Microbiology Subject Review

Question 1

Why is it difficult to develop vaccines against rhinovirus (common cold)?

a. It is more beneficial to risk infection than experience the vaccine side effects.

b. There are too many viral subtypes, making design of vaccines difficult.

c. Vaccines developed for rhinoviruses are too toxic for administration.

d. Viruses hide within tissues to avoid detection by the immune system.

Answer 1

b. There are too many viral subtypes, making design of vaccines difficult.

Question 2

Case:
Antiviral agents are a class of drugs used specifically for treating viral infections rather than bacterial ones. Most antivirals are used for specific viruses, while a broad-spectrum antiviral is effective against a wide range of viruses. Even with the development of numerous antiviral medications, viruses are often difficult to treat because of their high mutation rates and containment within the host cell for most of their lives.

A 60-year-old man with a known history of Parkinson’s disease is to receive treatment for the Influenza A virus. He is given a drug that is useful against Parkinson’s disease as well as for prophylaxis against influenza.

Question:
The drug given most likely has which of the following mechanisms of action?

a. It prevents entry and penetration of the virus

b. It prevents uncoating of the virus

c. It prevents replication of the virus

d. It prevents assembly of newly synthesized virus particles

e. It prevents release of the newly synthesized virus

Answer 2

b. It prevents uncoating of the virus

Question 3

A siderophore is a molecule produced by bacteria that chelates (binds) to and facilitates uptake of iron. The iron-bound siderophore binds to transport receptors on the surface of the bacteria for transport into the cell. Iron is also essential for the host, where it is often bound to a carrier protein (such as hemoglobin or transferrin). Bacterial siderophores compete with the host for soluble iron. How can this host-pathogen tug-of-war for iron be used against the invading bacteria?

a. Antibiotic-siderophore conjugate

b. Dose of antibodies that bind to transferrin

c. Iron supplement during bacterial infection

d. Large dose of an iron chelator

Answer 3

a. Antibiotic-siderophore conjugate

Question 4

What has a similar pathology to Pseudomonas aeruginosa and generally causes infections of burns, wounds, and lungs?

a. Burkholderia cepacia

b. Escherichia coli

c. Staphylococcus aureus

d. Streptococcus pyogenes

Answer 4

a. Burkholderia cepacia

Question 4

Which of the following microorganisms is associated with the ingestion of inappropriately cooked pork?

a. Taenia saginata

b. Clostridium tetani

c. Diphyllobothrium latum

d. Trichinella spiralis

Answer 4

d. Trichinella spiralis

Question 5

An unknown bacteria was inoculated onto Mannitol salt agar. After a 24-hour incubation period, growth occurred and the red media turned yellow. To what species does this sample most likely belong?

a. Escherichia coli

b. Pseudomonas aeruginosa

c. Staphylococcus aureus

d. Staphylococcus epidermidis

Answer 5

c. Staphylococcus aureus

Question 6

Parasites (organisms that live on or in a host) gain nutrients at the expense of the host, and certain species can cause a significant burden of disease in tropic/subtropic regions and temperate climates. What parasitic disease causes the most deaths globally?

a. Chagas disease

b. Leishmaniasis

c. Malaria

d. Schistosomiasis

Answer 6

c. Malaria

Question 7

Case:
A 4-year-old child presents to urgent care with fever and sore throat. Physical exam reveals painful vesicular lesions around the lips and mouth. The mother first noticed the lesions yesterday when she picked the child up from daycare. The patient is treated with oral acyclovir, and the lesions ulcerate and resolve.

Question:
What describes the most likely viral pathogen?

a. Double-stranded DNA; enveloped

b. Double-stranded DNA; non-enveloped

c. Single-stranded RNA; enveloped

d. Single-stranded RNA; non-enveloped

Answer 7

a. Double-stranded DNA; enveloped

Question 8

Through which route does tapeworm infection occur?

a. Contact with pet saliva or feces

b. Ingestion of contaminated food

c. Inhalation of aerosolized body fluids

d. Sexual activity

Answer 8

b. Ingestion of contaminated food

Question 9

Case:
A 13-year-old boy presents in the ED with fever, tender joints, and rapid heartbeat. His mother says he has been sick with a sore throat, which she thought was a cold; now she is concerned it may actually be the flu. Rapid strep test and flu test in the ED are both negative. The physician assistant finds a rash with pink rings and a clear center, orders an Antistreptolysin O antibody test and EKG, and gives the patient penicillin and a round of steroids. The lab test shows a high level of antibodies against Streptococcus.

