1.

A 22-year-old man presents with a painless 1-cm ulcer on the shaft of his
penis. Inguinal lymphadenopathy is present. The patient admits trading
drugs for sex and has several sexual partners. An RPR test result is
positive, and syphilis is suspected; however, a Gram stain of a swab
specimen from the ulcer shows no bacteria. Treponema pallidum, the
causative agent of syphilis, cannot be visualized by light microscopy
because
(A) It is transparent.
(B) It cannot be stained by ordinary stains.
(C) It has a diameter of less than 0.2 mm.
(D) The wavelength of white light is too long.
(E) Rapid movement of the organism prevents visualization.
2. Chloramphenicol, an antibiotic that inhibits bacterial protein synthesis,
will also affect which of the following eukaryotic organelles?
(A) Mitochondria
(B) Golgi apparatus
(C) Microtubules
(D) Endoplasmic reticulum
(E) Nuclear membrane
3. Which of the following structures is not part of the bacterial cell
envelope?
(A) Peptidoglycan
(B) Lipopolysaccharide
(C) Capsule
(D) Gas vacuole
(E) S-layer
4. Which of the following transport mechanisms functions without the
requirement for energy?
(A) Binding protein dependent
(B) Group translocation
(C) Symport
(D) Uniport
(E) Facilitated diffusion
5. Which of the following components is present in gram-negative bacteria
but not in gram-positive bacteria?
(A) Peptidoglycan
(B) Lipid A
(C) Capsule
(D) Flagella
(E) Pili
6. Which of the following components is present in gram-positive bacteria
but not in gram-negative bacteria?
(A) Peptidoglycan
 (B) Capsule
(C) Flagella
(D) Teichoic acid
(E) Diaminopimelic acid
7. In the fall of 2001, a series of letters containing spores of Bacillus
anthracis were mailed to members of the media and to U.S. Senate
offices. The result was 22 cases of anthrax, with five deaths. The heat
resistance of bacterial spores, such as those of Bacillus anthracis, is
partly attributable to their dehydrated state and partly to the presence of
large amounts of
(A) Diaminopimelic acid
(B) d-Glutamic acid
(C) Calcium dipicolinate
(D) Sulfhydryl-containing proteins
(E) Lipid A
8. Which of the following terms does NOT describe the bacterial
chromosome?
(A) Haploid
(B) Diploid
(C) Circular
(D) Nucleoid
(E) Feulgen positive
9. Lysozyme cleaves the β1→4 linkage between
(A) d-Alanine and the pentaglycine bridge
(B) N-Acetylmuramic acid and d-alanine
(C) Lipid A and KDO
(D) N-Acetylmuramic acid and N-acetylglucosamine
(E) d-Alanine and d-alanine
10.Mycoplasma species lack which of the following components?
(A) Ribosomes
(B) Plasma membrane
(C) Both DNA and RNA
(D) Lipids
(E) Peptidoglycan

