiving chemotherapy for cancer gave the following results: Tests?

Positive Germ tube.

Positive Pseudohyphae.

Positive Blastoconidia.

Negative Arthroconidia.

Positive Chlamydospores.

No further testing is needed for identification

A blood agar plate inoculated with sputum from a patient with diabetes mellitus grew very few bacterial flora and a predominance of yeast. Identification?

Negative Germ tube.

Negative Arthroconidia.

Negative Chlamydospores.

Positive Pseudohyphae.

Positive Blastoconidia.

Candida tropicalis

Dimorphic molds are found in infected tissue in which form?

Yeast phase

The mycelial form of which dimorphic mold produces thick walled, rectangular, or barrel shaped alternate arthroconidia?

Coccidioides immitis

The yeast form of which dimorphic fungus appears as oval or elongated cigar shapes?

Sporothix schenckii

The mycelial form of Histoplasma capsulatum seen on agar resembles:

Sepedonium species

The yeast form of which dimorphic mold shows a large parent yeast cell surrounded by smaller budding yeast cells?

Paracoccidiodes brasiliensis

Which group of molds can be ruled out when septate hyphae are observed in a culture?

Zygomycetes

Tinea versicolor is a skin infection caused by:

Malassezia furfur

Which of the following structures is invaded by the genus Trichophyton?

All of these options: hair, skin and nails

An organism cultured from the skin produces colonies displaying a cherry red color on Sabouraud dextrose agar after three to four weeks and teardrop shaped microconidia along the sides of the hyphae. The most likely identification is:

Trichophyton rubrum

Which Microsporum species causes an epidemic form of tinea capitis in children?

Microsporum audouinii

Microscopic examination of a fungus cultured from a patient with athlete's foot showed large, smooth walled, club shaped macroconidia appearing singly or in clusters of two to three from the tips of short conidiophores. The colonies did not produce microconidia. Identification?

Epidermophyton

Which Trichophyton species causes the favus type of tinea capitis seen in the Scandinavian countries and in the Appalachian region of the United States?

Trichophyton schoenleinii

The Hair Baiting Test is used to differentiate which two species of Trichophyton that produce red colonies on Sabouraud agar plates?

Trichophyton mentagrophytes and Trichophyton rubrum

A mold that produces colonies with a dark brown, green black, or black appearance of both the surface and reverse side is classified as a:

Dematiaceous mold

A rapidly growing hyaline mold began as a white colony but soon developed a black pepper effect on the agar surface. The older colony produced a black matte, making it resemble a dematiaceous mold. What is the most likely identification?

Aspergillus niger

Which dematiaceous mold forms flask shaped phialides, each with a flask shaped collarette?

Phialophora species

Which Aspergillus species, recovered from sputum or bronchial mucus, is the most common cause of pulmonary aspergillosis?

Aspergillus fumigatus

A hyaline mold recovered from a patient with AIDS produced rose colored colonies with lavender centers on Sabouraud dextrose agar. Microscopic examination showed multiseptate macroconidia appearing as sickles or canoes.

Fusarium species

Material from a fungus ball infection produced colonies with a green surface on Sabouraud agar in five days at thirty degrees Celsius. Microscopic examination showed club shaped vesicles with sporulation only from the top half of the vesicle.

Aspergillus fumigatus

A rapidly growing nonseptate mold produced colonies with a gray surface resembling cotton candy that covered the entire plate. Microscopic examination revealed sporangiophores arising between, not opposite, the rhizoids and producing pear shaped sporangia.

Absidia species

An India ink test was performed on CSF from an HIV infected male patient. Many encapsulated yeast cells were seen in the centrifuged sample. Further testing revealed a positive urease test and growth of brown colonies on niger seed agar.

Cryptococcus neoformans

A bone marrow sample obtained from an immunocompromised patient revealed small intracellular cells using a Wright's stain preparation. Growth on Sabouraud dextrose agar plates of a mold phase at twenty five degrees Celsius and a yeast phase at thirty seven degrees Celsius designates the organism as dimorphic. The mold phase produced thick, spherical tuberculated macroconidia.

