Clinical Pathology(Micro)

Front 1

What's the best way to distinguish Necator americanus from Ancylostoma duodenale?
A. appearance of eggs
B. appearance of long buccal cavity
C. appearance of mouth parts
D. absence of genital groove
E. length of worm

Back 1

C. appearance of mouth parts.
Necator has cutting plates (the “Necator grater”) while Ancylostoma has teeth. Otherwise, the other features presented in the question are remarkably similar in both
organisms. Other difference not mentioned include the geographic distribution - A duodenale is not present in the U.S.
QCCP2, Hookworms

Front 2

Which aspects of Strongyloides larva help distinguish it from hookworm larva?
A. short buccal groove
B. prominent genital primordium
C. appearance of eggs
D. A & B
E. A, B, C

Back 2

D. A & B.
The short buccal groove and prominent genital primordium help distinguish Strongyloides larva. Again recall that the eggs of the hookworms, a decorticate Ascaris egg, and
the eggs of Strongyloides are, for all intents and purposes, identical.
QCCP2, Strongyloides

Front 3

What is the most worrisome outcome of Strongyloides infection, especially in immunocompromised patients?
A. autoinfection
B. Loeffler syndrome
C. chronic carrier state
D. larva currens
E. hyperinfection

Back 3

E. hyperinfection.
Hyperinfection is a potentially lethal complication where infective worms break through the intestinal barrier (autoinfection) and then disseminate intravascularly. Needless
to say, that's bad.
QCCP2, Strongyloides

Front 4

What is the most characteristic feature of Enterobius worms in histological tissue sections?
A. prominent genital groove
B. lateral alae
C. short buccal opening
D. flattened uterine branches
E. sheathed tail

Back 4

B. lateral alae.
The lateral alae should be searched for especially in cases of appendicitis, which is a common location to find the adult worm. Eggs can be identified via the cellophane tape
test.
QCCP2, Enterobius

Front 5

Which feature(s) of microfilariae are most helpful in categorizing individual species?
A. sheath/unsheathed
B. pattern of nuclei in tail
C. presence in lymphatics
D. A & B
E. A, B, C

Back 5

E. A, B, C.
All are potential means of categorizing the microfilariae - the sheathed worms are Wuchereria, Brugia, and Loa loa. The unsheathed are Mansonella and Onchocerca. Both
Onchocerca and Wuchereria lack terminal nuclei, while Loa loa & Mansonella have nuclei to the tip and Brugia has two isolated nuclei at the tip Finally, Wuchereria and
Brugia can be found in the lymphatics, while the rest are not. In addition, the worms can be categorized according to their periodicity in the blood.
QCCP2, T3.19, Filariae

Front 6

Which organism is predominantly responsible for visceral larva migrans?
A. Onchocerca volvulus
B. Toxocara canis
C. Toxocara cati
D. Ancylostoma brazilensis
E. Dirofilaria immitis

Back 6

B. T.
Most cases of visceral larva migrans (and ocular larva migrans) are due to Toxocara canis. A small percentage is due to T. cati. Onchocerca causes corneal opacities, A.
brazilensis causes cutaneous larva migrans, and Dirofilaria causes lung infection in humans and heart infections in dogs and cats.
QCCP2, Toxocara canis & cati

Front 7

Which organism has the largest egg?
A. Clonorchis
B. Diphyllobothrium
C. Fasciola hepatica
D. Paragonimus
E. Trichuris

Back 7

C. F.
Fasciola hepatica (and buskii) have the largest human parasite eggs known (~150 microns in diameter). The eggs have a non-shouldered operculum and lack an abopercular knob.
QCCP2, T3.20

Front 8

The eggs of which species of Schistosoma can be isolated from urine?
A. S. haematobium
B. S. japonicum
C. S. mekongii
D. S. mansoni
E. S. intercalatum

