Microbiology A Systems Approach Test Bank

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A patient with convulsive contractions of facial muscles was admitted to the infectious disease ward. From a scratch on his lower right extremity analysts isolated bacteria with terminal endospores that gave them drumstick appearance. What bacteria are compliant with given description?

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

Rationale: Step-by-step rationale for the correct answer (A - Clostridium tetani):
1. The patient has convulsive contractions of facial muscles, indicating tetanus.
2. Isolation of bacteria with terminal endospores that have a drumstick appearance is characteristic of Clostridium tetani.
3. Clostridium tetani produces tetanospasmin toxin causing muscle spasms.
4. Therefore, the correct answer is Clostridium tetani (A).

Summary of why other choices are incorrect:
B: Clostridium botulinum causes botulism, not tetanus.
C: Clostridium perfringens causes gas gangrene, not tetanus.
D: Bacillus anthracis causes anthrax, not tetanus.

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Cholera is a serious gastrointestinal illness caused by bacteria of the genus:

  • A. Escherichia
  • B. Salmonella
  • C. Vibrio
  • D. Acinetobacter
Correct Answer: C

Rationale: The correct answer is C: Vibrio. Cholera is caused by Vibrio cholerae bacteria. These bacteria produce a toxin that causes severe diarrhea and dehydration. Escherichia (choice A) and Salmonella (choice B) are known for causing other types of gastrointestinal infections but not cholera. Acinetobacter (choice D) typically causes respiratory infections, not gastrointestinal illnesses like cholera. Therefore, the correct choice is Vibrio as it is specifically associated with cholera.

The effect of which of the following toxins DOES NOT MANIFEST with neurological symptoms:

  • A. Tetanospasmin
  • B. Diphtheria exotoxin
  • C. Botulinum exotoxin
  • D. Pertussis exotoxin
Correct Answer: D

Rationale: Certainly! The correct answer is D: Pertussis exotoxin. Pertussis toxin primarily affects the respiratory system causing whooping cough. It does not directly target the nervous system like the other toxins listed. Tetanospasmin causes muscle spasms, Diphtheria exotoxin affects the heart and nerves, and Botulinum exotoxin causes paralysis by blocking neurotransmitter release. Therefore, Pertussis exotoxin is the only toxin among the options that does not manifest with neurological symptoms.

Acute febrile pharyngitis and pharyngoconjunctival fever are often the clinical presentation of which viral infection:

  • A. VZV
  • B. Measles virus
  • C. Rubella virus
  • D. Adenovirus
Correct Answer: D

Rationale: The correct answer is D: Adenovirus. Adenovirus commonly causes acute febrile pharyngitis and pharyngoconjunctival fever. Adenovirus is known to cause respiratory infections and can present with symptoms such as sore throat, fever, and conjunctivitis. VZV (Varicella-Zoster Virus) causes chickenpox and shingles, not these specific symptoms. Measles virus causes a systemic illness with characteristic rash, not typically pharyngitis. Rubella virus causes a mild febrile illness with rash, but not pharyngitis. Therefore, based on the clinical presentation described, adenovirus is the most likely cause.

Which structure in bacteria allows them to exchange genetic material during conjugation?

  • A. Pili
  • B. Flagella
  • C. Capsule
  • D. Ribosomes
Correct Answer: A

Rationale: Pili in bacteria are responsible for conjugation, allowing the transfer of genetic material between cells. They form a bridge between donor and recipient cells, facilitating the exchange of DNA. Flagella are for movement, capsules for protection, and ribosomes for protein synthesis. Pili is the only structure directly involved in genetic material exchange.

A patient with severe abdominal pain and diarrhea had a stool sample cultured. The bacteria were Gram-negative rods that did not ferment lactose. What is the most likely causative agent?

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

Rationale: The correct answer is A: Salmonella enterica. This is because Salmonella are Gram-negative rods that do not ferment lactose, which fits the description in the question. Additionally, Salmonella is a common cause of severe abdominal pain and diarrhea. Shigella dysenteriae is a Gram-negative rod that also causes severe diarrhea but it does not share the characteristic of not fermenting lactose. Escherichia coli is a Gram-negative rod that does ferment lactose. Proteus vulgaris is also a Gram-negative rod but it is not commonly associated with severe abdominal pain and diarrhea, making it an unlikely causative agent in this scenario.

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