Microbiology An Introduction 12th Edition Test Bank

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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.

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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.

At a bacteriological laboratory animal skins are analyzed by means of Ascoli precipitaion test. What is detected if the reaction is positive?

  • A. Anthrax agent antigens
  • B. Brucellosis agent
  • C. Anaerobic infection toxin
  • D. Plague agent
Correct Answer: A

Rationale: The Ascoli precipitation test is specifically used to detect anthrax agent antigens. The test involves mixing a patient's serum with a solution containing anthrax antigens, leading to precipitation if the antigens are present. Therefore, a positive reaction in this test indicates the presence of anthrax agent antigens. The other choices (B: Brucellosis agent, C: Anaerobic infection toxin, D: Plague agent) are incorrect because the Ascoli precipitation test is not designed to detect these specific agents or toxins.

Infectious process is:

  • A. Clinically manifested disease
  • B. Infectious disease with typical symptoms
  • C. Interrelation between the macro- and micro organism
  • D. Ambulatory form of infection
Correct Answer: C

Rationale: Rationale:
1. Infectious process involves interactions between macro and microorganisms.
2. It is not limited to manifested diseases or typical symptoms.
3. The process can occur without leading to a full-blown infectious disease.
4. Choice C correctly captures the dynamic relationship between different organisms.
Summary:
- A: Incorrect - Infectious process is not solely about clinically manifested diseases.
- B: Incorrect - Not all infectious diseases have typical symptoms.
- D: Incorrect - Ambulatory form is a specific type, not encompassing all infectious processes.

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.

Widal test is used to diagnose

  • A. Syphilis
  • B. Typhoid fever
  • C. AIDS
  • D. Lyme disease
Correct Answer: B

Rationale: The Widal test is used to diagnose typhoid fever caused by the bacteria Salmonella typhi. The test detects antibodies produced in response to the bacteria. Positive results indicate a current or past infection with typhoid fever. Choice A (Syphilis) is incorrect as it is diagnosed using different tests like RPR or TPPA. Choice C (AIDS) is diagnosed with HIV tests like ELISA or Western blot. Choice D (Lyme disease) is diagnosed using tests like ELISA or Western blot specific for Borrelia burgdorferi.

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