Nokea
The optochin sensitivity test demonstrates:
- A. Neisseria gonorrhoeae
- B. Pneumococcal
- C. Staphylococci
- D. Group A streptococci
Correct Answer: B
Rationale: The optochin sensitivity test is used to differentiate Pneumococcal (Streptococcus pneumoniae) from other streptococci. Optochin sensitivity is a characteristic feature of Pneumococcal, as it inhibits its growth. The test involves placing optochin discs on a culture plate and observing the zone of inhibition around the disc for Pneumococcal. Neisseria gonorrhoeae, Staphylococci, and Group A streptococci do not exhibit optochin sensitivity, making them incorrect choices. In summary, the optochin sensitivity test is specific to Pneumococcal, making choice B the correct answer.
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Which bacteria are capable of forming spores to survive in extreme conditions?
- A. Clostridium botulinum
- B. Bacillus anthracis
- C. Both A and B
- D. None of the above
Correct Answer: C
Rationale: The correct answer is C because both Clostridium botulinum and Bacillus anthracis are capable of forming spores to survive in extreme conditions. Clostridium botulinum is known for causing botulism and produces highly heat-resistant spores, while Bacillus anthracis is the causative agent of anthrax and also forms spores. Choice A is incorrect because only Clostridium botulinum is mentioned, not Bacillus anthracis. Choice B is incorrect because only Bacillus anthracis is mentioned, not Clostridium botulinum. Choice D is incorrect as it states that none of the bacteria can form spores, which is false based on the characteristics of Clostridium botulinum and Bacillus anthracis.
Bacteriological inspection of disinfection quality at a pharmacy revealed a microorganism in an utility room (in the sink). The microorganism has the following properties: mobile nonspore-forming gram- negative bacteria that form capsular substance, grow well on ordinary nutrient media, secrete the blue-green pigment. This microorganism is most likely to be of the following genus:
- A. Pseudomonas
- B. Proteus
- C. Clostridium
- D. Shigella
Correct Answer: A
Rationale: The correct answer is A: Pseudomonas.
Rationale:
1. Mobile nonspore-forming gram-negative bacteria with a capsule substance indicate Pseudomonas.
2. Pseudomonas grow well on ordinary nutrient media, matching the description.
3. The secretion of a blue-green pigment is a characteristic feature of Pseudomonas.
4. Proteus is a gram-negative bacterium but does not match all the given properties.
5. Clostridium is a gram-positive bacterium that forms spores.
6. Shigella is a gram-negative bacterium but does not have the other characteristics mentioned.
Therefore, based on the properties described, the most likely genus of the microorganism is Pseudomonas.
An example of selective media is:
- A. McConkey agar
- B. Bordet Gengou agar
- C. Peptone water
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A: McConkey agar. Selective media selectively inhibit the growth of certain organisms while allowing others to grow. McConkey agar contains crystal violet and bile salts that inhibit the growth of Gram-positive bacteria, making it selective for Gram-negative bacteria. Choices B and C are not selective media, as they do not specifically inhibit the growth of certain types of bacteria. Choice D is incorrect as McConkey agar is indeed an example of selective media.
Which bacteria are capable of forming spores to survive in harsh environments?
- A. Bacillus anthracis
- B. Clostridium botulinum
- C. Both A and B
- D. None of the above
Correct Answer: C
Rationale: The correct answer is C (Both A and B) because both Bacillus anthracis and Clostridium botulinum are capable of forming spores to survive in harsh environments. Bacillus anthracis causes anthrax and forms spores that can survive extreme conditions. Clostridium botulinum causes botulism and also forms spores for survival. Option A (Bacillus anthracis) and Option B (Clostridium botulinum) are incorrect on their own because they only represent one of the bacteria capable of forming spores. Option D (None of the above) is incorrect because it disregards the fact that both bacteria can form spores.
Which of the following is likely to be the most frequently used portal of entry for pathogens?
- A. Skin
- B. Gastrointestinal tract
- C. Respiratory tract
- D. Conjunctiva
Correct Answer: C
Rationale: The correct answer is C: Respiratory tract. The respiratory tract is likely the most frequently used portal of entry for pathogens because it is constantly exposed to the external environment and has a large surface area lined with mucous membranes that can trap and facilitate the entry of pathogens. Additionally, the respiratory tract serves as a direct pathway for pathogens to reach the bloodstream and other organs. Skin (choice A) is a physical barrier that can prevent pathogen entry, while the gastrointestinal tract (choice B) has acidic pH and enzymes that can kill many pathogens. Conjunctiva (choice D) is a less common portal of entry compared to the respiratory tract due to its smaller surface area and protective mechanisms such as tears.