Microbiology An Introduction 12th Edition Test Bank

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A 32-year-old patient undergoing dental examination was found to have some rash-like lesions resembling secondary syphilis in the oral cavity. The patient was referred for the serological study with the purpose of diagnosis confirmation. In order to detect antibodies in the serum, living Treponema were used as diagnosticum. What serological test was performed?

  • A. Immobilization
  • B. Passive hemagglutination
  • C. Precipitation
  • D. Complement binding
Correct Answer: B

Rationale: The correct answer is B: Passive hemagglutination. In this test, red blood cells coated with Treponema antigens agglutinate in the presence of patient's serum antibodies. This indicates the presence of antibodies against Treponema, confirming the diagnosis.

A: Immobilization test uses live Treponema to detect specific antibodies, but it is not commonly used for syphilis diagnosis.
C: Precipitation test is not commonly used for syphilis diagnosis.
D: Complement binding test is not specific for syphilis and is used more for autoimmune diseases.

Therefore, passive hemagglutination is the most appropriate serological test in this case due to its specificity and relevance to the presentation of the patient.

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The neonatal infection referred to as “sticky eye†is caused by:

  • A. Streptococcus
  • B. herpes simplex
  • C. Staphylococcus
  • D. Escherichia
Correct Answer: C

Rationale: The correct answer is C: Staphylococcus. Staphylococcus is a common bacteria that can cause neonatal conjunctivitis, also known as "sticky eye." Staphylococcal conjunctivitis presents with symptoms like eye redness, discharge, and swelling. Streptococcus (choice A) typically causes throat infections, herpes simplex (choice B) causes genital or oral sores, and Escherichia (choice D) is a bacteria commonly found in the gastrointestinal tract and is not typically associated with neonatal conjunctivitis. Therefore, the most likely pathogen causing "sticky eye" in newborns is Staphylococcus.

Botulism agent causes severe food toxicoinfection. Point out the most characteristic morphologic feature of botulism agent.

  • A. Gram-positive spore-forming bacilli with subterminal spore
  • B. Thick gram-positive non-sporeforming bacilli
  • C. Gram-positive spore-forming bacilli with terminal spore
  • D. Thin mobile spore-forming bacilli with central spore
Correct Answer: B

Rationale: The correct answer is B: Thick gram-positive non-sporeforming bacilli. In botulism, the causative agent, Clostridium botulinum, is a thick gram-positive bacilli that does not form spores. This is a key characteristic morphologic feature.

A: Gram-positive spore-forming bacilli with subterminal spore - This is incorrect as Clostridium botulinum does not have subterminal spores.
C: Gram-positive spore-forming bacilli with terminal spore - Incorrect because Clostridium botulinum does not form spores.
D: Thin mobile spore-forming bacilli with central spore - Incorrect because Clostridium botulinum is not thin, mobile, or spore-forming.

In summary, the most characteristic morphologic feature of the botulism agent is being thick, gram-positive, and non-sporeforming, making choice B the correct answer.

Which of these is not a factor counteracting the mechanisms of the immune system:

  • A. Antigenic heterogeneity
  • B. Antigenic mimicry
  • C. Synthesis of IgA proteases
  • D. Hyaluronidase synthesis
Correct Answer: D

Rationale: The correct answer is D: Hyaluronidase synthesis. Hyaluronidase is an enzyme produced by some pathogens to break down hyaluronic acid in the extracellular matrix, aiding their spread. This action does not directly counteract the immune system's mechanisms. Antigenic heterogeneity and mimicry can evade immune recognition. IgA proteases degrade IgA antibodies, impairing mucosal immunity. Therefore, D is the only choice not directly involved in counteracting the immune system.

The eukaryotes known for the presence of a macronucleus and a micronucleus are:

  • A. algae
  • B. fungi
  • C. protozoans
  • D. slime molds
Correct Answer: C

Rationale: The correct answer is C: protozoans. Protozoans are eukaryotic organisms that possess both a macronucleus, responsible for general cell functions, and a micronucleus, involved in genetic processes like reproduction. Algae (choice A) typically have a single nucleus, fungi (choice B) lack distinct macronucleus and micronucleus structures, and slime molds (choice D) do not have the same nucleus organization as protozoans. Thus, protozoans are the only group among the choices that exhibit the specific characteristics of having both a macronucleus and a micronucleus.

The correct statement is:

  • A. Bacteria synthesize an identical enzyme set
  • B. Bacteria synthesize enzymes with various nature and action
  • C. Bacteria and viruses synthesize a similar set of enzymes
  • D. Viruses are distinguished by a wider range of enzymes than bacteria
Correct Answer: B

Rationale: The correct answer is B because bacteria synthesize enzymes with various nature and action. This is true because bacteria can produce a wide range of enzymes to carry out different functions such as metabolism, cell wall synthesis, and nutrient acquisition. Option A is incorrect because bacteria do not synthesize identical enzyme sets due to their diverse functions. Option C is incorrect as bacteria and viruses have distinct enzyme profiles. Option D is incorrect as viruses typically have a narrower range of enzymes compared to bacteria. Therefore, the variability in enzyme types and actions produced by bacteria supports the correctness of option B.

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