microbiology basic and clinical principles test bank

microbiology basic and clinical principles test bank Related

Review microbiology basic and clinical principles test bank related questions and content

The infectious (non-sterile) immunity is:

  • A. cross-reactivity of antibodies
  • B. toxemia and formation of antitoxic antibodies
  • C. persistence of infectious agent
  • D. neutralization of infectious agent
Correct Answer: C

Rationale: The correct answer is C because infectious (non-sterile) immunity is achieved through the persistence of the infectious agent in the body, allowing the immune system to continuously recognize and combat the pathogen. This type of immunity provides long-lasting protection against future infections by the same agent.

Choice A (cross-reactivity of antibodies) is incorrect as it refers to the ability of antibodies to recognize similar antigens, not necessarily related to infectious immunity.

Choice B (toxemia and formation of antitoxic antibodies) is incorrect as it specifically relates to toxins produced by pathogens and the corresponding antibody response, not the persistence of the infectious agent itself.

Choice D (neutralization of infectious agent) is incorrect as it describes the process of antibodies binding to and inactivating pathogens, but it does not necessarily lead to long-term immunity through the persistence of the infectious agent.

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Complex communities of microorganisms on surfaces are called

  • A. colonies
  • B. biofilms
  • C. biospheres
  • D. flora
Correct Answer: B

Rationale: The correct answer is B: biofilms. Biofilms refer to complex communities of microorganisms that adhere to surfaces. They are characterized by a protective matrix that allows the microorganisms to communicate and cooperate. Colonies (A) typically refer to groups of a single species, not diverse communities. Biospheres (C) refer to the regions of the Earth where life exists, not specific microbial communities. Flora (D) generally refers to the plant life in a particular region, not microbial communities on surfaces.

For infections caused by coronaviruses is NOT true that;

  • A. Most commonly associated with URT infections
  • B. May be asymptomatic
  • C. SARS is an atypical pneumonia that can be complicated with acute respiratory failure and can cause death
  • D. Reinfections cannot be observed
Correct Answer: D

Rationale: Step-by-step rationale for why answer choice D is correct:
1. Coronaviruses can cause reinfections due to potential waning immunity.
2. Studies have shown cases of reinfections with different strains or within a short period.
3. This contradicts the notion that reinfections cannot be observed.
Summary:
A: Incorrect because some coronaviruses can cause lower respiratory tract infections.
B: Incorrect as coronaviruses can exhibit varied symptomatology including asymptomatic cases.
C: Incorrect as some coronaviruses like SARS can lead to severe pneumonia and complications.

Microscopy of sputum from a tuberculosis patient revealed acid-fast rods stained red using the Ziehl-Neelsen method. What structural feature allows this staining?

  • A. Mycolic acid in the cell wall
  • B. Capsule surrounding the cell
  • C. Flagella on the cell surface
  • D. Thick peptidoglycan layer
Correct Answer: A

Rationale: The correct answer is A: Mycolic acid in the cell wall. Mycolic acid is a unique component of the cell wall of Mycobacterium species, including the causative agent of tuberculosis. The Ziehl-Neelsen method uses acid-fast staining, where mycolic acid confers resistance to decolorization by acid-alcohol, causing the bacteria to retain the red stain. Choices B, C, and D are incorrect as capsules, flagella, and peptidoglycan layers do not directly contribute to acid-fast staining characteristic of Mycobacterium species.

It is often difficult for antibiotics to effectively reach the infection site of osteomyelitis primarily because of:

  • A. destruction of the local blood supply
  • B. denaturing of the drug by normal flora
  • C. inflammation and edema
  • D. excessive production of pus at the infection site
Correct Answer: A

Rationale: The correct answer is A: destruction of the local blood supply. In osteomyelitis, the infection occurs in the bone, which has a relatively poor blood supply compared to soft tissues. This limited blood flow makes it challenging for antibiotics to reach the infection site effectively, hindering their ability to combat the infection. Destruction of the local blood supply restricts the delivery of antibiotics and immune cells to the infected bone, leading to poor treatment outcomes.

Summary:
- Option A is correct because the limited blood supply in bones hinders antibiotic delivery.
- Option B is incorrect as denaturing by normal flora does not impact antibiotic reach to the infection site.
- Option C is incorrect as inflammation and edema, while present, do not primarily hinder antibiotic delivery.
- Option D is incorrect as excessive pus production does not directly impede antibiotic access to the infection site.

A fecal sample from a patient with diarrhea was cultured on Endo agar, resulting in colorless colonies. The bacteria were Gram-negative rods. What microorganism is most likely?

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

Rationale: The correct answer is B: Shigella. On Endo agar, Shigella appears as colorless colonies due to its inability to ferment lactose. Shigella is a Gram-negative rod and is a common cause of diarrhea. Salmonella (A) and Escherichia coli (C) would typically produce pink colonies on Endo agar as they can ferment lactose. Proteus (D) is not commonly associated with diarrhea and would not be expected to grow on Endo agar.

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