1. C 4. E 7. C 10. E
2. A 5. B 8. B
3. D 6. D 9. D
1. MHC class I molecules need to bind peptide antigens to fold properly and
to be expressed at the cell surface. What would you expect to be the most
common health problem in a child with a defect in the function of the
peptide transporter (TAP) found in the endoplasmic reticulum?
(A) Chronic upper respiratory viral infections
(B) Parasitic infections
(C) Infections with encapsulated bacteria
(D) Pronounced allergies to household pets
(E) Autoimmune disease
2. Which major antibody molecule has the ability to cross the placenta?
(A) IgG
(B) IgA
(C) IgM
(D) IgE
(E) IgD
3. A man in his twenties presents in the emergency room with shortness of
breath and fatigue. He is also very pale. Two days earlier he was given
penicillin for an infection. He had penicillin previously without problems
and stated that he had “no allergy” to penicillin. Laboratory testing shows
that antibodies to penicillin are present in the patient’s serum and that he
is breaking down his own red blood cells. He is diagnosed with immune
hemolytic anemia. The patient has which type of hypersensitivity
reaction?
(A) Type I
(B) Type II
(C) Type III
(D) Type IV (DTH)
4. Which one of the following cell types expresses receptors for IgE on its
cell surface that stimulate the cell to mount a response to parasites such as
worms?
(A) T cells
(B) B cells
(C) Promonocytes
(D) NK cells
(E) Mast cells
5. Which immunologic test is widely used to precisely enumerate and
collect cells expressing an antigen bound by a fluorescencetagged
monoclonal antibody?
(A) ELISA
(B) Direct immunofluorescence
(C) Western blotting
(D) Fluorescence-activated cell sorting
(E) Indirect immunofluorescence
6. In any given immunoglobulin molecule, the light chains are:
(A) Identical to each other in their antigenic determinants
(B) Identical to each other
(C) Identical to each other except in their hypervariable regions
(D) Of related but different amino acid sequences
(E) Identical to each other except in their overall domain structure
7. Antigen–antibody complexes are phagocytosed more effectively in the
presence of which complement component?
(A) C3a and C5a
(B) C3b
(C) C56789 complex
(D) MBL
(E) Properdin
8. NK cells express a killer immunoglobulin-like receptor, which
recognizes:
(A) MHC class I molecules
(B) MHC class II molecules
(C) Cell adhesion molecules
(D) Glycophospholipid molecules
(E) CD40 molecules
9. A cell that plays a critical role in the innate immune response and kills
virus infected cells is:
(A) T cell
(B) Neutrophil
(C) NK cell
(D) Macrophage
(E) B cell
10. A cytokine that activates cells to express MHC class II antigens and
protects cells from virus replication is:
(A) Interferon-α
(B) IL-6
(C) Interferon-γ
(D) TNF-α
(E) IL-10
11.IgE-mediated histamine release is classified as what type of
hypersensitivity reaction?
(A) Type 1
(B) Type 2
(C) Type 3
(D) Type 4
12.The interaction of a pathogen molecule with its specific TLR directly
results in which of the following?
(A) Presentation of pathogen molecule to helper T cells
 (B) Cell activation and production of cytokines and chemokines
(C) IgG production
(D) Immunoglobulin class switching
(E) Phagocytosis

1. A
2. A
3. B
4. E
5. D
6. B
7. B
8. A
9. C
10. C
11. A
12. B
1. Which statement regarding fungi is correct?
(A) All fungi are able to grow as yeasts and molds.
(B) Although fungi are eukaryotes, they lack mitochondria.
(C) Fungi are photosynthetic.
(D) Fungi have one or more nuclei and chromosomes.
(E) Few fungi possess cell membranes.

2. Which statement regarding fungal growth and morphology is

correct?
(A) Pseudohyphae are produced by all yeasts.
(B) Molds produce hyphae that may or may not be partitioned
with cross-walls or septa.
(C) Conidia are produced by sexual reproduction.
(D) Most yeasts reproduce by budding and lack cell walls.
(E) Most pathogenic dimorphic molds produce hyphae in the
host and yeasts at 30°C.

3. Which statement regarding fungal cell walls is correct?

(A) The major components of fungal cell walls are proteins
such as chitin, glucans, and mannans.
(B) The cell wall is not essential for fungal viability or
survival.
(C) Ligands associated with the cell walls of certain fungi
mediate attachment to host cells.
(D) Fungal cell wall components are the targets for the major
classes of antifungal antibiotics, such as the polyenes and
azoles.
(E) Fungal cell wall components rarely stimulate an immune
response.

4. A 54-year-old man developed a slowly worsening headache followed by

gradual, progressive weakness in his right arm. A brain scan revealed a left
cerebral lesion. At surgery an abscess surrounded by granulomatous material
was found. Sections of the tissue and subsequent culture showed darkly
pigmented septate hyphae indicating phaeohyphomycosis. This infection
may be caused by species of which genus below?
(A) Aspergillus
(B) Cladophialophora
(C) Coccidioides
(D) Malassezia
(E) Sporothrix
5. A 35-year-old man is a farmer in a tropical area of West Africa. He
developed a persistent scaly papule on his leg. Ten months later a new crop of
wart-like purplish scaly lesions appeared. These lesions slowly progressed to a
cauliflower-like appearance. Chromoblastomycosis (chromomycosis) was
diagnosed. Which statement regarding this disease is most correct?
(A) In tissue, the organisms convert to spherical cells that
reproduce by fission and exhibit transverse septations.
(B) The etiologic agents are endogenous members of the mammalian
flora and possess melanized cell walls.
(C) The disease is caused by a single species.
(D) Most infections are systemic.
(E) Most infections are acute and clear spontaneously.