Question:
What organism is the most likely pathogen?

a. Escherichia coli

b. Staphylococcus aureus

c. Streptococcus pyogenes

d. Streptococcus viridans

Answer 9

c. Streptococcus pyogenes

Question 10

What is an FDA-approved medical application of a product derived from Clostridium botulinum?

a. Eradication of bacteria from food for infants and immunocompromised people

b. Immunogenic vaccine against anthrax species

c. Paralytic to improve muscle spasm associated with neurological condition

d. Restoration of the normal gastrointestinal bacterial flora after antibiotic use

Answer 10

c. Paralytic to improve muscle spasm associated with neurological condition

Question 11

Case:
A 38-year-old man presents with difficulties walking correctly and visual disturbances. Physical examination reveals a broad-based ataxic gait and a positive Romberg sign, which is indicative of neuropathy affecting proprioception.

Question:
What is the most likely diagnosis?

a. Congenital syphilis

b. Primary syphilis

c. Secondary syphilis

d. Tertiary syphilis

Answer 11

d. Tertiary syphilis

Question 12

A 4-year-old boy presents with profuse watery diarrhea and signs of dehydration. What is the pathogenesis of the most likely causative agent?

a. Inactivating protein synthesis

b. Increasing fluid secretion

c. Inhibiting phagocytic ability

d. Inhibiting the release of neurotransmitter

Answer 12

b. Increasing fluid secretion

Question 13

Case:
A 26-year-old man presents with fever of 101°F, dry cough, night sweats, fatigue, muscles aches, and decreased appetite for the past 4 days. He has a history of chronic hepatitis B. He does not take any medications, does not recall any sick contacts, and has not been to the hospital for 3 years. He traveled to the Great Lakes last month and participated in various outdoor activities. Potassium hydroxide preparation of sputum showed a round organism with a doubly refractile wall and a single broad-based bud.

Question:
What organism is the most likely cause of infection?

a. Blastomyces dermatitidis

b. Cryptococcus neoformans

c. Francisella tularensis

d. Mycobacterium tuberculosis

Answer 13

a. Blastomyces dermatitidis

Question 14

A non-compliant HIV-positive male patient has been reporting a stiff neck and a severe headache. The headache was initially lessened by analgesics, but the analgesics are no longer effective. His current CD4+ count is 180/mm3. He is not on any prophylactic drugs. What is the most likely causative agent?

a. Aspergillus fumigatus

b. Candida albicans

c. Cryptococcus neoformans

d. Malassezia furfur

Answer 14

c. Cryptococcus neoformans

Question 15

A patient presents with loss of appetite, nausea, and persistent mucoidal liquid stools. The patient states they have recently been treated for a bacterial infection using multiple antibiotics. It can be assumed the patient is suffering from an infection from the over-colonization of what bacterial species?

a. Bacillus lentus

b. Clostridioides difficile

c. Escherichia coli

d. Shigella dysenteriae

Answer 15

b. Clostridioides difficile

Question 16

Case:
A 29-year-old woman in her second trimester of pregnancy presents to the clinic with vaginal discharge. She reports 2 days of gray-white discharge and a fishy odor. She denies vaginal pruritus or dysuria, but exam reveals mild vulvar irritation. Wet mount of the discharge shows the attached. Refer to the image.