Back 8

A. S. .
S. intercalatum and S. haematobium are very similar, but while S. intercalatum infects the intestine, S. haematobium prefers the veins of the bladder. S. mansoni and S.
japonicum primarily infect the liver and can lead to cirrhosis. S. mekongii is very similar to S. japonicum but in a more limited distribution in Laos and Cambodia.
QCCP2, Schistosoma (bilharziasis)

Front 9

What is the primary vector for Schistosoma?
A. Aedes mosquitoes
B. freshwater snails
C. freshwater fish
D. freshwater plants
E. pork

Back 9

B. fresh water snails.
The cercariae of Schistosoma infest fresh water snails in water where they can freely swim. The cercariae penetrate the skin and migrate to the blood vessels of the bladder
(S. haematobium), liver (S. mansoni, japonicum, mekongii) or intestine (S. intercalatum).
QCCP2, Schistosoma

Front 10

Which of the following features of Taenia saginata helps to distinguish it from Taenia solium?
A. pork tapeworm
B. unarmed rostellum
C. egg with a radially striated wall
D. proglottid with less than 13 uterine branches
E. cystercercosis

Back 10

B. unarmed rostellum.
The Taenia species have several features to distinguish them from each other. T. saginata is the beef tapeworm; T. solium is the pork tapeworm. T. saginata has an
unarmed rostellum, unlike the armed rostellum of the pork tapeworm. The proglottid of the beef tapeworm has more than 13 uterine branches (as visualized by India ink
injection), where the pork tapeworm has less than 13 branches. In addition, the pork tapeworm can cause cystercercosis, which the beef tapeworm doesn't. The eggs of
both tapeworms are identical, with thick radially-striated walls.
QCCP2, Cestodes

Front 11

Infection by this organism can be a cause of B12 deficiency:
A. Taenia solium
B. Taenia saginata
C. Schistosoma mansoni
D. Diphyllobothrium latum
E. Echinococcus granulosus

Back 11

D. D. .
Diphyllobothrium latum is noted for its ability to cause vitamin B12 deficiency by competing for binding the vitamin. It occurs primarily in Scandinavia and E. Europe.
QCCP2, Diphyllobothrium

Front 12

This organism is responsible for hydatid cysts of the liver:
A. Diphyllobothrium
B. Taenia
C. Hymenolepis
D. Echinococcus
E. Dypylidium

Back 12

D. E.
The definitive host is the dog. Ingestion of infected dog stool (oh, boy!) through intermediate hosts, such as sheep or cattle, causes the disease. The primary manifestation
is multilocular hepatic cysts, and there are several species.
QCCP2, Echinococcus spp

Front 13

All of the following organisms can show respective dual or triple infection, except:
A. Ascaris and Trichuria
B. Enterobius and Dientamoeba
C. Babesia, B. burgdorfei, and Ehrlichia
D. Hymenolepis nana and Echinococcus
E. lepromatous leprosy and Strongyloides

Back 13

D. H and E.
There is no known association between Hymenolepis and Echinococcus. All the other groups have been shown to coinfect, some due to common vectors (Babesia, Lyme,
Ehrlichia), some due to host immune status (leprosy and Strongyloides hyperinfection).
QCCP2, Take-home points

Front 14

B cell (humoral) immunodeficiency increases susceptibility to this organism:
A. Giardia
B. Trichomonas
C. Toxoplasma
D. Strongyloides
E. Cryptosporidium

Back 14

A. G.
Cryptosporidium, Toxoplasma, and Strongyloides infections are affected by T-cell immunodeficiency, while Trichomonas is not significantly affected by immunodeficiency.
QCCP2, Parasitic infections in immunodeficient patients

Front 15

For what purpose is Niger seed agar used?
A. detecting melanin pigment in Cryptococcus
B. selective agar for Malassezia furfur
C. Aspergillus speciation
D. to visualize yeast forms
E. to detect pigment in Trichophyton rubrum

Back 15

A. detecting melanin pigment in C.
Bird seed (Niger) is used to selectively demonstrate Cryptococcus neoformans, where it will form brown/black colonies due to enzymatic (phenol oxidase) conversion of
caffeic acid to melanin, within a week.
QCCP2, T3.21

