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Which of the following bacteria produce exotoxins that cause severe gastrointestinal illness?
- A. Clostridium botulinum
- B. Vibrio cholerae
- C. Escherichia coli
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D (All of the above) because all three bacteria listed produce exotoxins that cause severe gastrointestinal illness. Clostridium botulinum produces botulinum toxin causing botulism. Vibrio cholerae produces cholera toxin leading to cholera. Escherichia coli can produce various exotoxins causing different types of severe gastrointestinal illnesses like E. coli O157:H7 causing bloody diarrhea. Therefore, all choices A, B, and C are correct in this case as they all produce exotoxins causing severe gastrointestinal illness.
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Microscopy of sputum from a tuberculosis patient revealed acid-fast rods stained red using the Ziehl-Neelsen method. What structural feature allows this staining?
- A. Mycolic acid in the cell wall
- B. Capsule surrounding the cell
- C. Flagella on the cell surface
- D. Thick peptidoglycan layer
Correct Answer: A
Rationale: The correct answer is A: Mycolic acid in the cell wall. Mycolic acid is a unique component of the cell wall of Mycobacterium species, including the causative agent of tuberculosis. The Ziehl-Neelsen method uses acid-fast staining, where mycolic acid confers resistance to decolorization by acid-alcohol, causing the bacteria to retain the red stain. Choices B, C, and D are incorrect as capsules, flagella, and peptidoglycan layers do not directly contribute to acid-fast staining characteristic of Mycobacterium species.
Which type of bacteria are capable of surviving in high salt concentrations?
- A. Acidophiles
- B. Thermophiles
- C. Halophiles
- D. Mesophiles
Correct Answer: C
Rationale: Correct Answer: C: Halophiles
Rationale:
1. Halophiles are bacteria adapted to high salt environments.
2. They have specific mechanisms to tolerate high salt concentrations.
3. Acidophiles thrive in acidic conditions.
4. Thermophiles prefer high temperature environments.
5. Mesophiles grow best at moderate temperatures.
A 30-year-old patient complains about having abdominal pain and diarrhea for five days; body temperature rise up to 37, 5oC along with chills. The day before a patient had been in a forest and drunk from an open water reservoir. Laboratory analyses enabled to make the following diagnosis: amebic dysentery. What is the drug of choice for its treatment?
- A. Metronidazole
- B. Furazolidonum
- C. Levomycetin
- D. Phthalazol
Correct Answer: A
Rationale: The correct answer is A: Metronidazole.
Rationale:
1. Metronidazole is the drug of choice for amebic dysentery due to its effectiveness against the causative agent, Entamoeba histolytica.
2. Metronidazole has good tissue penetration and is able to reach the site of infection in the gut.
3. It is a bactericidal drug that acts by disrupting the DNA structure of the parasite.
4. Metronidazole is well-absorbed orally and has minimal side effects.
Summary of other choices:
B: Furazolidonum - Not the drug of choice for amebic dysentery. It is primarily used for treating bacterial diarrhea.
C: Levomycetin - Not effective against Entamoeba histolytica and not recommended for amebic dysentery.
D: Phthalazol - Not commonly used for amebic dysentery treatment. Metronidazole is preferred due
Complex communities of microorganisms on surfaces are called
- A. colonies
- B. biofilms
- C. biospheres
- D. flora
Correct Answer: B
Rationale: The correct answer is B: biofilms. Biofilms refer to complex communities of microorganisms that adhere to surfaces. They are characterized by a protective matrix that allows the microorganisms to communicate and cooperate. Colonies (A) typically refer to groups of a single species, not diverse communities. Biospheres (C) refer to the regions of the Earth where life exists, not specific microbial communities. Flora (D) generally refers to the plant life in a particular region, not microbial communities on surfaces.
According to the location of flagella on their surface, bacteria can be:
- A. Monotrichous
- B. Amphitrichous
- C. Peritrichous
- D. All of these
Correct Answer: D
Rationale: The correct answer is D, "All of these." Monotrichous bacteria have a single flagellum at one end, amphitrichous have flagella at both ends, and peritrichous have flagella distributed all over the surface. The answer D is correct because it includes all these possibilities based on flagella location. Monotrichous is incorrect as it only refers to a single flagellum, amphitrichous is incorrect as it only refers to flagella at both ends, and peritrichous is incorrect as it only refers to flagella all over the surface. Therefore, the correct answer encompasses all these options.