Nokea
Bacteria causing bacillary dysentery can be isolated from the patient's blood:
- A. There is no bacteremia
- B. During the second week of illness
- C. During the first week of illness
- D. None of the above
Correct Answer: A
Rationale: Rationale:
1. Bacillary dysentery primarily affects the intestinal tract, not the bloodstream.
2. Bacteremia is rare in bacillary dysentery, as the infection is localized.
3. Isolating bacteria from the blood is not a typical diagnostic feature.
4. Therefore, the correct answer is A.
Summary:
Bacteria causing bacillary dysentery are not typically isolated from the patient's blood due to the localized nature of the infection. Choices B and C are incorrect as they suggest specific timeframes, which are not relevant to bacteremia in this context. Choice D is incorrect as bacteremia is not associated with bacillary dysentery.
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Which of the following bacteria is known to cause strep throat?
- A. Streptococcus pyogenes
- B. Staphylococcus aureus
- C. Neisseria gonorrhoeae
- D. Clostridium tetani
Correct Answer: A
Rationale: Step 1: Streptococcus pyogenes is commonly known as Group A Streptococcus, which is the primary bacteria responsible for causing strep throat.
Step 2: Staphylococcus aureus is not typically associated with strep throat but can cause skin infections and other illnesses.
Step 3: Neisseria gonorrhoeae is the bacteria responsible for gonorrhea, a sexually transmitted infection, not strep throat.
Step 4: Clostridium tetani causes tetanus, a bacterial infection that affects the nervous system and is not related to strep throat.
Which bacteria produces an enterotoxin that causes diarrhea?
- A. Vibrio cholerae
- B. Clostridium botulinum
- C. Escherichia coli
- D. Streptococcus pneumoniae
Correct Answer: A
Rationale: The correct answer is A: Vibrio cholerae. This bacterium produces the cholera toxin, an enterotoxin that causes profuse watery diarrhea by disrupting the normal function of the intestines. Vibrio cholerae is specifically known for causing cholera, a severe diarrheal disease. Clostridium botulinum (B) produces botulinum toxin, causing botulism (paralysis, not diarrhea). Escherichia coli (C) can produce enterotoxins, but the question specifies a specific enterotoxin causing diarrhea, which is not a characteristic of all strains of E. coli. Streptococcus pneumoniae (D) is a common cause of respiratory infections but does not produce an enterotoxin causing diarrhea.
The major function of bacterial flagella is:
- A. Attachment to surfaces
- B. Movement of the bacterial cell
- C. Protein synthesis
- D. Nutrient absorption
Correct Answer: B
Rationale: The correct answer is B: Movement of the bacterial cell. Bacterial flagella are whip-like appendages that enable bacteria to move towards nutrients or away from harmful substances. This movement is essential for survival, dispersal, and colonization. Choice A is incorrect because attachment is primarily mediated by other structures like pili. Choice C is incorrect as protein synthesis occurs inside the cell and is not directly related to flagella. Choice D is incorrect as nutrient absorption is typically carried out through specific channels or transport systems, not by flagella.
While examining the feces of a patient with diarrhea, cysts with four nuclei were found. What protozoan is most likely causing the condition?
- A. Entamoeba histolytica
- B. Lamblia
- C. Trichomonas
- D. Balantidium
Correct Answer: A
Rationale: The correct answer is A: Entamoeba histolytica. This protozoan causes amoebiasis, which presents with symptoms like diarrhea. The cysts with four nuclei found in the feces are characteristic of Entamoeba histolytica. This protozoan is known to cause invasive infection, leading to tissue destruction and ulcers in the intestines. Lamblia (choice B) typically presents with cysts containing two nuclei. Trichomonas (choice C) is a sexually transmitted parasite and does not form cysts. Balantidium (choice D) is a ciliated protozoan that does not have four nuclei in its cyst form.
Which of the following is characteristic of obligate anaerobes?
- A. They require oxygen to survive
- B. They can survive in the presence or absence of oxygen
- C. They cannot tolerate oxygen
- D. They prefer low levels of oxygen
Correct Answer: C
Rationale: The correct answer is C: Obligate anaerobes cannot tolerate oxygen. They lack the enzymes needed to detoxify reactive oxygen species generated in the presence of oxygen. This makes them unable to survive in oxygen-rich environments. Choice A is incorrect because obligate anaerobes do not require oxygen to survive. Choice B is incorrect because obligate anaerobes specifically require the absence of oxygen. Choice D is incorrect because obligate anaerobes cannot even tolerate low levels of oxygen.