Question:
What would be the most appropriate treatment for this patient?

a. Metronidazole

b. Fluconazole

c. Doxycycline

d. Ceftriaxone

Answer 16

a. Metronidazole

Question 17

A 26-year-old female counselor presents with 2 days of profuse diarrhea and fever. She reports she recently completed a week-long course of antibiotics for an upper respiratory tract infection but takes no other medications. Stool antigen testing for Clostridioides difficile toxin A/B is positive. What contributed most to her diarrheal infection?

a. Consumption of undercooked beef

b. Eradication of native gastrointestinal bacteria

c. Recent travel to Mexico

d. Surreptitious proton pump inhibitor (PPI) use

Answer 17

b. Eradication of native gastrointestinal bacteria

Question 18

What type of progression of human immunodeficiency virus (HIV) is the most rapid and is seen in untreated patients?

a. Expedient

b. Moderate

c. Prolonged

d. Variable

Answer 18

a. Expedient

Question 19

Which of the below pathogens appear to share virulence characteristics with enteroinvasive Escherichia coli suggestive of a shared intermediate between the organism and E. coli?

a. Haemophilus influenzae

b. Neisseria gonorrhoeae

c. Pseudomonas aeruginosa

d. Shigella

Answer 19

d. Shigella

Question 20

Case:
“During the domestication of soybean, the size and weight of seeds have been enhanced by human selection…although an increased photosynthetic capacity could have provided more carbon (Richards, 2000), we hypothesize that the capacity of Biological Nitrogen Fixation (which occurs in a special organ within the seed) was also enhanced during the domestication of soybean.”

Question:
According to the above statement, what effect has human selection had on the internal stores of carbon and nitrogen within soybean seeds?

a. Stores of carbon increased and nitrogen increased.

b. Stores of carbon increased and nitrogen did not increase.

c. Stores of carbon did not increase and nitrogen increased.

d. Stores of carbon did not increase and nitrogen did not increase.

Answer 20

d. Stores of carbon did not increase and nitrogen did not increase.

Question 20

Why might a patient with Capnocytophaga infection need urgent cardiac surgery?

a. Atrial fibrillation

b. Endocarditis

c. Heart failure

d. Tachycardia

Answer 20

b. Endocarditis

Question 21

Pseudomonas aeruginosa is a difficult nosocomial infection to control due to the nature of the bacteria’s glycocalyx. Which type of glycocalyx does this Pseudomonas have?

a. Capsule

b. Peptidoglycan

c. S-Layer

d. Slime layer

Answer 21

a. Capsule

Question 22

A 6-month-old male infant who has suffered from frequent infections caused by Neisseria meningitidis is found to have a deficiency in complement components C6 and C7. What component of innate immunity depends on the presence of C6 and C7?

a. Attraction of white blood cells through chemotaxis

b. Binding to the Fc portion of IgM and IgG antibodies

c. Forming the complement membrane attack complex

d. Opsonization of invading pathogens

Answer 22

c. Forming the complement membrane attack complex

Question 23

What is the most likely source of infection with hepatitis B virus?

a. Asymptomatic carrier

b. Definitive host

c. Intermediate host

d. Passive carrier

Answer 23

a. Asymptomatic carrier

Question 23

What is the most critical factor in the spread of nosocomial infections involving Staphylococcus aureus?

a. Disinfectants are generally ineffective against Gram-positive bacteria.

b. Patients may be immuno-suppressed or have new portals of entry.

c. Spread occurs through foodborne transmission in hospital cafeterias.

d. Cooling towers for hospital heating and ventilation towers are natural reservoirs.

Answer 23

b. Patients may be immuno-suppressed or have new portals of entry.

Question 24

What agent would show efficacy against methicillin-resistant Staphylococcus aureus (MRSA)?

a. Ampicillin (Omnipen)

b. Cephalexin (Keflex)

c. Ciprofloxacin (Cipro)

d. Vancomycin (Vancocin)

Answer 24

d. Vancomycin (Vancocin)

Question 25

What is the transfer of genetic material from one cell to another through cell-to-cell connections?

a. Transformation

b. Conjugation

c. Electroporation

d. Transduction

Answer 25

b. Conjugation

Question 26

What is the most suitable habitat for the dermatophytes that cause dermatophytosis?

a. A burgeoning tropical city

b. A densely populated desert city

c. A frigid tundra with sparse wildlife

d. An uninhabited tropical island

Answer 26

a. A burgeoning tropical city

Question 27

Which of the following examples of gene editing is prohibited in the United States?

