ATI RN
medical microbiology test bank Questions
Question 1 of 5
A Gram-positive, spore-forming bacterium was isolated from a wound infection. The bacteria were anaerobic and produced gas. What is the most likely causative agent?
Correct Answer: A
Rationale: The correct answer is A: Clostridium perfringens. Clostridium perfringens is a Gram-positive, spore-forming bacterium that is anaerobic and produces gas. It is commonly associated with wound infections and gas gangrene. Clostridium tetani causes tetanus, not wound infections. Clostridium botulinum causes botulism, not typically associated with wound infections. Bacillus anthracis causes anthrax, which does not typically produce gas in wound infections.
Question 2 of 5
Which bacteria produce a toxin that causes botulism?
Correct Answer: B
Rationale: The correct answer is B: Clostridium botulinum. This bacterium produces the botulinum toxin, which causes botulism by blocking nerve functions. Clostridium tetani causes tetanus, not botulism. Staphylococcus aureus produces toxins that cause food poisoning, not botulism. Bacillus anthracis causes anthrax, not botulism.
Therefore, the correct choice is Clostridium botulinum because it is the specific bacterium responsible for producing the toxin that leads to botulism.
Question 3 of 5
In an urban settlement situated on the riverbank, an outbreak of hepatitis A was registered. The disease might have water origin. This assumption can be confirmed by growth of the following values of water quality:
Correct Answer: D
Rationale: The correct answer is D: Index of fecal coli-forms. Fecal coli-forms are bacteria found in the intestines of warm-blooded animals, including humans. Their presence in water indicates fecal contamination, which is a common source of hepatitis A transmission. Monitoring the index of fecal coli-forms can help identify potential sources of contamination and assess the risk of disease transmission.
A: Number of coli-phages - Coli-phages are viruses that infect coliform bacteria and are not directly related to fecal contamination.
B: Escherichia coli index - While E. coli is a type of coliform bacteria found in the intestines of warm-blooded animals, it alone may not be a reliable indicator of fecal contamination in water sources.
C: Oxidability - Oxidability is a measure of the water's ability to react with oxygen and does not provide direct information about fecal contamination or the presence of pathogens like hepatitis A.
In summary,
Question 4 of 5
Which one of the following microorganisms of genus Bacillus is associated with food intoxication:
Correct Answer: A
Rationale:
Rationale: Bacillus cereus is associated with food intoxication due to its ability to produce toxins that cause gastrointestinal symptoms. B. subtilis is not known to cause food intoxication. B. anthracis causes anthrax, not food intoxication. Option D is incorrect as not all Bacillus species cause food intoxication.
Question 5 of 5
On examination of a 6-year-old child the doctor noticed greyish film on the child's tonsils. Microscopy of the smear stained by Neisser method detected there Corynebacterium diphtheria. What morphologic feature was the most indicative for determining the type of the agent?
Correct Answer: C
Rationale: The correct answer is C: Polar placement of volutin granules. This feature is indicative of Corynebacterium diphtheria. Volutin granules are metachromatic granules found in the polar region of the bacterial cell, which is characteristic of this species. This feature helps differentiate it from other bacteria.
Explanation:
A: Fence-like position of the agent's cells is not a specific morphologic feature of Corynebacterium diphtheria.
B: Spores that exceed cells in diameter is not a characteristic feature of Corynebacterium diphtheria.
D: Presence of the capsule is not a distinguishing morphologic feature of Corynebacterium diphtheria.
In summary, the polar placement of volutin granules is the most indicative feature for determining the type of agent as Corynebacterium diphtheria, making it the correct choice.