Microbiology Chapter 14 Test Bank

Microbiology Chapter 14 Test Bank Related

Review Microbiology Chapter 14 Test Bank related questions and content

A 22-year-old patient is a clerk. His working day runs in a conditioned room. In summer he was taken by an acute disease with the following symptoms: fever, dyspnea, dry cough, pleural pain, myalgia, arthralgia. Objectively: moist rales on the right, pleural friction rub. X-ray picture showed infiltration of the inferior lobe. In blood: WBC - 11 · 109/l, stab neutrophils - 6%, segmented neutrophils - 70%, lymphocytes - 8%, ESR - 42 mm/h. What is the etiological factor pneumonia?

  • A. Legionella
  • B. Mycoplasma
  • C. Streptococcus
  • D. Staphylococcus
Correct Answer: C

Rationale: The correct answer is C: Streptococcus. Streptococcus pneumoniae is the most common etiological factor for community-acquired pneumonia in young adults. The symptoms described align with typical pneumococcal pneumonia presentation. Presence of pleural friction rub and infiltration in the X-ray support the diagnosis. The blood work showing elevated WBC count with a left shift (increased neutrophils and low lymphocytes) and elevated ESR is consistent with a bacterial infection. Legionella and Mycoplasma typically present with atypical pneumonia symptoms such as headache, confusion, and GI symptoms, which are not described in the case. Staphylococcus pneumonia is not a common cause of community-acquired pneumonia in young adults.

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Nonchromosomal DNA molecules found in a bacterial cell are

  • A. endospores.
  • B. transposons.
  • C. plasmids.
  • D. prions.
Correct Answer: C

Rationale: The correct answer is C: plasmids. Plasmids are nonchromosomal DNA molecules commonly found in bacterial cells, providing additional genetic material for bacteria. They are not essential for bacterial survival but can confer advantages such as antibiotic resistance. Endospores (A) are dormant bacterial structures resistant to harsh conditions. Transposons (B) are mobile genetic elements that can move within a genome. Prions (D) are misfolded proteins causing neurodegenerative diseases, not DNA molecules.

Which organism is responsible for cholera?

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

Rationale: The correct answer is B: Vibrio cholerae. Cholera is caused by this specific bacterium. Vibrio cholerae produces a toxin that leads to severe diarrhea and dehydration. Salmonella typhi causes typhoid fever, Escherichia coli can cause various infections but not cholera, and Shigella dysenteriae causes dysentery, not cholera. Therefore, the correct choice is B.

A patient with a sore throat had a throat smear revealing Gram-positive cocci in pairs. The bacteria were catalase-negative and beta-hemolytic. What is the most likely causative agent?

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

Rationale: The correct answer is A: Streptococcus pyogenes.
Rationale:
1. Gram-positive cocci in pairs suggest Streptococcus species.
2. Catalase-negative rules out Staphylococcus.
3. Beta-hemolytic indicates Streptococcus pyogenes due to its beta-hemolytic properties.
Summary:
B: Streptococcus pneumoniae is catalase-negative but not beta-hemolytic.
C: Enterococcus faecalis is not typically beta-hemolytic.
D: Staphylococcus aureus is catalase-positive and not typically in pairs.

A 23-year old medical student arrives in the student health clinic complaining of difficult in swallowing, sore throat, and chills. Upon examination, she is found to be running a fever and has white patches on her tonsils. A throat swab is positive for streptococcus pyogenes (group A). A diagnosis of acute pharyngitis is made. Her past medical history is unremarkable except an anaphylactic reaction to cefaclor two years ago. Which of the following would be a safe alternative for treating?

  • A. Amoxicillin
  • B. Meropenem
  • C. Cephalexin
  • D. Clindamycin
Correct Answer: D

Rationale: The correct answer is D: Clindamycin. Clindamycin is a lincosamide antibiotic that is safe to use in patients with a history of anaphylaxis to beta-lactam antibiotics like cefaclor. Clindamycin is effective against streptococcus pyogenes and is a suitable alternative in this case. Amoxicillin (choice A) is a beta-lactam antibiotic similar to cefaclor and may cause a cross-reactive allergic reaction. Meropenem (choice B) is a carbapenem antibiotic and not typically used for acute pharyngitis. Cephalexin (choice C) is a cephalosporin antibiotic and may also cause cross-reactivity in patients with a history of anaphylaxis to cefaclor.

Which bacteria is responsible for causing the disease known as whooping cough?

  • A. Clostridium botulinum
  • B. Bordetella pertussis
  • C. Streptococcus pneumoniae
  • D. Neisseria meningitidis
Correct Answer: B

Rationale: The correct answer is B: Bordetella pertussis. This bacterium causes whooping cough by infecting the respiratory tract. It produces toxins that lead to severe coughing fits characteristic of the disease. Clostridium botulinum (A) causes botulism, Streptococcus pneumoniae (C) causes pneumonia, and Neisseria meningitidis (D) causes meningitis, not whooping cough. B. pertussis is the only bacterium specifically associated with whooping cough.

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