a. Gene for cystic fibrosis in the pneumocytes of an adult

b. Gene for Huntington’s disease in neurons of an elderly patient

c. Gene for sickle cell anemia in the hematopoietic stem cells of an infant

d. Gene for Tay-Sachs disease in the pluripotent stem cells of an embryo

Answer 27

d. Gene for Tay-Sachs disease in the pluripotent stem cells of an embryo

Question 28

There is an outbreak of disease caused by a virus in Liberia, West Africa. Patients present with symptoms including vomiting of blood and bleeding from the eyes, skin, and gastrointestinal tract. The mortality rate of this disease is more than 70%, and it is transmitted by contact with blood and body fluids. What virus is the most likely cause of this disease?

a. Dengue virus

b. Ebola virus

c. West Nile encephalitis

d. Yellow fever

Answer 28

b. Ebola virus

Question 29

Case:
A 17-year-old boy presents to urgent care with 2 days of dysuria and urethral discharge. Gram stain from a urethral swab shows the following. Refer to the image.

Question:
What organism is most likely responsible for this patient’s symptoms?

a. Neisseria gonorrhoeae

b. Chlamydia trachomatis

c. Herpes simplex virus

d. Treponema pallidum

Answer 29

a. Neisseria gonorrhoeae

Question 30

What is the primary cause of symptoms associated with scalded skin syndrome?

a. Bacterial release of toxin

b. Catalase

c. Coagulase

d. Toxic shock syndrome

Answer 30

a. Bacterial release of toxin

Question 31

Some bacteria have evolved mechanisms to traverse the mucus layer of the intestines to reach epithelial cells. Which of the following is an expected adaptation for this mechanism of infection?

a. Down regulation of proteases targeting host mucins

b. Impediment of flagella

c. Resistance to antimicrobial compounds

d. Susceptibility to digestive enzymes

Answer 31

c. Resistance to antimicrobial compounds

Question 32

The Gram-negative bacterium Neisseria gonorrhoeae, often arranged in pairs, has a round shape. How is it classified?

a. Bacillus

b. Coccus

c. Spirochete

d. Vibrios

Answer 32

b. Coccus

Question 32

Case:
A 65-year-old man presents to the emergency department after 1 day of fevers and chills. He has been in his usual state of health apart from a cough for the last 2 weeks. Bronchial breath sounds and dullness to percussion in the right lower lung field are noted on exam. Chest radiograph reveals lobar consolidation.

Question:
What would be shown by a Gram stain of the organism most likely responsible for this patient’s presentation?

a. Gram-positive cocci in chains

b. Gram-positive diplococci

c. Gram-positive cocci in clusters

d. Gram-negative rods

e. Acid-fast bacteria

Answer 32

b. Gram-positive diplococci

Question 33

Case:
A 51-year-old man with a history of chronic hypertension and type 2 diabetes mellitus poorly controlled with medications presents with nasal discharge, sinus congestion, and headaches. His BMI is 40, and he smoked previously from age 16 to 26. During physical examination, you note mild ptosis, proptosis, and necrotic black lesions on his nasal turbinates. Treatment is initiated immediately.

Question:
What fungal species do you expect to see on culture?

a. Candida

b. Cryptococcus

c. Naegleria

d. Rhizopus

Answer 33

d. Rhizopus

Question 34

An otherwise healthy 65-year-old man was in a car accident and broke several ribs on the left side. Approximately 12 days later, he developed a painful well-circumscribed vesicular rash over the left rib cage that persisted for several weeks. What most likely caused the rash?

a. Primary infection with Epstein-Barr virus

b. Primary infection with varicella zoster virus

c. Reactivation of latent Epstein-Barr virus

d. Reactivation of latent varicella zoster virus

Answer 34

d. Reactivation of latent varicella zoster virus

Question 35

A patient presents with large flattened plaques on the face and trunk with raised red edges and dry pale hairless centers. What condition is the most likely cause of infection?

a. Lepromatous leprosy

b. Primary tuberculosis

c. Reactivation tuberculosis

d. Tuberculoid leprosy

Answer 35

d. Tuberculoid leprosy

Question 36

Aerodigestive trematodiasis is contracted through which mechanism?

a. Bites from infected family pets that act as natural reservoirs

b. Consumption of freshwater plants contaminated with infected feces

c. Ingestion of infected raw beef and pork products

d. Swimming in infected freshwater areas

Answer 36

b. Consumption of freshwater plants contaminated with infected feces

Question 37

Case:
A 32-year-old man presents with fever, headache, dry cough, and myalgias for the past 2 days. The patient denies having his seasonal vaccine this year.