Front 16

All of the following are dimorphic fungi, except:
A. Histoplasma
B. Cryptococcus
C. Coccidioides
D. Blastomyces
E. Paracoccidioides

Back 16

B. C.
Cryptococcus does not have a mold form, only yeast. Therefore, unlike Histoplasma, Coccidioides, Blastomyces, Paracoccidioides, and Sporothrix, it is not one of the
dimorphic yeasts. Other medically relevant fungi of the coccoid yeast-type, like Cryptococcus, include Torulopsis and Malassezia.
QCCP2, T3.22, Classification of fungi

Front 17

All of the following entities are in the differential diagnosis of a fuzzy colony on a plate, except:
A. hyaline septate mold
B. dematiaceous mold
C. dimorphic fungus
D. coccoid yeast
E. aseptate mold

Back 17

D. coccoid yeast.
The presence of a fuzzy colony implies the presence of a mold. Based on that, one would not expect a coccoid yeast to be in the differential diagnosis. It is important to also
note that most dimorphic fungi will grossly appear as a mold by yeast conversion.
QCCP2, Identification of a fungal isolate

Front 18

Which of the following characteristics assist with the speciation of molds?
A. rate of growth
B. type of hyphae
C. pigmentation
D. A & B
E. A, B, C

Back 18

E. A, B, C.
Each of these features - and also type of sporulation - will help to categorize molds into discrete families.
QCCP2, Identification of a fungal isolate

Front 19

Which of the following media is most helpful in distinguishing the morphology of yeasts?
A. cottonseed agar
B. cornmeal agar with Tween 80
C. urea agar
D. brain-heart infusion medium
E. potato dextrose agar

Back 19

B. cornmeal agar with Tween 80.
Cottonseed agar is used specifically to convert the mold phase of Blastomyces to the yeast form. Cornmeal with Tween 80 stimulates conidiation and chlamydospore
production, aiding in speciation. Urea agar is helpful in detecting urease which is produced by Cryptococcus neoformans. Brain-heart infusion is a non-selective medium
which will support the growth of saprophytic and pathogenic fungi. Potato dextrose agar is useful in demonstrating the production of pigment by Trichophyton rubrum.
QCCP2, T3.21, Special fungal culture techniques

Front 20

Which of the following fungi are inhibited by cyclohexamide?
A. Zygomyces
B. Aspergillus
C. Cryptococcus
D. A & B
E. A, B, C

Back 20

E. A, B, C.
Most fungal pathogens, especially dimorphic fungi or dermatophytes will grow, albeit slowly, in cyclohexamide. Zygomyces, Aspergillus, and Cryptococcus won't grow.
QCCP2, Identification of a fungal isolate

Front 21

Which of the following fungi are inhibited by cyclohexamide?
A. Zygomyces
B. Aspergillus
C. Cryptococcus
D. A & B
E. A, B, C

Back 21

E. A, B, C.
Most fungal pathogens, especially dimorphic fungi or dermatophytes will grow, albeit slowly, in cyclohexamide. Zygomyces, Aspergillus, and Cryptococcus won't grow.
QCCP2, Identification of a fungal isolate

Front 22

Which of the following dimorphic fungi needs to be plated on brain-heart infusion media with blood in order to grow as a yeast?
A. Blastomyces dermatidis
B. Histoplasma capsulatum
C. Coccidioides immitis
D. Sporothrix schenkii
E. Paracoccidioides brazilensis

Back 22

B. H.
Blastomyces grows as a yeast on cottonseed agar while Coccidioides requires specialized media to grow as a yeast. The rest of the dimorphic fungi readily grow as yeast.
QCCP2, Laboratory methods

Front 23

Which of the dimorphic yeasts is often confused histologically with the mold form of another dimorphic fungus?
A. Histoplasma
B. Blastomyces
C. Coccidioides
D. Sporothrix
E. Paracoccidioides

