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Free Bacteriology MCQs with Answers

167 Bacteriology MCQs from Microbiology, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

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167 questions · page 9 of 9

161. Endotoxin have all but one of the properties given below_______________?

  • A. Produced by gram negative bacteria
  • B. Produced by gram positive bacteria
  • C. Not secreted outside the cell
  • D. Cannot be toxoided

Explanation: Endotoxin is the lipopolysaccharide component of the outer membrane of Gram-negative bacteria, and it is usually released when cells break…

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Correct answer: Produced by gram positive bacteria

162. Toxic shock syndrome is due to the following virulence factor_____________?

  • A. M protein
  • B. Pyrogenic exotoxin
  • C. Streptolysin 0
  • D. Carbohydrate cell wall

Explanation: Toxic shock syndrome is caused by a superantigenic pyrogenic exotoxin, especially TSST-1 produced by Staphylococcus aureus.

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Correct answer: Pyrogenic exotoxin

163. The difference between gram positive and negative bacteria lies in their_______________?

  • A. cell wall
  • B. cell membrane
  • C. Nuclear material
  • D. Mesosomes

Explanation: The major structural difference is in the cell wall: Gram-positive bacteria have a thick peptidoglycan layer, whereas Gram-negative…

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Correct answer: cell wall

164. The specific test for Treponema pallidum is___________?

  • A. VDRL
  • B. Kahn's test
  • C. TPHA
  • D. Widal test

Explanation: TPHA detects antibodies specifically directed against Treponema pallidum and is therefore a treponemal test.

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Correct answer: TPHA

165. Bacteria reproduce mainly by______________?

  • A. Budding
  • B. Binary fission
  • C. Sporing
  • D. Bacterial components produced by host cells

Explanation: Most bacteria reproduce asexually by binary fission, in which the chromosome replicates and one cell divides into two genetically similar…

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Correct answer: Binary fission

166. An oxidase-positive, gram-negative rod which produces a bluish-green pigment has been grown in culture from a swab obtained from an infected burn wound. This organism is susceptible to gentamicin, ticarcillin and tobramicin, but resistant to all the other antibiotics which of the following organisms is it likely to be ?

  • A. Escherichia coli
  • B. Klebsiella pnemoniae
  • C. Proteus miribilis
  • D. Pseudomonas aeruginosa

Explanation: Pseudomonas aeruginosa is an oxidase-positive Gram-negative rod that produces the characteristic blue-green pigment pyocyanin and commonly…

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Correct answer: Pseudomonas aeruginosa

167. The causative organism of syphilis is___________?

  • A. Borrelia burgolorferi
  • B. Chalamydia trachomatis
  • C. Leptospira interrogans
  • D. Treponema pallidum

Explanation: Syphilis is caused by Treponema pallidum, a motile spirochaete transmitted mainly through sexual contact.

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Correct answer: Treponema pallidum
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