6. A 42-year-old HIV-positive male, originally from Vietnam but now residing

in Tucson, Arizona, presents with a painful ulcerative lesion on his upper lip
(cheilitis). A biopsy was obtained, and the histopathologic slide (hematoxylin
and eosin stain) revealed spherical structures (20–50 μm in diameter) with thick
refractory cell walls. What is the likely disease consistent with this finding?
(A) Infection with Penicillium marneffei
(B) Cryptococcosis
(C) Blastomycosis
(D) Coccidioidomycosis
(E) No diagnostic significance

7. A 47-year-old man with poorly controlled diabetes mellitus developed a

bloody nasal discharge, facial edema, and necrosis of his nasal septum. Culture
of his cloudy nasal secretions yielded Rhizopus species. What is the most
important implication of this finding?
(A) No diagnostic value because this mold is an airborne
contaminant.
(B) Consider treatment for rhinocerebral mucormycosis
(zygomycosis).
(C) Strongly suggestive of ketoacidosis.
(D) Strongly suggestive of HIV infection.
(E) The patient has been exposed to indoor mold contamination.

8. An 8-year-old boy develops a circular dry, scaly, and pruritic lesion on his
leg. What is the diagnostic significance of observing branching, septate,
nonpigmented hyphae in a potassium hydroxide/calcofluor white preparation of
a scraping from this skin lesion?
(A) Chromomycosis
(B) Dermatophytosis
(C) Phaeohyphomycosis
(D) Sporotrichosis
(E) No diagnostic significance

9. Which statement regarding the epidemiology of candidiasis is correct?

(A) Patients receiving bone marrow transplants are not at risk for systemic
candidiasis.
(B) Patients with impaired or low numbers of neutrophils and monocytes are not
at risk for systemic candidiasis.
(C) Patients with any form of diabetes have enhanced resistance to candidiasis.
(D) Patients with AIDS frequently develop mucocutaneous candidiasis, such as
thrush.
(E) Pregnancy lowers the risk of candidal vaginitis.

10. Which statement regarding dermatophytosis is correct?

(A) Chronic infections are associated with zoophilic dermatophytes, such as
Microsporum canis.
(B) Acute infections are associated with zoophilic dermatophytes, such as M
canis.
(C) Chronic infections are associated with anthropophilic dermatophytes, such
as M canis.
(D) Acute infections are associated with anthropophilic dermatophytes, such as
M canis.

11. Which statement regarding the laboratory identification of fungi is correct?

(A) Histoplasma capsulatum typically requires less than 48 hours of incubation
to yield positive cultures from clinical specimens.
(B) Since many saprobic (nonpathogenic) molds resemble dimorphic mycotic
agents in culture at 30°C, the identification of putative dimorphic pathogenic
fungi must be confirmed by conversion to the tissue form in vitro or by the
detection of species-specific antigens or DNA sequence analysis.
(C) Molds are routinely speciated by a battery of physiologic tests, such as the
ability to assimilate various sugars.
(D) A positive germ tube test provides a rapid presumptive identification of
Candida glabrata.
(E) Budding yeast cells and abundant pseudohyphae are typical of Pneumocystis
jiroveci.

12. A 28-year-old female sex worker from southern California complained of

headaches, dizziness, and occasional episodes of “spacing out” during the past 2
weeks. A lumbar puncture revealed reduced sugar, elevated protein, and 450
mononuclear leukocytes per milliliter. She was seropositive for HIV. Her
history is compatible with fungal meningitis due to Cryptococcus neoformans,
Coccidioides posadasii, or a species of Candida. Which one of the following
tests is confirmatory?
(A) Meningitis due to Coccidioides posadasii would be confirmed by a positive
test of the CSF for cryptococcal capsular antigen.
(B) Meningitis due to Cryptococcus neoformans would be confirmed by a
positive test of the CSF for complement fixation antibodies to coccidioidin.
(C) Meningitis due to a species of Candida would be confirmed
by the microscopic observation of oval yeast cells and pseudohyphae in the
CSF.
(D) Meningitis due to Coccidioides posadasii would be confirmed by a positive
skin test to coccidioidin.

