NBDE Microbiology and Pathology 2

Question 1

Which virulence factor of Streptococcus mutans is most responsible for its adhesion to smooth tooth surfaces?

Accepted Answer

Glucosyltransferase (GTF)

Answer

Glucosyltransferase synthesizes water-insoluble glucans that mediate S. mutans adhesion to smooth enamel surfaces.

Question 2

A patient presents with white plaques on the buccal mucosa that can be wiped off, leaving a red, bleeding base. The most likely causative organism is:

Accepted Answer

Candida albicans

Answer

Pseudomembranous candidiasis (thrush) presents as removable white plaques caused by Candida albicans overgrowth.

Question 3

The Gram-negative anaerobe most strongly associated with adult periodontitis is:

Accepted Answer

Porphyromonas gingivalis

Answer

Porphyromonas gingivalis is a keystone pathogen in chronic periodontitis, producing gingipains that destroy periodontal tissue.

Question 4

A biopsy of a submandibular mass shows 'sulfur granules' surrounded by neutrophils. The causative organism is best described as:

Accepted Answer

Filamentous Gram-positive bacterium

Answer

Actinomyces israelii, a filamentous Gram-positive bacterium, forms sulfur granules characteristic of cervicofacial actinomycosis.

Question 5

Which type of hypersensitivity reaction is responsible for the pathogenesis of contact stomatitis from dental materials?

Accepted Answer

Type IV (delayed-type)

Answer

Contact stomatitis from dental materials (e.g., nickel, eugenol) is mediated by T-lymphocytes in a Type IV delayed hypersensitivity reaction.

NBDE - National Board Dental Examination Practice Test

NBDE - National Board Dental Examination Practice Test

NBDE Microbiology and Pathology 2