Microbiology An Introduction 12th Edition Test Bank

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Bacteriological inspection of disinfection quality at a pharmacy revealed a microorganism in an utility room (in the sink). The microorganism has the following properties: mobile nonspore-forming gram- negative bacteria that form capsular substance, grow well on ordinary nutrient media, secrete the blue-green pigment. This microorganism is most likely to be of the following genus:

  • A. Pseudomonas
  • B. Proteus
  • C. Clostridium
  • D. Shigella
Correct Answer: A

Rationale: The correct answer is A: Pseudomonas.
Rationale:
1. Mobile nonspore-forming gram-negative bacteria with a capsule substance indicate Pseudomonas.
2. Pseudomonas grow well on ordinary nutrient media, matching the description.
3. The secretion of a blue-green pigment is a characteristic feature of Pseudomonas.
4. Proteus is a gram-negative bacterium but does not match all the given properties.
5. Clostridium is a gram-positive bacterium that forms spores.
6. Shigella is a gram-negative bacterium but does not have the other characteristics mentioned.
Therefore, based on the properties described, the most likely genus of the microorganism is Pseudomonas.

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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.

A wound smear from a patient revealed Gram-positive cocci arranged in clusters. The culture was catalase-positive and coagulase-positive. What is the causative agent?

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

Rationale: The correct answer is A: Staphylococcus aureus.
1. Gram-positive cocci in clusters suggest staphylococci.
2. Catalase-positive indicates staphylococci since streptococci are catalase-negative.
3. Coagulase-positive further confirms Staphylococcus aureus, distinguishing it from other staphylococci.
Summary: B is incorrect as Streptococcus pyogenes is catalase-negative. C is incorrect as Micrococcus luteus is catalase-negative and coagulase-negative. D is incorrect as Enterococcus faecalis is catalase-negative and coagulase-negative.

In which of the following especially dangerous infections, the respiratory tract is not damaged:

  • A. Tularemia
  • B. Plague
  • C. Anthrax
  • D. Cholera
Correct Answer: D

Rationale: The correct answer is D, Cholera. Cholera is caused by the bacterium Vibrio cholerae and primarily affects the intestines, leading to severe watery diarrhea and dehydration. It does not damage the respiratory tract.

Choice A, Tularemia, affects the respiratory tract and other organs. Choice B, Plague, can cause respiratory symptoms like cough and difficulty breathing. Choice C, Anthrax, can affect the respiratory tract if inhaled in its spore form.

The optochin sensitivity test demonstrates:

  • A. Neisseria gonorrhoeae
  • B. Pneumococcal
  • C. Staphylococci
  • D. Group A streptococci
Correct Answer: B

Rationale: The optochin sensitivity test is used to differentiate Pneumococcal (Streptococcus pneumoniae) from other streptococci. Optochin sensitivity is a characteristic feature of Pneumococcal, as it inhibits its growth. The test involves placing optochin discs on a culture plate and observing the zone of inhibition around the disc for Pneumococcal. Neisseria gonorrhoeae, Staphylococci, and Group A streptococci do not exhibit optochin sensitivity, making them incorrect choices. In summary, the optochin sensitivity test is specific to Pneumococcal, making choice B the correct answer.

Which bacteria are capable of forming spores to survive in harsh environments?

  • A. Bacillus anthracis
  • B. Clostridium botulinum
  • C. Both A and B
  • D. None of the above
Correct Answer: C

Rationale: The correct answer is C (Both A and B) because both Bacillus anthracis and Clostridium botulinum are capable of forming spores to survive in harsh environments. Bacillus anthracis causes anthrax and forms spores that can survive extreme conditions. Clostridium botulinum causes botulism and also forms spores for survival. Option A (Bacillus anthracis) and Option B (Clostridium botulinum) are incorrect on their own because they only represent one of the bacteria capable of forming spores. Option D (None of the above) is incorrect because it disregards the fact that both bacteria can form spores.

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