MCQs on Oral Microbiology:

By | July 23, 2024
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  1. Which of the following bacteria is most commonly associated with dental caries? A) Streptococcus mutans B) Porphyromonas gingivalis C) Actinomyces viscosus D) Fusobacterium nucleatum E) Treponema denticola
  2. A patient presents with acute necrotizing ulcerative gingivitis (ANUG). Which of the following microorganisms is most likely to be involved? A) Streptococcus sanguis B) Actinobacillus actinomycetemcomitans C) Prevotella intermedia D) Fusobacterium nucleatum E) Candida albicans
  3. Which of the following factors is most important for the initial adherence of Streptococcus mutans to tooth surfaces? A) Fimbriae B) Glucosyltransferase C) Lipoteichoic acid D) Extracellular polysaccharides E) Collagenase
  4. A 45-year-old patient with poorly controlled diabetes presents with severe periodontitis. Which of the following microorganisms is most likely to be found in increased numbers in the subgingival plaque? A) Streptococcus mitis B) Actinomyces naeslundii C) Porphyromonas gingivalis D) Streptococcus salivarius E) Veillonella parvula
  5. Which of the following is the primary mechanism by which fluoride prevents dental caries? A) Inhibition of bacterial growth B) Enhancement of enamel remineralization C) Reduction of plaque formation D) Stimulation of salivary flow E) Alteration of tooth morphology
  6. A 30-year-old patient presents with white, removable plaques on the oral mucosa and tongue. Microscopic examination reveals pseudohyphae. Which of the following is the most likely causative agent? A) Actinomyces israelii B) Candida albicans C) Fusobacterium nucleatum D) Aggregatibacter actinomycetemcomitans E) Staphylococcus aureus
  7. Which of the following bacteria is most commonly associated with localized aggressive periodontitis in young adults? A) Porphyromonas gingivalis B) Tannerella forsythia C) Prevotella intermedia D) Aggregatibacter actinomycetemcomitans E) Fusobacterium nucleatum
  8. The ability of Streptococcus mutans to produce large amounts of lactic acid from dietary sugars is primarily due to which of the following enzymes? A) Lactate dehydrogenase B) Pyruvate kinase C) Glucosyltransferase D) Enolase E) Amylase
  9. Which of the following best describes the ecological plaque hypothesis in relation to dental caries? A) Specific pathogens cause caries regardless of environmental conditions B) Environmental changes in the oral cavity lead to a shift in the microbiota, favoring cariogenic bacteria C) Dental plaque is always pathogenic, regardless of its composition D) Caries-causing bacteria are acquired through horizontal transmission from caregivers E) The presence of Streptococcus mutans alone is sufficient to cause caries
  10. A patient presents with angular cheilitis. Which of the following microorganisms is most likely to be involved? A) Porphyromonas gingivalis B) Actinomyces israelii C) Candida albicans D) Treponema denticola E) Streptococcus mutans
  11. Which of the following best describes the role of Fusobacterium nucleatum in the oral microbiome? A) Primary colonizer of tooth surfaces B) Major acid producer in dental plaque C) Bridge organism facilitating co-aggregation of early and late colonizers D) Primary cause of dental caries E) Main etiologic agent of periodontal disease
  12. A patient presents with a painful, ulcerated lesion on the gingiva. Microscopic examination reveals spirochetes. Which of the following is the most likely diagnosis? A) Candidiasis B) Acute necrotizing ulcerative gingivitis (ANUG) C) Aphthous ulcer D) Herpetic gingivostomatitis E) Lichen planus
  13. Which of the following best describes the mechanism by which arginine deiminase system (ADS)-positive bacteria may protect against dental caries? A) Production of bacteriocins B) Increased acid production C) Neutralization of acids through ammonia production D) Enhanced enamel remineralization E) Inhibition of Streptococcus mutans growth
  14. A patient with HIV presents with linear gingival erythema. Which of the following organisms is most likely to be associated with this condition? A) Porphyromonas gingivalis B) Candida albicans C) Actinomyces israelii D) Streptococcus mutans E) Aggregatibacter actinomycetemcomitans
  15. Which of the following best describes the role of quorum sensing in oral biofilm formation? A) Regulation of bacterial cell division B) Coordination of gene expression based on population density C) Inhibition of competing bacterial species D) Enhancement of host immune response E) Promotion of enamel demineralization
  16. A patient presents with halitosis. Which of the following groups of bacteria are most likely responsible for producing volatile sulfur compounds associated with oral malodor? A) Streptococci B) Actinomyces C) Gram-negative anaerobes D) Lactobacilli E) Candida species
  17. Which of the following best describes the role of Streptococcus gordonii in early dental plaque formation? A) Major acid producer B) Primary colonizer providing attachment sites for other bacteria C) Production of hydrogen peroxide to inhibit competing bacteria D) Degradation of salivary proteins E) Induction of inflammatory response
