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Which bacteria are capable of forming endospores?
- A. Staphylococcus aureus
- B. Clostridium tetani
- C. Neisseria gonorrhoeae
- D. Escherichia coli
Correct Answer: B
Rationale: The correct answer is B: Clostridium tetani. Endospores are formed by certain bacteria as a survival mechanism in harsh conditions. Clostridium species, including C. tetani, have the ability to form endospores. Staphylococcus aureus (A), Neisseria gonorrhoeae (C), and Escherichia coli (D) do not produce endospores. Staphylococcus aureus is a gram-positive cocci bacterium, Neisseria gonorrhoeae is a gram-negative diplococci bacterium, and Escherichia coli is a gram-negative rod-shaped bacterium. Therefore, the correct choice is Clostridium tetani as it is known for its ability to form endospores.
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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.
Which bacteria are capable of producing exotoxins?
- A. Clostridium tetani
- B. Staphylococcus aureus
- C. Escherichia coli
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D: All of the above. Clostridium tetani, Staphylococcus aureus, and Escherichia coli are all capable of producing exotoxins. Exotoxins are proteins released by bacteria that can cause damage to the host. Clostridium tetani produces tetanospasmin, causing tetanus. Staphylococcus aureus produces toxins like enterotoxin and toxic shock syndrome toxin-1. Escherichia coli can produce Shiga toxin and heat-labile toxin. Therefore, all three bacteria listed can produce exotoxins, making choice D the correct answer. Choices A, B, and C are incorrect as they do not encompass all the bacteria capable of producing exotoxins.
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.
In 8 days after a surgery the patient developed tetanus. The surgeon suspects this condition to be caused by suture material contaminated by tetanus agent. The material is delivered to a bacteriological laboratory. What nutrient medium is required for primary inoculation of the suture material?
- A. Kitt-Tarozzi medium.
- B. Endo agar.
- C. Sabouraud agar.
- D. Egg-yolk salt agar.
Correct Answer: A
Rationale: The correct answer is A: Kitt-Tarozzi medium. This medium is used for the primary inoculation of suture material suspected of causing tetanus. The rationale is that Kitt-Tarozzi medium contains the necessary nutrients to support the growth of Clostridium tetani, the bacterium responsible for tetanus. This medium is selective and helps in isolating the specific pathogen from the contaminated suture material.
Summary of other choices:
B: Endo agar is used for the isolation of Gram-negative bacteria from clinical and non-clinical samples.
C: Sabouraud agar is used for the isolation of fungi and yeast.
D: Egg-yolk salt agar is used for the detection of lipase-producing bacteria, particularly Staphylococcus aureus.
A patient with fever, enlarged lymph nodes, and bacteremia was diagnosed with plague. The Gram-stained smear revealed bipolar-staining, Gram-negative rods. What is the causative agent?
- A. Yersinia pestis
- B. Francisella tularensis
- C. Brucella abortus
- D. Clostridium botulinum
Correct Answer: A
Rationale: The correct answer is A: Yersinia pestis. Y. pestis is the causative agent of plague, characterized by fever, enlarged lymph nodes, and bacteremia. The bipolar-staining, Gram-negative rods seen on Gram stain are typical of Y. pestis.
Incorrect choices:
B: Francisella tularensis causes tularemia, not plague.
C: Brucella abortus causes brucellosis, not plague.
D: Clostridium botulinum causes botulism, not plague.
In summary, the key features of the patient's presentation and the Gram stain findings align with Yersinia pestis as the correct causative agent of plague.