Microbiology An Introduction 12th Edition Test Bank

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A bacteriological laboratory has received smears from the sputum of a patient with a chronic pulmonary disease. Microscopical examination of the smears stained by the Ziehl-Neelsen technique revealed red bacilli. What property of the tuberculosis bacillus has shown itself?

  • A. Acid resistance
  • B. Alkali resistance
  • C. Alcohol resistance
  • D. Capsule formation
Correct Answer: A

Rationale: The correct answer is A: Acid resistance. The Ziehl-Neelsen staining technique is specifically used to detect acid-fast bacteria like Mycobacterium tuberculosis, which is resistant to acid decolorization. This property allows the tuberculosis bacillus to retain the stain even after exposure to acid-alcohol, appearing red under the microscope.

Explanation of incorrect choices:
B: Alkali resistance - This property is not relevant in the context of Ziehl-Neelsen staining for acid-fast bacteria.
C: Alcohol resistance - While alcohol resistance is related to acid-fastness, it is not the specific property highlighted by Ziehl-Neelsen staining.
D: Capsule formation - Capsule formation is a different characteristic and not directly related to the staining behavior of acid-fast bacteria in the Ziehl-Neelsen technique.

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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.

The complex of all biological processes/mechanisms responsible for the state of steady internal, physical and chemical conditions in the living systems and defense against all foreign agents is knows as:

  • A. infection
  • B. homeostasis
  • C. immunity
  • D. commensalism
Correct Answer: B

Rationale: The correct answer is B: homeostasis. Homeostasis refers to the process by which living organisms maintain a stable internal environment despite external changes. It involves various biological processes and mechanisms that regulate factors such as temperature, pH, and nutrient levels within narrow limits. This is crucial for the proper functioning of cells, tissues, and organs.

Now, let's analyze the other choices:
A: Infection - Infection refers to the invasion and multiplication of harmful microorganisms in the body, leading to illnesses. It is not the correct answer as it does not encompass the overall maintenance of internal conditions.
C: Immunity - Immunity is the body's ability to resist and fight off infections. While immunity is related to defense against foreign agents, it does not fully capture the concept of maintaining internal stability.
D: Commensalism - Commensalism is a type of symbiotic relationship between different species where one benefits without harming the other. It is not related to the overall regulation of

Bacteriophages reproduce by:

  • A. Division
  • B. Mitosis
  • C. Meiosis
  • D. None of them
Correct Answer: D

Rationale: Bacteriophages are viruses that infect bacteria, not living organisms. They do not reproduce through division, mitosis, or meiosis because they lack the cellular machinery for these processes. Instead, bacteriophages replicate by inserting their genetic material into a host bacterium and hijacking its cellular machinery to produce new viral particles. Therefore, the correct answer is D - None of them. Division and mitosis involve cellular division in living organisms, while meiosis is a specialized process for sexual reproduction in eukaryotic organisms, none of which apply to bacteriophages.

Which bacteria are capable of producing exotoxins?

  • A. Clostridium tetani
  • B. Staphylococcus aureus
  • C. Escherichia coli
  • D. All of the above
Correct Answer: D

Rationale: The correct answer is D: All of the above. Clostridium tetani, Staphylococcus aureus, and Escherichia coli are all capable of producing exotoxins. Exotoxins are proteins released by bacteria that can cause damage to the host. Clostridium tetani produces tetanospasmin, causing tetanus. Staphylococcus aureus produces toxins like enterotoxin and toxic shock syndrome toxin-1. Escherichia coli can produce Shiga toxin and heat-labile toxin. Therefore, all three bacteria listed can produce exotoxins, making choice D the correct answer. Choices A, B, and C are incorrect as they do not encompass all the bacteria capable of producing exotoxins.

An example of selective media is:

  • A. McConkey agar
  • B. Bordet Gengou agar
  • C. Peptone water
  • D. None of the above
Correct Answer: A

Rationale: The correct answer is A: McConkey agar. Selective media selectively inhibit the growth of certain organisms while allowing others to grow. McConkey agar contains crystal violet and bile salts that inhibit the growth of Gram-positive bacteria, making it selective for Gram-negative bacteria. Choices B and C are not selective media, as they do not specifically inhibit the growth of certain types of bacteria. Choice D is incorrect as McConkey agar is indeed an example of selective media.

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