Nokea
Which of the following bacteria can form spores that are resistant to extreme conditions?
- A. Staphylococcus aureus
- B. Bacillus subtilis
- C. Pseudomonas aeruginosa
- D. Neisseria gonorrhoeae
Correct Answer: B
Rationale: The correct answer is B: Bacillus subtilis. Bacillus subtilis is a Gram-positive bacterium known for forming endospores, which are resistant structures that allow the bacteria to survive harsh conditions like heat, radiation, and desiccation. This ability to form spores helps Bacillus subtilis to endure unfavorable environments. Staphylococcus aureus (A), Pseudomonas aeruginosa (C), and Neisseria gonorrhoeae (D) do not form spores and lack the same level of resistance to extreme conditions as Bacillus subtilis.
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A microscope that provides a three-dimensional image of a specimen is a
- A. dark-field microscope
- B. transmission electron microscope
- C. bright-field microscope
- D. scanning electron microscope
Correct Answer: D
Rationale: The correct answer is D: scanning electron microscope. A scanning electron microscope provides a three-dimensional image of a specimen by scanning a focused electron beam across the surface of the specimen, detecting the electrons that are emitted from the surface, and creating a detailed image. This is achieved through the detection of secondary electrons, backscattered electrons, and X-rays emitted from the specimen surface.
A dark-field microscope (choice A) utilizes oblique lighting to enhance contrast and is not specifically designed to provide a 3D image. A transmission electron microscope (choice B) uses a beam of electrons transmitted through a specimen to create a 2D image at high magnification. A bright-field microscope (choice C) is a basic microscope that illuminates a specimen with uniform light and does not provide a 3D image like a scanning electron microscope does.
Measures that can be taken to prevent bacterial vaginitis include:
- A. douching, use of contraceptive pills, and exercise
- B. use of absorbent tampons, frequent douching, and avoidance of tight pants
- C. avoidance of douching, use of panties with cotton crotch, and exercise
- D. avoidance of tight pants, use of panties with cotton crotch, and infrequent douching
Correct Answer: D
Rationale: The correct answer is D because bacterial vaginitis is often caused by an imbalance in the vaginal flora, which can be disrupted by frequent douching (eliminating beneficial bacteria), tight clothing (restricting airflow), and non-breathable underwear. Avoiding tight pants and using cotton underwear allow for better ventilation, promoting a healthy vaginal environment. Infrequent douching helps maintain the natural balance of bacteria in the vagina. Choices A and B are incorrect because they recommend practices that can disrupt the vaginal flora and increase the risk of bacterial vaginitis. Choice C is partially correct but lacks the emphasis on avoiding frequent douching, which is crucial in preventing bacterial vaginitis.
Microbial life on teeth was first observed by:
- A. Jenner
- B. Semmelweis
- C. Van Leeuwenhoek
- D. Pasteur
Correct Answer: C
Rationale: The correct answer is C: Van Leeuwenhoek. Van Leeuwenhoek was a Dutch scientist known for his pioneering work in microscopy. He was the first to observe microbial life, including bacteria on teeth, using his handmade microscopes in the 17th century. Jenner (choice A) is known for developing the smallpox vaccine, not for microbial observations. Semmelweis (choice B) discovered the importance of handwashing in preventing infections. Pasteur (choice D) is famous for his work on pasteurization and germ theory, but not specifically for observing microbial life on teeth. Van Leeuwenhoek's meticulous observations and groundbreaking discoveries make him the correct choice in this context.
During the incubation period S. Typhi multiplies in the
- A. small intestine enterocytes
- B. lumen of the small intestine
- C. hepatocytes
- D. macrophages of the Peyer patches and the solitary follicles
Correct Answer: D
Rationale: The correct answer is D because during the incubation period of Salmonella Typhi infection, the bacteria multiply in the macrophages of the Peyer's patches and solitary follicles. This is supported by the fact that S. Typhi is an intracellular pathogen that targets the lymphoid tissues of the intestines. Macrophages in these areas serve as the primary host cells for the bacteria, allowing for their replication and evasion of the host immune response. Choices A, B, and C are incorrect because S. Typhi does not primarily multiply in the small intestine enterocytes, the lumen of the small intestine, or hepatocytes during the initial stages of infection.
A puncture sample has been taken from the inguinal lymph nodes of a patient provisionally diagnosed with plague. The sample was inoculated into a hard nutrient medium. What shape will the colonies have, if the diagnosis is confirmed?
- A. Dewdrops
- B. Shagreen leather
- C. Lace handkerchief
- D. Mercury drops
Correct Answer: B
Rationale: The correct answer is B: Shagreen leather. Yersinia pestis, the bacterium causing plague, forms colonies resembling shagreen leather on a hard nutrient medium due to its distinctive morphology. This morphology includes a rough, irregular, and raised appearance, similar to the texture of shagreen leather.
A: Dewdrops - Incorrect. Dewdrops do not accurately describe the colony morphology of Yersinia pestis.
C: Lace handkerchief - Incorrect. Lace handkerchief does not accurately describe the colony morphology of Yersinia pestis.
D: Mercury drops - Incorrect. Mercury drops do not accurately describe the colony morphology of Yersinia pestis.