Nokea
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.
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Which of the following diseases is transmitted by the fecal–oral route?
- A. Ehrlichiosis
- B. Peptic ulcer
- C. Lyme disease
- D. Tularemia
Correct Answer: B
Rationale: The correct answer is B: Peptic ulcer. Peptic ulcers are commonly caused by Helicobacter pylori bacteria, which can be transmitted through the fecal-oral route. This means that the bacteria from infected feces can be ingested through contaminated food or water, leading to the development of peptic ulcers in the gastrointestinal tract.
Incorrect choices:
A: Ehrlichiosis - Ehrlichiosis is a tick-borne disease transmitted through the bite of an infected tick, not through the fecal-oral route.
C: Lyme disease - Lyme disease is also transmitted through the bite of an infected tick, specifically the black-legged tick.
D: Tularemia - Tularemia is a bacterial disease typically transmitted through insect bites, handling of infected animals, or ingestion of contaminated water, not through the fecal-oral route.
Warts are commonly caused by the:
- A. human papillomavirus
- B. herpesvirus
- C. HIV
- D. varicella-zoster virus
Correct Answer: A
Rationale: Step-by-step rationale:
1. Warts are caused by human papillomavirus (HPV) due to its ability to infect the skin.
2. HPV infects the top layer of skin and causes the rapid growth of cells, leading to the formation of warts.
3. Herpesvirus (choice B) causes herpes, not warts.
4. HIV (choice C) weakens the immune system but does not directly cause warts.
5. Varicella-zoster virus (choice D) causes chickenpox and shingles, not warts.
Summary:
Choice A is correct as warts are primarily caused by HPV, which infects the skin cells. Choices B, C, and D are incorrect as they are associated with different viral infections that do not lead to the development of warts.
Which bacterial structure helps in the movement towards or away from chemical stimuli?
- A. Flagella
- B. Pili
- C. Capsule
- D. Fimbriae
Correct Answer: A
Rationale: Flagella are the correct answer because they are long, whip-like structures that aid in bacterial movement towards or away from chemical stimuli. They rotate like propellers, allowing the bacterium to navigate its environment. Pili are used for attachment, not movement. Capsules are involved in protection and adherence, not chemotaxis. Fimbriae help in attachment to surfaces, not in movement towards stimuli.
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.
Tuberculosis can be treated by means of combined chemotherapy that includes substances with different mechanisms of action. What antituberculous medication inhibits transcription of RNA into DNA in mycobacteria?
- A. Rifampicin
- B. Isoniazid
- C. Streptomycin
- D. Ethionamide
Correct Answer: A
Rationale: Rifampicin is the correct answer because it inhibits RNA transcription in mycobacteria by binding to the bacterial RNA polymerase. This prevents the synthesis of RNA, leading to the inhibition of protein production essential for bacterial growth.
Isoniazid inhibits mycolic acid synthesis, Streptomycin inhibits protein synthesis, and Ethionamide disrupts mycolic acid synthesis. These mechanisms are different from inhibiting RNA transcription, making them incorrect choices.