  18. A patient presents with a periodontal abscess. Which of the following bacteria is most likely to be isolated from the purulent exudate? A) Streptococcus mutans B) Actinomyces naeslundii C) Porphyromonas gingivalis D) Streptococcus salivarius E) Veillonella parvula
  19. Which of the following best describes the role of bacterial proteases in periodontal disease progression? A) Enhancement of bacterial adhesion to tooth surfaces B) Degradation of host tissues and immune components C) Production of organic acids leading to tooth demineralization D) Inhibition of competing bacterial species E) Stimulation of osteoblast activity
  20. A patient presents with dental caries and a high Lactobacillus count in saliva. Which of the following best explains the role of Lactobacillus in this scenario? A) Primary initiator of caries B) Secondary invader contributing to lesion progression C) Protective against caries development D) No significant role in caries process E) Main cause of root surface caries
  21. Which of the following best describes the mechanism by which chlorhexidine mouthwash reduces plaque formation? A) Enzymatic breakdown of bacterial cell walls B) Inhibition of bacterial protein synthesis C) Binding to bacterial cell membranes, increasing permeability D) Chelation of calcium ions necessary for bacterial growth E) Stimulation of host immune response against oral bacteria
  22. A patient presents with oral thrush resistant to fluconazole. Which of the following Candida species is most likely responsible? A) Candida albicans B) Candida glabrata C) Candida tropicalis D) Candida krusei E) Candida parapsilosis
  23. Which of the following best describes the role of Aggregatibacter actinomycetemcomitans in localized aggressive periodontitis? A) Production of collagenase B) Secretion of leukotoxin C) Formation of dental calculus D) Inhibition of osteoblast function E) Stimulation of regulatory T cells
  24. A patient presents with denture stomatitis. Which of the following factors is most likely to contribute to the overgrowth of Candida species in this condition? A) Increased salivary pH B) Enhanced mucosal immunity C) Reduced oxygen tension under the denture D) Increased salivary flow E) Presence of Streptococcus mutans
  25. Which of the following best describes the role of bacterial fimbriae in periodontal disease? A) Production of hydrogen sulfide B) Secretion of collagenase C) Adherence to host cells and other bacteria D) Inhibition of neutrophil function E) Stimulation of osteoclast activity
  26. A patient presents with black-pigmented colonies on blood agar from a subgingival plaque sample. Which of the following bacteria is most likely present? A) Streptococcus mutans B) Aggregatibacter actinomycetemcomitans C) Porphyromonas gingivalis D) Actinomyces viscosus E) Fusobacterium nucleatum
  27. Which of the following best describes the mechanism by which arginine-containing toothpastes may help prevent dental caries? A) Direct killing of cariogenic bacteria B) Increasing enamel hardness C) Stimulating salivary flow D) Providing substrate for alkali production by oral bacteria E) Inhibiting glucosyltransferase enzyme
  28. A patient presents with rapidly progressive periodontitis and multiple systemic infections. Which of the following conditions should be suspected? A) HIV infection B) Diabetes mellitus C) Leukocyte adhesion deficiency D) Vitamin C deficiency E) Sjögren’s syndrome
  29. Which of the following best describes the role of Treponema denticola in periodontal disease? A) Initial colonizer of tooth surfaces B) Major producer of extracellular polysaccharides C) Proteolytic activity and invasion of periodontal tissues D) Primary cause of dental caries E) Inhibition of host immune response through biofilm formation
  30. A patient presents with a periapical abscess. Which of the following bacteria is most likely to be involved in this infection? A) Streptococcus mutans B) Porphyromonas gingivalis C) Fusobacterium nucleatum D) Enterococcus faecalis E) Aggregatibacter actinomycetemcomitans
  31. Which of the following best describes the role of matrix metalloproteinases (MMPs) in periodontal disease progression? A) Inhibition of bacterial growth B) Promotion of tissue regeneration C) Degradation of extracellular matrix components D) Stimulation of osteoblast activity E) Enhancement of bacterial adhesion to tooth surfaces
  32. A patient presents with linear gingival erythema. Which of the following is the most likely causative agent? A) Porphyromonas gingivalis B) Candida species C) Actinomyces israelii D) Streptococcus mutans E) Aggregatibacter actinomycetemcomitans
  33. Which of the following best describes the mechanism by which xylitol may prevent dental caries? A) Direct bactericidal effect on Streptococcus mutans B) Inhibition of bacterial acid production C) Stimulation of salivary flow D) Enhancement of enamel remineralization E) Alteration of bacterial gene expression