13. Which statement about phaeohyphomycosis is correct?

(A) The infection only occurs in immunocompetent patients.
(B) Infected tissue reveals branching, septate nonpigmented hyphae.
(C) The causative agents are members of the normal microbial flora and can be
isolated readily from the skin and mucosa of healthy persons.
(D) Phaeohyphomycosis may exhibit several clinical manifestations, including
subcutaneous or systemic disease, as well as sinusitis.
(E) Cases rarely respond to treatment with itraconazole.

14. A 37-year-old male with AIDS, currently living in Indianapolis, Indiana,

presented with osteomyelitis of the left hip. A needle biopsy of the bone marrow
was obtained, and the calcofluor white smear revealed a variety of myelogenous
cells, monocytes, and macrophages containing numerous intracellular yeast
cells that were elliptical and approximately 2 × 4 μm. What is the most likely
diagnosis?
(A) Blastomycosis
(B) Candidiasis
(C) Cryptococcosis
(D) Histoplasmosis
(E) No diagnostic significance

15. The potassium hydroxide examination of sputum from a heart transplant

patient with fever and pulmonary infiltrates contains oval budding yeast cells
and pseudohyphae. What is the diagnostic significance?
(A) Aspergillosis
(B) Candidiasis
(C) Hyalohyphomycosis
(D) Phaeohyphomycosis
(E) No diagnostic significance
1. D 8. B 15. E
2. B 9. D 16. D
3. C 10. B
4. B 11. B
5. A 12. C
6. D 13. D
7. B 14. D
 1. An outbreak of mild intestinal distress, sleeplessness, perianal itching, and
anxiety has broken out among preschool children in a private home. The
most likely cause of this condition is
(A) Trichomonas vaginalis
(B) Enterobius vermicularis
(C) Ascaris lumbricoides
(D) Necator americanus
(E) Entamoeba histolytica

2. Chagas disease is especially feared in Latin America because of

its threat to the heart and parasympathetic nervous system and
the lack of an effective drug for the symptomatic later stages.
Your patient is planning to reside in a Venezuelan village for
1–2 years. Which one of the following suggestions would be of
special value for avoiding Chagas disease?
(A) Boil or treat all of your drinking water.
(B) Sleep under a bed net.
(C) Do not keep domestic pets in your house.
(D) Never walk barefoot in the village compound.
(E) Do not eat lettuce or other raw vegetables or unpeeled fruit.

3. A 32-year-old male Peace Corps volunteer recently returned from a 2-year

period working in a war zone in the southern Sudan in Central Africa. He
presents with marked splenic enlargement, nonspecific
hypergammaglobulinemia, and a negative leishmanin skin test (Montenegro
reaction). Mild fevers occur irregularly. The most likely parasitic disease is
(A) Malaria
(B) Cutaneous leishmaniasis
(C) Visceral leishmaniasis
(D) Trypanosomiasis
(E) Filariasis

4. A sexually active 24-year-old woman complains of vaginal itching and a

malodorous purulent vaginal discharge. To verify your tentative diagnosis of
trichomoniasis, you should include which of the following in your workup?
(A) Specific serologic test
(B) Ova and parasite fecal smear
(C) Wet mount of vaginal fluid
(D) Enzyme-linked immunoassay (ELISA) test of serum
(E) Stool culture
5. You are working in a rural medical clinic in China and a 3-year old girl is
brought in by her mother. The child appears emaciated and, upon testing, is
found to have a hemoglobin level of 5 g/dL. Her feet and ankles are swollen,
and there is an extensive rash on her feet, ankles, and knees. The most likely
parasitic infection that causes the child’s condition is
(A) Schistosomiasis
(B) Cercarial dermatitis
(C) Cyclosporiasis
(D) Hookworm infection
(E) Trichuriasis
(F) Ascariasis

