microbiology basic and clinical principles test bank

microbiology basic and clinical principles test bank Related

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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.

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A large-scale reaction with parapertussis and pertussis diagnosticums was made in order to make serological diagnostics of the whooping cough. At the bottom of the test-tubes with diagnosticum of Bordetella parapertussis a granular sediment formed. What antibodies did this reaction reveal?

  • A. Agglutinins
  • B. Precipitins
  • C. Opsonins
  • D. Bacteriolysins
Correct Answer: B

Rationale: The correct answer is B: Precipitins. When a granular sediment forms at the bottom of the test-tubes, it indicates the formation of antigen-antibody complexes that are insoluble and precipitate out of the solution. Precipitins are antibodies that specifically react with antigens to form insoluble complexes. Agglutinins cause clumping of cells, opsonins enhance phagocytosis, and bacteriolysins lyse bacteria. These processes do not result in the formation of a granular sediment, making them incorrect choices in this context.

Which of the following bacteria is responsible for causing cholera?

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

Rationale: The correct answer is B: Vibrio cholerae. Cholera is caused by Vibrio cholerae, a bacterium that infects the small intestine, leading to severe diarrhea and dehydration. This bacterium produces a toxin that causes the symptoms of cholera.
A: Shigella dysenteriae causes dysentery, not cholera.
C: Salmonella enterica causes food poisoning, not cholera.
D: Escherichia coli can cause food poisoning but not cholera.

A fecal sample cultured on Endo agar revealed colorless colonies. The bacteria were Gram-negative rods and lactose non-fermenters. What microorganism is most likely?

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

Rationale: The correct answer is Shigella (Choice C) because it matches the description of being Gram-negative rods and lactose non-fermenters. Shigella is a non-lactose fermenting, Gram-negative rod that typically produces colorless colonies on Endo agar. Salmonella (Choice A) and Escherichia coli (Choice B) are both lactose fermenters and would produce pink colonies on Endo agar. Proteus (Choice D) is also a lactose fermenter and would appear pink on Endo agar. Therefore, based on the characteristics provided, Shigella is the most likely microorganism in this scenario.

For tuberculosis prevention the newborns got an injection of a vaccine. What vaccine was used?

  • A. BCG
  • B. Mantoux
  • C. DTaP vaccine
  • D. Anatoxin
Correct Answer: A

Rationale: The correct answer is A: BCG. BCG vaccine is commonly used for tuberculosis prevention because it provides immunity against Mycobacterium tuberculosis. Mantoux is a test, not a vaccine. DTaP vaccine is for diphtheria, tetanus, and pertussis, not tuberculosis. Anatoxin is a type of toxoid vaccine, not used for tuberculosis prevention. BCG vaccine has been shown to be effective in preventing severe forms of tuberculosis in infants, making it the appropriate choice in this scenario.

Which of the following bacteria is known for causing the disease tetanus?

  • A. Clostridium tetani
  • B. Clostridium perfringens
  • C. Streptococcus pyogenes
  • D. Escherichia coli
Correct Answer: A

Rationale: The correct answer is A: Clostridium tetani. This bacterium is known for causing tetanus due to its ability to produce tetanospasmin, a neurotoxin that leads to the characteristic muscle stiffness and spasms seen in tetanus. Clostridium perfringens (Choice B) is associated with gas gangrene, Streptococcus pyogenes (Choice C) causes streptococcal infections, and Escherichia coli (Choice D) is known for causing various gastrointestinal infections. Therefore, Choices B, C, and D are incorrect as they are not the causative agents of tetanus.

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