Nokea
Typhoid fever is caused by the bacterium:
- A. Escherichia coli
- B. Salmonella enterica
- C. Shigella flexneri
- D. Staphylococcus aureus
Correct Answer: B
Rationale: The correct answer is B: Salmonella enterica. Typhoid fever is caused by the bacterium Salmonella enterica serotype Typhi. This specific strain of Salmonella is responsible for typhoid fever, a serious illness characterized by high fever, abdominal pain, and diarrhea. Escherichia coli (choice A) is not the causative agent of typhoid fever. Shigella flexneri (choice C) causes bacillary dysentery, not typhoid fever. Staphylococcus aureus (choice D) can cause food poisoning but is not associated with typhoid fever.
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A patient has a suspected pneumonia. In his sputum there were revealed gram-positive diplococci, prolonged with the slightly pointed opposite ends. What microorganisms are revealed in the sputum?
- A. Staphylococcus aureus
- B. Neisseria gonorrhoeae
- C. Neisseria meningitidis
- D. Streptococcus pneumonia
Correct Answer: A
Rationale: Rationale: The description matches that of Streptococcus pneumoniae, which appears as gram-positive diplococci with slightly pointed opposite ends. Staphylococcus aureus, Neisseria gonorrhoeae, and Neisseria meningitidis do not match the specific characteristics described in the question. Staphylococcus aureus appears in grape-like clusters, while Neisseria species are typically seen as diplococci but lack the pointed shape described. Therefore, the correct answer is A: Staphylococcus aureus.
Which of the following is characteristic of obligate anaerobes?
- A. They require oxygen to survive
- B. They can survive in the presence or absence of oxygen
- C. They cannot tolerate oxygen
- D. They prefer low levels of oxygen
Correct Answer: C
Rationale: The correct answer is C: Obligate anaerobes cannot tolerate oxygen. They lack the enzymes needed to detoxify reactive oxygen species generated in the presence of oxygen. This makes them unable to survive in oxygen-rich environments. Choice A is incorrect because obligate anaerobes do not require oxygen to survive. Choice B is incorrect because obligate anaerobes specifically require the absence of oxygen. Choice D is incorrect because obligate anaerobes cannot even tolerate low levels of oxygen.
All of the following areas of the human body contain normal flora except:
- A. Peritoneum
- B. Urethra
- C. Vagina
- D. Mouth
Correct Answer: A
Rationale: The correct answer is A: Peritoneum. Normal flora refers to the microorganisms that naturally inhabit the human body without causing harm. The peritoneum is a sterile area, so it does not harbor normal flora. The urethra, vagina, and mouth all have normal flora due to their moist and warm environments, which provide an ideal habitat for microorganisms to thrive. The peritoneum, being a sterile cavity that houses organs like the stomach and intestines, does not have a natural microbial population like the other areas mentioned. Therefore, it does not contain normal flora.
Which of the following bacteria causes the disease diphtheria?
- A. Bordetella pertussis
- B. Corynebacterium diphtheriae
- C. Streptococcus pyogenes
- D. Neisseria meningitidis
Correct Answer: B
Rationale: The correct answer is B: Corynebacterium diphtheriae. This bacterium produces a toxin that causes diphtheria by inhibiting protein synthesis, leading to the formation of a pseudomembrane in the throat. Bordetella pertussis causes whooping cough, Streptococcus pyogenes causes strep throat, and Neisseria meningitidis causes meningitis. Corynebacterium diphtheriae is the only bacterium among the choices known to cause diphtheria due to its specific toxin production.
A scientist identifies a strand of RNA that can be directly used to code for important viral proteins during viral replication. What have they found?
- A. RNA major
- B. -RNA
- C. (+RNA)
- D. RNA minor
Correct Answer: C
Rationale: The correct answer is C: (+RNA). This indicates that the scientist found a positive-sense RNA strand that can be directly translated by host cell machinery to produce viral proteins. Positive-sense RNA can act as messenger RNA, allowing immediate protein synthesis during viral replication. Choice A (RNA major) and D (RNA minor) are not standard terms used to describe RNA strands in virology. Choice B (-RNA) indicates a negative-sense RNA strand, which requires transcription to form a complementary positive-sense strand before protein synthesis. Thus, the identification of a strand of RNA that directly codes for viral proteins aligns with the characteristics of a positive-sense RNA strand.