Nokea
Which of the following sites of the human body does not have a normal flora?
- A. Intestine
- B. Skin
- C. Vagina
- D. Blood
Correct Answer: D
Rationale: The correct answer is D: Blood. Normal flora refers to the microorganisms that naturally inhabit specific areas of the body. Blood is considered a sterile environment in healthy individuals, meaning it does not harbor any microorganisms under normal circumstances. In contrast, the intestine, skin, and vagina all have normal flora as they provide suitable environments for various microbial species to thrive. The presence of normal flora in these sites helps maintain a balance and protect against pathogenic invaders. Blood, being a vital and sterile fluid, is not meant to have any resident microbial populations.
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The tool of choice to observe living microorganisms is the
- A. bright-field microscope
- B. phase-contrast microscope
- C. fluorescence microscope
- D. electron microscope
Correct Answer: B
Rationale: The correct answer is B: phase-contrast microscope. This type of microscope is ideal for observing living microorganisms because it enhances the contrast of transparent specimens without the need for staining or fixing, allowing for clear visualization of internal structures and movements. Bright-field microscopes (A) are suitable for observing fixed and stained specimens, not living organisms. Fluorescence microscopes (C) are used to detect specific cellular components tagged with fluorescent markers, not ideal for observing overall morphology. Electron microscopes (D) use electron beams and are best for viewing detailed structures at high magnification, but are not suitable for observing living organisms due to the need for vacuum conditions.
Rocky Mountain spotted fever is caused by:
- A. Borrelia burgdorferi
- B. Rickettsia rickettsii
- C. Rickettsia prowazekii
- D. Ehrlichia chaffeensis
Correct Answer: B
Rationale: The correct answer is B: Rickettsia rickettsii. Rocky Mountain spotted fever is caused by Rickettsia rickettsii, a bacterium transmitted by ticks. This pathogen primarily affects the endothelial cells of blood vessels, leading to vasculitis. Borrelia burgdorferi (choice A) causes Lyme disease, not Rocky Mountain spotted fever. Rickettsia prowazekii (choice C) causes epidemic typhus, and Ehrlichia chaffeensis (choice D) causes human monocytic ehrlichiosis, both of which are distinct from Rocky Mountain spotted fever. Therefore, the correct choice is B based on the specific etiology of the disease.
Infection caused by the genus Candida can be successfully treated with:
- A. Penicillins
- B. Cephalosporins of third generation
- C. Nystatin
- D. None of the above
Correct Answer: C
Rationale: Step-by-step rationale for why choice C (Nystatin) is the correct answer:
1. Nystatin is an antifungal medication specifically effective against Candida infections.
2. Candida is a type of fungus, not a bacteria targeted by penicillins (choice A) or cephalosporins (choice B).
3. Nystatin works by disrupting the fungal cell membrane, leading to its death.
4. Choice D (None of the above) is incorrect as Nystatin is a suitable treatment option for Candida infections.
Which bacteria is known for causing the disease tetanus?
- A. Clostridium tetani
- B. Clostridium perfringens
- C. Neisseria gonorrhoeae
- D. Bacillus anthracis
Correct Answer: A
Rationale: Step-by-step rationale for why A is correct:
1. Clostridium tetani is known to produce tetanus toxin.
2. The tetanus toxin causes muscle rigidity and spasms characteristic of tetanus.
3. Clostridium perfringens is associated with gas gangrene, not tetanus.
4. Neisseria gonorrhoeae causes gonorrhea, not tetanus.
5. Bacillus anthracis causes anthrax, not tetanus.
In summary, Clostridium tetani is the correct answer as it is specifically associated with causing tetanus, while the other choices are associated with different diseases.
Which of the following is a host-dependent bacterium?
- A. Mycoplasma
- B. Ureaplasma
- C. Rickettsia
- D. Micrococcus
Correct Answer: C
Rationale: The correct answer is C: Rickettsia. Rickettsia is a host-dependent bacterium because it requires living cells of a host organism to survive and replicate. This bacterium is an obligate intracellular pathogen, meaning it cannot grow outside of a host cell.
A: Mycoplasma and B: Ureaplasma are not host-dependent as they can grow and reproduce in cell-free environments due to possessing their own unique cell wall structures.
D: Micrococcus is a free-living bacterium that can survive and reproduce independently without relying on a host organism.