6. Pathologic effects of filariae in humans are caused by the adult worms in all
but one species. In this case, the principal damage is caused by the microfilariae
of
(A) Brugia malayi
(B) Mansonella ozzardi
(C) Dracunculus medinensis
(D) Wuchereria bancrofti
(E) Onchocerca volvulus

7. An 18-year-old male complains of abdominal pain, bloating, frequent loose

stools, and loss of energy. He returned a month ago from a 3-week hiking and
camping trek to the Mount Everest Base Camp in Nepal. The trek involved only
high-elevation hiking, since he flew in and out of the 12,000-ft starting point.
Which of the following is an important consideration for the diagnosis?
(A) Exposure to high-level UV radiation
(B) The source and purification of water
(C) The use of insect repellents while hiking
(D) The presence of domestic animals en route
(E) The degree of contact with villagers en route

8. Which one of the following diagnostic tests should be conducted for the
patient in Question 7?
(A) Blood and urine bacteriologic examination
(B) Series of ova and parasite tests and fecal smears
(C) ELISA or hemagglutination serologic tests for malaria
(D) Skin snip microfilarial test
(E) Endoscopic exam for whipworms

9. The parasite most likely to be responsible for the illness of the

patient in Question 7 is
(A) Entamoeba coli
(B) Plasmodium vivax
(C) Trichomonas vaginalis
(D) Naegleria gruberi
(E) Giardia lamblia

10. Several Papua New Guinea villagers known to eat pork during celebrations
were reported to be suffering from an outbreak of epileptiform seizures. One of
the first things you should investigate is
(A) The prevalence of Ascaris infections in the population
(B) The presence of Toxoplasma gondii in cats
(C) The presence of Trypanosoma brucei gambiense in the villagers
(D) The presence of Taenia eggs in the drinking water
(E) The presence of adult Taenia solium in the pigs

11. A 32-year-old male tourist traveled to Senegal for 1 month. During the trip,
he swam in the Gambia river. Two months after his return, he began
complaining of intermittent lower abdominal pain with dysuria. Laboratory
results of ova and parasites revealed eggs with a terminal spine. Which of the
following parasites is the cause of the patient’s symptoms?
(A) Toxoplasma gondii
(B) Schistosoma mansoni
(C) Schistosoma haematobium
(D) Ascaris lumbricoides
(E) Taenia solium

12. What type of specimen was collected for laboratory analysis based on the
answer in the previous question?
(A) Thick blood smear
(B) Stool sample
(C) Urine sample
(D) Blood for serology
(E) Sputum sample

13. A previously healthy 23-year-old woman recently returned from her

vacation after visiting friends in Arizona. She complained of severe headaches,
saw “flashing lights,” and had a purulent nasal discharge. She was admitted into
the hospital with a diagnosis of bacterial meningitis and died 5 days later.
Which of the following parasites should have been considered in the diagnosis?
She had no prior history of travel outside of the United States.
(A) Plasmodium falciparum
(B) Toxoplasma gondii
(C) Strongyloides stercoralis
(D) Entamoeba histolytica
(E) Naegleria fowleri

14. How could the person have acquired the parasite in Question 13?
(A) Ingesting cysts from fecally contaminated drinking water
(B) Eating improperly cooked fish
(C) Eating improperly cooked beef
(D) Walking barefoot in the park
(E) Engaging in unprotected sexual intercourse
(F) Getting bitten by a sandfly
(G) Plunging into a natural hot spring

15. A 37-year-old sheep farmer from Australia presents with upper right
quadrant pain and appears slightly jaundiced. A stool exam was negative for
ova and parasites but a CT scan of the liver reveals a large 14-cm cyst that
appears to contain fluid. Which of the following parasites should be considered?
(A) Toxoplasma gondii
(B) Taenia solium
(C) Taenia saginata
(D) Clonorchis sinensis
(E) Schistosoma mansoni
(F) Echinococcus granulosus
(G) Paragonimus westermani

1. B
2. B
3. C
4. C
5. D
6. E
7. B
8. B
9. E
10. D
11. C
12. C
13. E
14. G
15. F