McGraw Hill Microbiology Test Bank

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During examination of the patient's oral cavity a dentist noticed deformation of the teeth and a crescent indentation of the upper right incisor. The teeth are undersized, barrel-shaped – tooth cervix is wider than its edge. The patient uses a hearing aid, suffers from visual impairment. What type of syphilis affects teeth in such way?

  • A. Primary
  • B. Early congenital
  • C. Neurosyphilis
  • D. Late congenital
Correct Answer: D

Rationale: The correct answer is D, Late congenital syphilis. This is because the patient presents with Hutchinson's teeth, which are a characteristic feature of late congenital syphilis. Hutchinson's teeth are small, barrel-shaped teeth with a wider cervix and notched incisors. The patient's history of visual impairment and hearing aid use also support the diagnosis of late congenital syphilis, as these are common manifestations of this stage of the disease.

Choice A, Primary syphilis, is incorrect because it typically presents with a painless sore at the site of infection, not dental abnormalities. Choice B, Early congenital syphilis, is incorrect as dental abnormalities in this stage are usually more severe, such as mulberry molars. Choice C, Neurosyphilis, is incorrect as it primarily affects the central nervous system and does not typically present with dental abnormalities.

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In an agar slant, bacterial colonies that appear separate or semiconfluent are referred to as:

  • A. filiform
  • B. echinulate
  • C. beaded
  • D. effuse
Correct Answer: C

Rationale: The correct answer is C: beaded. In an agar slant, beaded colonies appear as separate or semiconfluent, forming small, round colonies with gaps between them. This term accurately describes the appearance of the colonies in this context.

A: Filiform colonies are dense and opaque with smooth edges, not separate or semiconfluent.
B: Echinulate colonies have spiny projections, not the characteristic of separate or semiconfluent growth.
D: Effuse colonies spread out extensively and lack defined borders, unlike the distinct appearance of separate or semiconfluent colonies.

Which bacteria are known for producing toxins that can cause severe gastrointestinal illness?

  • A. Clostridium botulinum
  • B. Vibrio cholerae
  • C. Escherichia coli
  • D. All of the above
Correct Answer: D

Rationale: The correct answer is D, "All of the above." Clostridium botulinum produces botulinum toxin causing botulism, Vibrio cholerae produces cholera toxin leading to severe diarrhea, and certain strains of Escherichia coli produce toxins causing gastrointestinal illness. Therefore, all three bacteria are known for producing toxins that can cause severe gastrointestinal illness. Choices A, B, and C individually represent bacteria known for producing toxins that can cause severe gastrointestinal illness, making them incorrect individual choices.

In order to accurately identify etiology of peptic ulcer disease, polymerase chain reaction (PCR) analysis was performed on gastric biopsy specimen taken from 47-year-old patient. Eventually, the test result was positive for H. pylori. Which of the following was most likely detected in PCR analysis?

  • A. Bacterial DNA
  • B. Bacterial toxin
  • C. H. pylori bacterium itself
  • D. Bacterial enzymes – urease and catalase
Correct Answer: A

Rationale: The correct answer is A: Bacterial DNA. PCR analysis detects specific DNA sequences, so a positive result for H. pylori indicates the presence of the bacterial DNA in the gastric biopsy specimen. This method identifies the genetic material of the bacterium, not the bacterium itself (choice C) or its toxins (choice B). Additionally, PCR does not directly detect bacterial enzymes (choice D) but rather focuses on genetic material for accurate identification. Therefore, in this case, the detection of H. pylori in the PCR analysis points to the presence of bacterial DNA, confirming the etiology of peptic ulcer disease.

The term “infectious process†means “all biological processes carried out after…â€

  • A. The attachment and penetration of microbes into the microorganism
  • B. The attachment and penetration of microbes into the microorganisms regardless of whether or not there is clinical manifestation
  • C. The penetration of microbes into the macroorganism and always manifest clinically
  • D. No correct answer
Correct Answer: B

Rationale: The correct answer is B because the term "infectious process" refers to all biological processes that occur after the attachment and penetration of microbes into the host organism, regardless of whether there are clinical manifestations. This includes the colonization, multiplication, and spread of the microorganisms within the host.

Explanation:
A: Incorrect because it only mentions the attachment and penetration of microbes into the microorganism, missing the subsequent processes.
C: Incorrect because it is too specific, stating that the penetration of microbes always manifests clinically, which is not always the case.
D: Incorrect because there is a correct answer, which is B, as explained above.

Which bacteria produce exotoxins that damage host tissues?

  • A. Clostridium tetani and Bacillus anthracis
  • B. Escherichia coli and Pseudomonas aeruginosa
  • C. Streptococcus pneumoniae and Listeria monocytogenes
  • D. Salmonella typhi and Mycobacterium tuberculosis
Correct Answer: A

Rationale: The correct answer is A: Clostridium tetani and Bacillus anthracis. Both bacteria produce exotoxins that damage host tissues. Clostridium tetani produces tetanospasmin, which causes muscle rigidity in tetanus. Bacillus anthracis produces anthrax toxins, leading to tissue damage and systemic effects.

Explanation:
- Choice B (Escherichia coli and Pseudomonas aeruginosa) primarily cause infections through other mechanisms and do not produce exotoxins that damage host tissues.
- Choice C (Streptococcus pneumoniae and Listeria monocytogenes) are known for causing infections but not primarily through exotoxins that damage host tissues.
- Choice D (Salmonella typhi and Mycobacterium tuberculosis) cause diseases through different mechanisms and do not produce exotoxins that directly damage host tissues.

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