Nokea
Examination of a smear from a chancre revealed mobile, long, spiral microorganisms with 8-12 regular coils. What is the causative agent?
- A. Treponema
- B. Leptospira
- C. Borrelia
- D. Vibrios
Correct Answer: A
Rationale: The correct answer is A: Treponema. The characteristics described match Treponema pallidum, the causative agent of syphilis. Treponema has long, spiral shape with 8-12 regular coils. Leptospira (B) is a spirochete but has fewer coils and causes leptospirosis. Borrelia (C) is another spirochete but typically has irregular coils and causes Lyme disease. Vibrios (D) are curved rods and not spirochetes.
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A patient was taken to a hospital with acute food poisoning caused by homemade canned mushrooms. The product analysis revealed some microorganisms that develop only in the absence of oxygen. What microorganisms caused the poisoning?
- A. Obligate anaerobes
- B. Facultative anaerobes
- C. Microaerophiles
- D. Obligate aerobes
Correct Answer: A
Rationale: The correct answer is A: Obligate anaerobes. These microorganisms thrive in the absence of oxygen, as seen in the canned mushrooms where oxygen is limited. They produce toxins causing food poisoning. Facultative anaerobes (B) can survive with or without oxygen. Microaerophiles (C) require low levels of oxygen. Obligate aerobes (D) need oxygen to survive and would not be responsible for the poisoning in this case.
When using gram staining method fungi stain:
- A. Blue-purple
- B. Red
- C. Silver
- D. Do not stain
Correct Answer: D
Rationale: The correct answer is D: Fungi do not stain in the gram staining method because they have a unique cell wall composition different from bacteria. Fungi have chitin in their cell walls, which is not easily stained by the gram staining process. This method primarily targets the peptidoglycan layer present in bacterial cell walls. Therefore, fungi will not take up the stain and will remain colorless. The other choices (A: Blue-purple, B: Red, C: Silver) are incorrect because they describe colors that are associated with staining results for bacteria, not fungi.
The phagocytosis is:
- A. Killing of bacterial cells with bactericidal antibiotics
- B. Blocking of key bacterial enzymes
- C. Active engulf and destruction of microorganisms by some host cells
- D. There is no correct answer
Correct Answer: C
Rationale: The correct answer is C because phagocytosis refers to the process where certain host cells engulf and destroy microorganisms. This is an essential mechanism of the immune system to eliminate pathogens. Choice A is incorrect because phagocytosis does not involve the use of antibiotics. Choice B is incorrect as it describes a different mechanism of action against bacteria. Choice D is incorrect because phagocytosis is a well-established biological process.
There are several cases of children from boarding school suffering from sore throat. Microscopy of tonsil smears stained according Neisser method has revealed thin yellow bacilli with dark brown grains on their ends placed in the shape of Roman numeral five. What infection can be suspected in this case?
- A. Diphtheria
- B. Scarlet fever
- C. Listeriosis
- D. Tonsilitis
Correct Answer: A
Rationale: Rationale for Correct Answer A (Diphtheria):
1. Thin yellow bacilli with dark brown grains on ends suggest Corynebacterium diphtheriae, characteristic of diphtheria.
2. Roman numeral five shape is typical of diphtheria bacilli.
3. Diphtheria causes sore throat and can spread in boarding schools.
4. Neisser staining method is used for diphtheria bacilli.
Summary of Incorrect Choices:
B: Scarlet fever is caused by Streptococcus pyogenes and presents with rash, not yellow bacilli.
C: Listeriosis is caused by Listeria monocytogenes, not consistent with the described findings.
D: Tonsillitis can be caused by various bacteria or viruses, but the specific characteristics described do not match.
A defined microorganism can be isolated in pure culture:
- A. From liquid and solid media
- B. From liquid nutrient media
- C. Only from single colonies on solid media
- D. None of the above
Correct Answer: C
Rationale: The correct answer is C because isolating a defined microorganism in pure culture involves obtaining a single, distinct colony on solid media. This ensures that only one type of microorganism is present in the culture, preventing contamination. Liquid media can harbor multiple organisms, making it challenging to isolate a specific microorganism. Therefore, choice A is incorrect. Choice B is also incorrect as liquid nutrient media does not provide the necessary isolation required for pure culture. Choice D is incorrect because isolating from single colonies on solid media allows for the pure culture of the defined microorganism.