Histoplasma capsulatum

A lung biopsy obtained from an immunocompromised patient showed many cup shaped cysts, colored gray to black, in a foamy exudate, with a green background using Gomori methenamine silver. The organism cannot be cultured because it does not grow on routine culture media for molds. Te patient was diagnosed with pneumonia that resisted antibiotic treatment.

Pnemocystis jirovecci, also called carinii

Upon direct examination of a sputum specimen, several spherules were noted that contained endospores. Growth on Sabouraud dextrose agar showed aerial mycelial elements. Te septate hyphae produced barrel shaped arthroconidia.

Coccidioides immitis

A bone marrow specimen was obtained from an immunocompromised patient who tested positive for HIV. The organism grew rapidly at three days showing a mold form at twenty five degrees Celsius, displaying conidiophores with four to five terminal metulae with each having four to six phialides. The conidia at the end of the phialides were oval and in short chains. They appear as a fan or broom when viewing under ten times zoom and forty times zoom. At thirty seven degrees Celsius, the yeast form grew more slowly, showing conidia that formed hyphal elements breaking at the septa to produce oval arthroconidia.

Penicillium marneffei

What is the specimen of choice for the initial diagnosis of Pneumocystis jirovecii, also called carinii, in an immunocompromised patient, such as someone with AIDS?

Induced sputum

A transplant patient is suspected of having invasive aspergillosis on the basis of clinical and radiological findings. Which specimen is best for the initial identification of aspergillosis by soluble antigen testing?

Serum or urine

What is the most common cause of mucormycosis infection in humans?

Rhizopus species

A thermally dimorphic fungus shows a filamentous mold form with tuberculate macroconidia at room temperature, and a yeast form above thirty five degrees Celsius. Which organism best fits this description?

Histoplasma capsulatum

After a vacation to the Southwestern United States, a midwesterner complained of flulike symptoms with fever, chills, nonproductive cough, and chest pain. Microscopic exam of sputum, cleared with KOH, revealed large, thick-walled spherules containing endospores. Upon culture, the mold phase showed septate hyphae and alternating barrel-shaped arthroconidia.

Coccidioides immitis

The incorrect match between organism and the appropriate diagnostic procedure is:

Echinococcus granulosus, routine ova and parasite examination

In a patient with diarrhea, occasionally Entamoeba histolytica or Entamoeba dispar, which has four nucleated cysts and no chromatoidal bars, are identified as being present; however, these cells, which are misdiagnosed as protozoa, are really:

Polymorphonuclear leukocytes

Charcot Leyden crystals in stool may be associated with an immune response and are thought to be formed from the breakdown products of:

Eosinophils

Parasitic organisms that are most often transmitted

sexually include:

Trichomonas vaginalis

The incorrect match between the organism and

one method of acquiring the infection is:

Trypanosoma brucei rhodesiense, bite of sand fleas

Upon examination of stool material for Cystoisospora belli, one would expect to see:

Oocysts that are modified acid fast variable

Which specimen is the least likely to provide recovery of Trichomonas vaginalis?

Feces

Which of the following is the best technique to identify Dientamoeba fragilis in stool?

Trichrome stained smear

One of the following protozoan organisms has been implicated in waterborne and foodborne outbreaks within the United States. The suspect organism is:

Giardia lamblia

A Gram stain from a gum lesion showed what appeared to be amoebae. A trichrome smear showed amoebae with a single nucleus and partially digested polymorphnuclear leukocytes. The correct identification is:

Entamoeba gingivalis

An Entamoeba histolytica trophozoite has the following characteristics:

Central karyosome in the nucleus, ingested red blood cells, and clear pseudopodia

A twelve year old girl is brought to the emergency department with meningitis and a history of swimming in a warm water spring. Motile amoebae that measure ten micrometers in size are seen in the CSF and are most likely:

Naegleria fowleri trophozoites

Characteristics of the rhabditiform, which is noninfective, larvae of Strongyloides stercoralis include a:

Short buccal capsule and large genital primordium

Visceral larva migrans is associated with which of the following organisms?