  34. A patient presents with acute pseudomembranous candidiasis. Which of the following is the most appropriate first-line treatment? A) Fluconazole B) Chlorhexidine mouthwash C) Nystatin D) Miconazole E) Amphotericin B
  35. Which of the following best describes the role of Veillonella species in the oral microbiome? A) Primary colonizer of tooth surfaces B) Major acid producer in dental plaque C) Utilization of lactic acid produced by other bacteria D) Production of hydrogen peroxide E) Degradation of collagen in periodontal tissues
  36. A patient presents with localized juvenile periodontitis. Which of the following virulence factors is most closely associated with the primary etiologic agent of this condition? A) Leukotoxin B) Gingipains C) Fimbriae D) Lipopolysaccharide E) Collagenase
  37. Which of the following best describes the mechanism by which probiotics may benefit oral health? A) Direct killing of pathogenic bacteria B) Stimulation of salivary flow C) Competition for adhesion sites and nutrients D) Inhibition of matrix metalloproteinases E) Enhancement of enamel remineralization
  38. A patient presents with burning mouth syndrome. Which of the following microbial factors is most likely to be associated with this condition? A) Overgrowth of Streptococcus mutans B) Presence of Porphyromonas gingivalis C) Candida albicans infection D) Herpes simplex virus reactivation E) Helicobacter pylori colonization
  39. Which of the following best describes the role of bacterial lipopolysaccharide (LPS) in periodontal disease? A) Direct tissue destruction B) Inhibition of osteoclast activity C) Stimulation of host inflammatory response D) Enhancement of bacterial adhesion to tooth surfaces E) Production of organic acids leading to tooth demineralization
  40. A patient presents with recurrent aphthous stomatitis. Which of the following microbial factors has been most consistently associated with this condition? A) Streptococcus mutans overgrowth B) Candida albicans infection C) Helicobacter pylori colonization D) Herpes simplex virus infection E) Alteration in oral microbiome composition
  41. Which of the following best describes the role of Rothia dentocariosa in the oral cavity? A) Major periodontal pathogen B) Primary cause of dental caries C) Normal oral commensal with potential opportunistic infections D) Key player in halitosis E) Main etiologic agent of angular cheilitis
  42. A patient presents with green staining on the teeth. Which of the following microorganisms is most likely responsible? A) Porphyromonas gingivalis B) Actinomyces viscosus C) Fusobacterium nucleatum D) Aggregatibacter actinomycetemcomitans E) Candida albicans
  43. Which of the following best describes the mechanism by which arginine deiminase (ADS) positive bacteria may protect against dental caries? A) Direct killing of Streptococcus mutans B) Production of hydrogen peroxide C) Generation of ammonia from arginine, raising pH D) Stimulation of salivary flow E) Inhibition of glucosyltransferase enzyme
  44. A patient presents with periodontal disease and rheumatoid arthritis. Which of the following oral bacteria has been most strongly associated with both conditions? A) Streptococcus mutans B) Treponema denticola C) Porphyromonas gingivalis D) Aggregatibacter actinomycetemcomitans E) Fusobacterium nucleatum
  45. Which of the following best describes the role of bacteriocins produced by oral streptococci? A) Promotion of biofilm formation B) Inhibition of competing bacteria C) Degradation of host tissues D) Neutralization of salivary antimicrobial peptides E) Enhancement of acid production
  46. A patient presents with oral hairy leukoplakia. Which of the following is the most likely causative agent? A) Human papillomavirus (HPV) B) Herpes simplex virus (HSV) C) Epstein-Barr virus (EBV) D) Candida albicans E) Porphyromonas gingivalis
  47. Which of the following best describes the role of Streptococcus sanguinis in the oral microbiome? A) Major contributor to dental caries B) Primary cause of periodontal disease C) Early colonizer with potential protective effects against caries D) Main cause of denture stomatitis E) Key player in the development of oral candidiasis
  48. A patient presents with a pericoronitis around a partially erupted wisdom tooth. Which of the following bacteria is most likely to be involved? A) Streptococcus mutans B) Porphyromonas gingivalis C) Actinomyces species D) Aggregatibacter actinomycetemcomitans E) Treponema denticola
  49. Which of the following best describes the mechanism by which Streptococcus mutans contributes to the demineralization of tooth enamel? A) Production of collagenase B) Secretion of leukotoxin C) Generation of lactic acid from fermentable carbohydrates D) Release of lipopolysaccharide E) Stimulation of host inflammatory response
  50. A patient presents with oral manifestations of Crohn’s disease. Which of the following oral microbial changes is most likely to be observed? A) Increase in Streptococcus mutans B) Overgrowth of Candida albicans C) Reduction in oral microbial diversity D) Increase in Porphyromonas gingivalis E) Colonization by Helicobacter pylori.