OpenStax Microbiology Test Bank

OpenStax Microbiology Test Bank Related

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During fibergastroscopy a patient with ulcer disease of the stomach, the mucosal biopsy is taken from the area of an ulcer. Impression smear is prepared from biopsy material and stained by Gram method; the rest of biopsy material is tested for urease activity. Microscopy of the impression smear revealed gram- negative spiral-shaped microorganisms, urease activity test is positive. What bacteria were detected?

  • A. Helicobacter pylori
  • B. Campilobacter jejuni
  • C. Treponema pallidum
  • D. Spirilla minor
Correct Answer: A

Rationale: The correct answer is A: Helicobacter pylori.
Rationale:
1. Gram-negative spiral-shaped microorganisms match the morphology of Helicobacter pylori.
2. Positive urease activity is a characteristic feature of Helicjsonacter pylori.
3. Helicobacter pylori is specifically associated with gastric ulcers and is a common pathogen in the gastrointestinal tract.

Summary:
Choice B, Campilobacter jejuni, is a gram-negative curved bacterium but is not typically associated with gastric ulcers or urease activity. Choice C, Treponema pallidum, is a spirochete bacterium causing syphilis, which is not related to gastric ulcers. Choice D, Spirilla minor, is a generic term for spiral-shaped bacteria and is not a specific pathogen associated with gastric ulcers or urease activity.

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All statements of viral neutralization reaction are true except:

  • A. A key component of the reaction is the complement system involvement
  • B. Specific virus neutralising antibodies block the viral ability to infect cells
  • C. The antibodies are titrated and two serum samples are required
  • D. It is also used to identify newly isolated virus
Correct Answer: A

Rationale: Rationale:
A: Incorrect - The complement system is not directly involved in the viral neutralization reaction.
B: Correct - Specific antibodies neutralize viruses by blocking their ability to infect cells.
C: Incorrect - Antibodies are titrated, but only one serum sample is required for neutralization testing.
D: Incorrect - Viral neutralization is primarily used to measure antibody response, not to identify newly isolated viruses.

A patient with an abscess had Gram-positive cocci in clusters isolated from a wound culture. The organism was catalase-positive and coagulase-positive. What is the likely causative agent?

  • A. Staphylococcus aureus
  • B. Staphylococcus epidermidis
  • C. Streptococcus pyogenes
  • D. Enterococcus faecalis
Correct Answer: A

Rationale: Step-by-step rationale:
1. Gram-positive cocci in clusters suggest Staphylococcus or Streptococcus.
2. Catalase-positive and coagulase-positive narrow it down to Staphylococcus.
3. Staphylococcus aureus is catalase-positive and coagulase-positive.
Therefore, the likely causative agent is Staphylococcus aureus.

Summary:
A: Correct - Staphylococcus aureus fits all the characteristics.
B: Incorrect - Staphylococcus epidermidis is catalase-negative and coagulase-negative.
C: Incorrect - Streptococcus pyogenes is catalase-negative and coagulase-negative.
D: Incorrect - Enterococcus faecalis is catalase-negative and coagulase-negative.

The sepsis is:

  • A. Presence of bacteria in the blood
  • B. Bacteremia, accompanied with chemical and laboratory data for systemic information
  • C. Massive proliferation of toxins in the blood with organ failure
  • D. All of the above
Correct Answer: D

Rationale: The correct answer is D. Sepsis is a systemic response to infection resulting in organ dysfunction.
A: Sepsis can be caused by bacterial infection, but it is not solely defined by the presence of bacteria in the blood.
B: Bacteremia is the presence of bacteria in the blood, which can be a component of sepsis, but sepsis involves a broader systemic response beyond just bacteremia.
C: Sepsis can lead to the release of toxins and organ failure, but sepsis itself is not defined solely by the massive proliferation of toxins.

Therefore, the correct answer is D, as sepsis can involve the presence of bacteria, bacteremia, systemic manifestations, and organ failure.

A unique number that aids in finding additional toxicological information about a specific substance is the

  • A. CAS number.
  • B. atomic number.
  • C. DOT ID number.
  • D. RTECS number.
Correct Answer: D

Rationale: The correct answer is D: RTECS number. The Registry of Toxic Effects of Chemical Substances (RTECS) number is a unique identifier assigned to chemicals and substances known to cause toxicological effects. It aids in accessing detailed toxicological information such as acute toxicity, carcinogenicity, and mutagenicity. The CAS number (A) is a unique numerical identifier for chemical compounds, not specifically for toxicological information. The atomic number (B) is the number of protons in an element's nucleus, unrelated to toxicology. The DOT ID number (C) is used for hazardous materials transportation, not for toxicological information. Therefore, the RTECS number is the correct choice for finding toxicological information about a specific substance.

Which of the following stains is generally used for the diagnosis of tuberculosis?

  • A. Acid-fast stain
  • B. Gram stain
  • C. Negative stain
  • D. Simple stain
Correct Answer: A

Rationale: The correct answer is A: Acid-fast stain. This stain is used for diagnosing tuberculosis due to the unique cell wall composition of Mycobacterium tuberculosis, which resists decolorization by acid-alcohol. This allows the bacteria to retain the primary stain (carbol fuchsin) and appear red under a microscope. Gram stain (B) is not suitable for Mycobacterium tuberculosis as it is gram-positive but does not retain the crystal violet-iodine complex. Negative stain (C) is not used for bacterial identification. Simple stain (D) does not differentiate acid-fast bacteria like Mycobacterium tuberculosis.

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