Toxocara, serology

The following organisms are linked with specific, relevant information. The incorrect combination is:

Balantidium coli, common within the United States

Examination of twenty four hour unpreserved urine specimen is sometimes helpful in the recovery of:

Schistosoma haematobium eggs

Te examination of sputum may be necessary to diagnose infection with:

Paragonimus westermani

Two helminth eggs that may resemble one another are:

Diphyllobothrium latum and Paragonimus westermani

Eating poorly cooked pork can lead to an infection with:

Taenia solium and Trichinella spiralis

An operculated cestode egg that can be recovered from human feces is:

Diphyllobothrium latum

Te adult tapeworm of Echinococcus granulosus is found in the intestine of:

Dogs

In infections with Taenia solium, humans can serve as the:

Either the definitive or the intermediate host

Humans acquire infections with Diphyllobothrium latum adult worms by:

Ingestion of raw freshwater fish

Humans can serve as both the intermediate and definitive host in infections caused by:

Hymenolepis nana

Babesia has been implicated in disease from both splenectomized and nonsplenectomized patients. Morphologically, the parasites resemble:

Plasmodium falciparum rings

Organisms and infections that under normal conditions cannot be transmitted in the laboratory are:

Ascaris lumbricoides, ascariasis

Toxoplasma gondii is characterized by:

Both A and B: Possible congenital infection and ingestion of oocysts. Cosmopolitan distribution and possible difficulties with interpretation of serological results.

Oocysts of Cryptosporidium species can be detected in stool specimens using:

Modified Ziehl Neelsen acid fast stain

Which microfilariae are usually not found circulating in the peripheral blood?

Onchocerca volvulus

Massive hemolysis, blackwater fever, and central nervous system involvement are most common with:

Plasmodium falciparum

Organisms that should be considered in a nursery school outbreak of diarrhea include:

Giardia lamblia, Dientamoeba fragilis, and

Cryptosporidium species

The incorrect match between disease and symptoms is:

Enterobiasis, dysentery

The formalin ether, AKA ethyl acetate, concentration procedure for feces is used to demonstrate:

Protozoan cysts and helminth eggs

Cysts of Iodamoeba bütschlii typically have:

A heavily vacuolated cytoplasm

The miracidial hatching test helps to demonstrate the viability of eggs of:

Schistosoma species

Organisms that should be considered in a waterborne outbreak of diarrheal disease include:

Giardia lamblia and Cryptosporidium species

Fecal immunoassays have become more commonly used to diagnose infections with:

Giardia lamblia and Cryptosporidium species

Primary infections with the microsporidia may originate in:

The gastrointestinal tract

Eye infections with Acanthamoeba species have most commonly been traced to:

Use of contaminated lens care solutions

Select the most sensitive recovery method for

Acanthamoeba species from lens care solutions or

corneal biopsies.

The use of non nutrient agar cultures seeded

with Escherichia coli

The microsporidia are protozoans, now classified with the fungi, that have been implicated in human disease primarily in:

Immunocompromised patients

When staining Cystoisospora belli oocysts with modified acid-fast stains, the important difference between these methods and the acid-fast stains used for acid fast bacilli is:

The decolorizer is weaker than acid alcohol used

for acid fast bacilli decolorizing

The incorrect match between symptoms and disease is:

Myalgias, trichuriasis

The incorrect match between organism and characteristic is:

Hymenolepis nana, striated shell

The incorrect match between method and method objective is:

Knott's concentration, the recovery of

operculated helminth eggs

The incorrect match between organism and characteristic is:

Schistosoma mansoni, egg with terminal spine

There are few procedures considered STAT in parasitology. The most obvious situation would be:

Blood films for malaria

An immunosuppressed man has several episodes of pneumonia, intestinal pain, sepsis with gram negative rods, and a history of military service in Southeast Asia twenty years earlier.

Strongyloides stercoralis

In a pediatric patient, the recommended clinical specimen for recovery of Enterobius vermicularis is the:

Series of Scotch tape preparations

Which parasite causes eosinophilic meningoencephalitis, a form of larva migrans causing fever, headache, stiff neck, and increased cells in the spinal fluid?

Ancylostoma braziliense