Back 23

E. P.
The yeast form of Paracoccidioides contains the characteristic “Mariner's wheel” configuration of irregular circumferential cytoplasmic blebbing. Similarly, the mold form of
Histoplasma has circumferential cytoplasmic buds which are more frequent and regular than those of the Paracoccidioides yeast.
QCCP2, F3.14, Dimorphic fungi

Front 24

Which of the dimorphic fungi are associated with sclerosing mediastinitis?
A. Histoplasma
B. Blastomyces
C. Coccidioides
D. Sporothrix
E. Paracoccidioides

Back 24

A. H .
Most dimorphic fungi with the notable exception of Sporothrix are infective through pulmonary aspiration - Histoplasma can cause the formation of pulmonary nodules, or
sclerosing mediastinitis. It can also be disseminated through the reticuloendothelial system, where it can migrate to the spleen or bone marrow.
QCCP2, Dimorphic fungi and molds

Front 25

Which if the following organisms is in the differential diagnosis of Coccidioides spherules?
A. Rhinosporidium seeberi
B. Histoplasma capsulatum
C. Prototheca wickerhamii
D. A & B
E. A, B, C

Back 25

E. A, B, C.
All resemble the 50-200 micron spherules that contain the small 2-5 micron endospores. Rhinosporidia is larger and found in the nasal sinus, Prototheca in the olecranon
bursa. The wall of the spherule of Coccidioides is thick, but when the spherules are released. they can resemble those of Histoplasma.
QCCP2, Dimorphic fungi and molds

Front 26

Which of the following dimorphic fungi presents the highest risk to laboratory personnel during culture?
A. Histoplasma
B. Blastomyces
C. Coccidioides
D. Sporothrix
E. Paracoccidioides

Back 26

C. C.
The mold form of Coccidioides forms barrel-shaped arthroconidia of live cells alternating with empty shells. The shell portions break easily, releasing the infective
arthroconidia into the air where they can be freely inhaled unless proper precautions are taken.
QCCP2, Dimorphic fungi and molds

Front 27

Which of the following organisms grows as a mold with smooth, “lollipop”-shaped conidia?
A. Chrysosporium
B. Blastomyces
C. Sporothrix
D. A & B
E. A, B, C

Back 27

D. A & B.A number of other molds, such as Paracoccidioides and Scedosporium can produce “lollipop” conidia. Sporothrix, however, produces a very characteristic “daisy-head”
conidia that is not easily confused with Blastomyces.
QCCP2, Blastomyces

Front 28

In what patient population has an unusual inhalational form of Sporothrix been identified?
A. the very young
B. elderly
C. immunocompromised
D. chronic alcoholics
E. smokers

Back 28

D. chronic alcoholics.
Although Sporothrix is unique among the dimorphic because its primary means of infection is percutaneous, a less common means of inhalation (like the rest of the
dimorphic fungi) has been documented in chronic alcoholics.
QCCP2, Sporothrix

Front 29

The mold form of Paracoccidioides is identical to that of which other fungus?
A. Histoplasma
B. Blastomyces
C. Coccidioides
D. Sporothrix
E. Chrysosporium

Back 29

B. B.
Paracoccidioides has been called the “South American Blastomyces” because it looks and behaves very similarly to Blastomyces.
QCCP2, Paracoccidioides

Front 30

Which of the following dermatophytes is identified by its macroconidia?
A. Trichophyton tonsurans
B. Trichophyton rubrum
C. Epidermophyton floccosum
D. A & B
E. A, B, C

Back 30

C. E.
Trichophyton species (T. rubrum, T. tonsurans, T. mentagrophytes) are identified by their microconidia, while E. floccosum and the Microsporum spp are identified by their
macroconidia. E. floccosum has “beaver tail” macroconidia with transverse septae; Microsporum canis has transverse septa also, but with serrated edges (“dog teeth”) and
pointed ends. Microsporum gypseum is very similar to M. canis but without the serrations.
QCCP2, Dermatophytes