Question:
What virus type is probably causative of the patient’s symptoms?

a. Enveloped double-stranded DNA virus

b. Enveloped single-stranded RNA virus

c. Naked double-stranded DNA virus

d. Naked single-stranded RNA virus

Answer 37

b. Enveloped single-stranded RNA virus

Question 38

Viruses are microorganisms that contain what?

a. Cell walls and peptidoglycan

b. Cilia and flagella

c. Nucleus and cytoplasm

d. Proteins and genetic material

Answer 38

d. Proteins and genetic material

Question 38

Case:
A 51-year-old man with a history of chronic hypertension and type 2 diabetes mellitus poorly controlled with medications presents for a routine checkup. He has had no problems since his last medical checkup. His BMI is 40, and he smoked previously from age 16 to 26. You recommend he receive the pneumococcal polysaccharide vaccine.

Question:
What risk factor for severe pneumococcal infection warrants receiving the vaccine?

a. Chronic hypertension

b. Diabetes mellitus

c. Obesity

d. Smoking history

Answer 38

b. Diabetes mellitus

Question 39

Arbuscular mycorrhizas help plants capture nutrients (phosphorus, sulfur, nitrogen) and micronutrients from the soil. These fungi do not reproduce sexually and cannot survive without a symbiotic association with plant roots. What type of fungus are these?

a. Ascomycota

b. Chytridiomycota

c. Glomeromycota

d. Zygomycota

Answer 39

c. Glomeromycota

Question 40

What is the most compelling presentation to administer treatment for R. ricketsii infection?

a. Fever

b. Headache

c. History of tick bite

d. Muscle pain

Answer 40

c. History of tick bite

Question 41

Case:
A 40-year-old man presents to the emergency department after being rescued from an apartment fire. The patient is currently sedated and intubated. Oxygen saturation is 96% at room air. He exhibits burns on 70% of his body surface. 3 days later, he develops green film over the burn wounds on his arms. The nurse notes a smell in the room and asks you about the possibility of diabetic ketoacidosis. You decide to take a sample of the green film to the laboratory for culture, sensitivity, and microbial examination and start the patient on empiric antibiotic therapy.

Question:
What antibiotic is the best option?

a. Amoxicillin + clavulanic acid

b. Aztreonam + gentamicin

c. Gentamicin

d. Linezolid

Answer 41

b. Aztreonam + gentamicin

Question 42

Histoplasma capsulatum, the causative agent of histoplasmosis, can be contracted in specific environments, including caves. Why are caves considered at-risk areas for this fungus?

a. This fungus is transmitted by bat droppings.

b. This fungus grows best on limestone.

c. This fungus is killed by sunlight.

d. This fungus thrives in cool environments.

Answer 42

a. This fungus is transmitted by bat droppings.

Question 43

What cellular structure is considered as the “powerhouse of the cell”?

a. Ribosome

b. Mitochondrion

c. Chromosome

d. Microbody

Answer 43

b. Mitochondrion

Question 44

Protein A, made by Staphylococcus aureus, has high affinity to the heavy chain of the constant region of most IgG molecules. Which part of IgG molecules does Protein A bind with the highest affinity?

a. Fab

b. Fc

c. Fv

d. Hinge region

Answer 44

b. Fc

Question 45

The pathology of Escherichia coli depends on the area of colonization; for example, as the source of gastrointestinal illness, it can cause diarrhea. What is an additional manifestation of an E. coli infection?

a. Nose infection

b. Pneumonia

c. Skin and wound infection

d. Urinary tract infection

Answer 45

d. Urinary tract infection