Micro

Question 1

What is the most sensitive and specific test for diagnosing C. difficile?

Answer 1

NAAT using a PCR

Question 2

A combination of nicotinic and muscarinic blockade is strongly suggestive of which organism?

Answer 2

• Clostridium botulinum toxin
• Diplopa, Dysphagia, and Dysphonia = “3 D’s”

Question 3

Small, ovoid bodies within macrophages is characteristic of which fungus?

Answer 3

Histoplasma capsulatum

Question 4

Hepatosplenomegaly, LAD, pancytopenia and ulcerated lesions on the tongue are very characteristic of disseminated infection by which fungus?

Answer 4

Histoplasma capsulatum

Question 5

How does Dengue Fever most commonly present?

Answer 5

Acute febrile illness w/ HA + retro-orbital pain + joint and muscle pain

Question 6

Which viruses have the capability of undergoing reassortment due to their segmented genomes?

Answer 6

• Bunyaviruses
• Orthomyxoviruses
• Arenaviruses
• Reoviruses

Question 7

What are the clinical manifestations of Tuberculoid Leprosy?

Answer 7

Mild skin plaques –> hypopigmentation, hair follicle loss, and focally decreased sensation

Question 8

Hepatocytes with finely granular, diffusely homogenous, pale eosinophilic cytoplasm aka “ground-glass” is a distinct histopathologic manifestation of which infection?

Answer 8

Hepatitis B due to accumulation of HBsAg

Question 9

Which stage of syphilis is characterized by a maculopapular, bronzing rash that covers the entire body; how is this stage diagnosed?

Answer 9

Secondary syphillis; order RPR which is then confirmed by FTA-ABS

Question 10

A boxcar-shaped, gram-positive rod describes what?

Answer 10

Bacillus anthracis

Question 12

Presence of leukocyte esterase and nitrites in urine are highly sensitive for a UTI caused by what 3 organisms?

Answer 12

Gram-negative –> E. coli, Klebsiella, and Proteus

Question 13

Which infectious agent causes a maculopapular rash that begins on the face before quickly spreading to the trunk and extremities and is also associted with postauricular and occipital LAD?

Answer 13

Rubella (Togavirus) - positive sense ssRNA virus

Question 14

List the 5 most common catalase-positive organisms,

Answer 14

• S. aureus
• Burkholderia cepacia
• Serratia marcescens
• Nocardia
• Aspergillus

Question 15

What is the most common cause of spontaneous gas gangrene (i.e., rapid-onset pain, hemorrhagic bullae, and tissue crepitus); what is the greatest risk factor for infection?

Answer 15

• Clostridium septicum
• Underlying colonic malignancy is the greatest risk factor for infection

Question 16

Which enzyme in prokaryotes has 5’ to 3’ exonuclease activity and functions to remove the RNA primer and replace it with DNA?

Answer 16

DNA polymerase I

Question 17

Which endotoxin from the LPS of gram-negative bacteria is highly toxic and can lead to gram-negative sepsis and endotoxic septic shock; how does this occur?

Answer 17

• Lipid A
• Activates macrophages and granulocytes; causing synthesis of pyrogens such as IL-1, prostaglandins, and inflammatory mediators TNF-alpha and interferon

Question 18

What is the major virulence factor of Haemophilus influenzae type b (Hib)?

Answer 18

Polysaccharide capsule, composed of polyribosylribitol phosphate (PRP)

Question 19

Which fungus has branching at acute angle with septations?

Answer 19

Aspergillus fumigatus

Question 20

What is the MOA of both tracheal cytotoxin and pertussis toxin from Bordetella pertussis?

Answer 20

• Tracheal: directly damages and destroys ciliated epithelial cells = loss of airway protection, subsequnt microaspiration and development of the hallmark paroxysmal cough
• Pertussis: enters cells, activates adenylate cyclase, leading to alterations in cellular signaling that inhibit phagocyte activity

Question 21

What is the characteristic histopathologic finding in the brain of patient with HIV-associated dementia?

Answer 21

Microglial nodules and multinucleated giant cells