Nokea
Protein A is located in the cell wall of:
- A. Coagulase negative staphylococcus
- B. Staphylococcus aureus
- C. Micrococcus
- D. None of them
Correct Answer: B
Rationale: Protein A is a virulence factor specific to Staphylococcus aureus. This protein binds to the Fc region of immunoglobulins, inhibiting opsonization and phagocytosis. Therefore, the correct answer is B. Coagulase negative staphylococcus (choice A) does not produce Protein A. Micrococcus (choice C) is a different genus and does not possess Protein A. Choice D is incorrect because Protein A is indeed found in Staphylococcus aureus.
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What is a common characteristic of spore-forming bacteria?
- A. Resistance to heat and dehydration
- B. Ability to produce toxins
- C. Presence of flagella
- D. Ability to photosynthesize
Correct Answer: A
Rationale: The correct answer is A: Resistance to heat and dehydration. Spore-forming bacteria form spores as a survival mechanism in harsh conditions. These spores are highly resistant to heat and dehydration, allowing the bacteria to withstand extreme environments. This characteristic is essential for their long-term survival and ability to persist in unfavorable conditions. Choices B, C, and D are incorrect because not all spore-forming bacteria produce toxins, have flagella, or are capable of photosynthesis. These characteristics are not exclusive to spore-forming bacteria and do not define them as a group.
A patient had been provisionally diagnosed with syphilis. A laboratory assistant took the blood serum for an immunologic test based on the detection of antibodies preventing the movement of treponemas and causing their death. What reaction was used for the diagnosis?
- A. Immobilization
- B. Complement binding
- C. Agglutination
- D. Precipitation
Correct Answer: A
Rationale: The correct answer is A: Immobilization. This technique is called the Treponema pallidum immobilization (TPI) test, used to diagnose syphilis. The rationale is as follows:
1. TPI test detects antibodies that prevent the movement of treponemas, causing their death.
2. By immobilizing the treponemas, it indicates the presence of specific antibodies against syphilis.
3. This test is highly specific for syphilis diagnosis as it directly targets the causative agent.
Other choices are incorrect:
B: Complement binding - Not specific to syphilis, more commonly used for other diseases.
C: Agglutination - Detects clumping of particles, not specific to treponemas or syphilis.
D: Precipitation - Involves the formation of a solid, not directly related to treponema movement or death.
A wound culture revealed Gram-positive cocci in clusters. The bacteria were catalase-positive and coagulase-negative. What is the most likely microorganism?
- A. Staphylococcus epidermidis
- B. Staphylococcus aureus
- C. Streptococcus pyogenes
- D. Enterococcus faecalis
Correct Answer: A
Rationale: The correct answer is A: Staphylococcus epidermidis. The presence of Gram-positive cocci in clusters indicates a staphylococcal species. The fact that the bacteria are catalase-positive and coagulase-negative further narrow it down to Staphylococcus epidermidis, as this species fits all the given characteristics.
- Choice B, Staphylococcus aureus, is coagulase-positive.
- Choice C, Streptococcus pyogenes, is a streptococcal species, not staphylococcal.
- Choice D, Enterococcus faecalis, is a Gram-positive cocci but is catalase-negative and not typically found in clusters.
The optimal PH for most pathogenic bacteria and viruses is:
- A. 5.0-5.5
- B. 8.0-9.6
- C. 7.2-7.4
- D. 4.2-4.4
Correct Answer: C
Rationale: The correct answer is C (7.2-7.4) because most pathogenic bacteria and viruses thrive in a neutral pH environment close to 7.0. This pH range is optimal for their growth and survival. Choice A (5.0-5.5) is too acidic for most pathogens. Choice B (8.0-9.6) is too alkaline, which is not conducive for their survival. Choice D (4.2-4.4) is also too acidic and would likely inhibit the growth of pathogenic bacteria and viruses. Thus, a pH range of 7.2-7.4 provides the most suitable conditions for their proliferation.
Pili are bacterial organelles for:
- A. Chemotaxis
- B. Adhesion
- C. Take part in the process of obtaining nutrients for bacteria
- D. None of the above
Correct Answer: B
Rationale: The correct answer is B: Adhesion. Pili are bacterial appendages that help bacteria adhere to surfaces. This is important for colonization and biofilm formation. Choice A (Chemotaxis) is incorrect because chemotaxis is the movement of bacteria in response to chemical stimuli, not the function of pili. Choice C (Nutrient acquisition) is incorrect because pili are not directly involved in obtaining nutrients. Choice D (None of the above) is incorrect as pili do serve a specific purpose, which is adhesion.