microbiology chapter 12 test bank

microbiology chapter 12 test bank Related

Review microbiology chapter 12 test bank related questions and content

Your patient is a 22-year-old man. The patient reports that two weeks after unprotected sexual contact, a small ulcer appeared on its penis. The local inguinal lymph nodes are enlarged. Dark field microscopic examination of the ulcer secretions was performed. The test reveals presence of motile, curved spirochete. The most common causative agent of the disease is:

  • A. Chlamydia trachoma's
  • B. Treponema pallidum
  • C. Neisseria gonorrhoeae
  • D. Herpes simplex virus, type 2
Correct Answer: B

Rationale: The correct answer is B: Treponema pallidum. The scenario describes symptoms of primary syphilis, which is caused by Treponema pallidum. The presence of a painless ulcer (chancre) and enlarged inguinal lymph nodes are characteristic of syphilis. Dark field microscopic examination showing motile, curved spirochetes is highly specific for Treponema pallidum.

Incorrect explanations:
A: Chlamydia trachomatis typically causes urethritis or cervicitis, not painless ulcers.
C: Neisseria gonorrhoeae causes gonorrhea, which presents with purulent discharge, not painless ulcers.
D: Herpes simplex virus type 2 causes genital herpes, leading to painful ulcers and vesicles, not painless ulcers seen in syphilis.

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The term bacilli is related to:

  • A. Bacteria that obtain red color in gram staining
  • B. Spore-forming bacteria
  • C. Those having a peptidoglycan up to 1-2%
  • D. None of the above
Correct Answer: B

Rationale: The term bacilli refers to rod-shaped bacteria, typically found in the Gram-positive group. Spore-forming bacteria, such as Bacillus and Clostridium, are characterized by their rod shape. Choice A is incorrect as the color in Gram staining does not define bacilli. Choice C is incorrect as peptidoglycan content does not determine the classification of bacilli. Choice D is incorrect as bacilli do have a specific characteristic. Therefore, the correct answer is B due to the shape and characteristic of spore-forming bacteria.

A sputum sample from a patient with pneumonia revealed Gram-positive cocci in pairs with a capsule. What is the most likely causative agent?

  • A. Streptococcus pneumoniae
  • B. Staphylococcus aureus
  • C. Klebsiella pneumoniae
  • D. Pseudomonas aeruginosa
Correct Answer: A

Rationale: The correct answer is A: Streptococcus pneumoniae. This bacterium is the most likely causative agent for pneumonia in this case due to the presence of Gram-positive cocci in pairs with a capsule, which is a typical characteristic of S. pneumoniae. This pathogen is a common cause of community-acquired pneumonia and is known for its encapsulated morphology. Staphylococcus aureus (B) is a Gram-positive cocci but does not typically present in pairs with a capsule in pneumonia cases. Klebsiella pneumoniae (C) is a Gram-negative bacterium and does not match the description provided. Pseudomonas aeruginosa (D) is a Gram-negative bacterium that is not typically associated with Gram-positive cocci in pneumonia samples.

Immunosuppressive drugs are not used for:

  • A. Organ transplantation
  • B. Measles
  • C. Autoimmune diseases
  • D. Hemolytic disease of the newborn
Correct Answer: B

Rationale: The correct answer is B: Measles. Immunosuppressive drugs are not used for treating viral infections like measles as they target the immune system and can worsen the infection. Organ transplantation requires immunosuppressive drugs to prevent organ rejection. Autoimmune diseases involve an overactive immune response, so immunosuppressive drugs are used to reduce this response. Hemolytic disease of the newborn can be treated with immunosuppressive drugs to prevent the destruction of red blood cells.

Which of the following bacteria is known for causing pneumonia?

  • A. Streptococcus pneumoniae
  • B. Mycobacterium tuberculosis
  • C. Escherichia coli
  • D. Pseudomonas aeruginosa
Correct Answer: A

Rationale: The correct answer is A: Streptococcus pneumoniae. This bacteria is known for causing pneumonia due to its ability to infect the lungs and cause inflammation leading to pneumonia symptoms. It is a common cause of community-acquired pneumonia. Mycobacterium tuberculosis (B) causes tuberculosis, not pneumonia. Escherichia coli (C) is associated with urinary tract infections and gastrointestinal infections, not pneumonia. Pseudomonas aeruginosa (D) is known to cause infections in immunocompromised individuals but is not a common cause of pneumonia.

A patient with diarrhea had fecal analysis revealing small, curved Gram-negative bacilli with a monotrichous flagellum. These bacteria do not form spores or capsules and thrive in alkaline conditions. What is the causative agent?

  • A. Vibrio cholerae
  • B. Escherichia coli
  • C. Salmonella
  • D. Shigella
Correct Answer: A

Rationale: Step 1: Small, curved Gram-negative bacilli with a monotrichous flagellum point towards a motile bacterium.
Step 2: The absence of spores or capsules and preference for alkaline conditions further narrows down the possibilities.
Step 3: Vibrio cholerae fits all criteria as it is a curved, motile, Gram-negative bacillus that thrives in alkaline environments.
Summary: Escherichia coli is a facultative anaerobe, Salmonella and Shigella are non-flagellated, and all of them can form capsules or spores, unlike Vibrio cholerae.

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