Microbiology Chapter 11 Test Bank

Microbiology Chapter 11 Test Bank Related

Review Microbiology Chapter 11 Test Bank related questions and content

During examination of a 3-month old infant a pediatrician revealed that the baby's oral mucosa and tongue were covered with a thick white deposit. In the material taken from the affected site a bacteriologist revealed the presence of yeast fungi giving the reasons for suspecting a fungal infection which occurs most often in children of this age, namely:

  • A. Candidiasis
  • B. Favus
  • C. Epidermophytosis
  • D. Actinomycosis
Correct Answer: A

Rationale: The correct answer is A: Candidiasis. In infants, a thick white deposit on the oral mucosa and tongue is indicative of oral thrush, which is caused by the yeast fungus Candida. Infants are particularly susceptible to Candidiasis due to their developing immune systems and use of antibiotics. Favus (B) is a chronic fungal infection of the scalp caused by Trichophyton schoenleinii, typically not seen in infants. Epidermophytosis (C) refers to superficial fungal infections of the skin caused by dermatophytes, not commonly found in the oral cavity of infants. Actinomycosis (D) is a bacterial infection caused by Actinomyces species, not a fungal infection.

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For shigella is true:

  • A. They produce hydrogen sulfide
  • B. They ferment lactose
  • C. They are nonmotile
  • D. All of them are mannitol positive
Correct Answer: C

Rationale: Step-by-step rationale:
1. Shigella is a nonmotile bacterium.
2. This lack of motility is a key characteristic used to differentiate it from other enteric bacteria.
3. Nonmotile nature of Shigella helps it to cause infections by invading the intestinal epithelial cells.
4. Therefore, choice C is correct as Shigella is indeed nonmotile.

Summary:
A: Incorrect - Shigella does not produce hydrogen sulfide.
B: Incorrect - Shigella does not ferment lactose.
D: Incorrect - Shigella is not mannitol positive.

The one-way transfer of genetic material from a donor cell to a recipient cell by direct cell-to-cell contact is:

  • A. transformation
  • B. transduction
  • C. replication
  • D. conjugation
Correct Answer: D

Rationale: Conjugation involves direct cell-to-cell contact for the transfer of genetic material, typically through a pilus. This process is well-documented in bacterial genetics. Transformation (A) involves uptake of free DNA from the environment. Transduction (B) is genetic transfer by a viral vector. Replication (C) is the process of producing identical copies of DNA or RNA. Therefore, the correct answer is D (conjugation) as it specifically refers to the one-way transfer of genetic material through direct cell-to-cell contact.

A wound infection culture revealed Gram-positive cocci in clusters. The bacteria were catalase-positive and coagulase-positive. What is the most likely causative agent?

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

Rationale: The correct answer is A: Staphylococcus aureus. This bacterium is characterized by Gram-positive cocci in clusters, catalase-positive, and coagulase-positive. Staphylococcus aureus is a common pathogen causing wound infections due to its ability to produce toxins and enzymes. Staphylococcus epidermidis (B) is catalase-positive but coagulase-negative, making it less likely to cause infections. Streptococcus pyogenes (C) is catalase-negative and typically causes streptococcal infections, not wound infections. Enterococcus faecalis (D) is catalase-negative and typically associated with urinary tract infections. Thus, Staphylococcus aureus is the most likely causative agent based on the given characteristics.

A patient's blood culture revealed Gram-positive rods capable of spore formation. They were also motile and produced gas in nutrient broth. What is the causative agent?

  • A. Clostridium perfringens
  • B. Bacillus anthracis
  • C. Clostridium tetani
  • D. Bacillus cereus
Correct Answer: A

Rationale: The correct answer is A: Clostridium perfringens. This bacterium fits all the characteristics mentioned: Gram-positive rods with spore formation, motile, and gas production in nutrient broth. Clostridium perfringens is known to cause gas gangrene, which aligns with the gas production in nutrient broth. Bacillus anthracis (B) causes anthrax and does not typically produce gas. Clostridium tetani (C) causes tetanus and does not form spores that are motile. Bacillus cereus (D) is a common cause of food poisoning and does not cause gas gangrene.

Which antibiotics against Parvovirus B19 can be found during the first 10-14 days of the infection:

  • A. IgG
  • B. IgA
  • C. IgD
  • D. IgM
Correct Answer: D

Rationale: The correct answer is D: IgM. IgM antibodies are the first type of antibodies produced by the immune system in response to an acute infection, such as Parvovirus B19. During the first 10-14 days of the infection, IgM antibodies are usually detectable in the blood, indicating a recent or ongoing infection. IgG antibodies (choice A) are produced later in the immune response and indicate past infection or immunity. IgA (choice B) is more commonly associated with mucosal immunity and may not be as prominent in the early stages of systemic infections. IgD (choice C) is primarily found on the surface of B cells and is involved in B cell activation but is not typically used as a marker for acute infections like IgM.

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