Nokea
Which bacterium is known for producing an exotoxin that causes severe diarrhea?
- A. Clostridium tetani
- B. Clostridium botulinum
- C. Vibrio cholerae
- D. Shigella dysenteriae
Correct Answer: C
Rationale: Rationale:
1. Vibrio cholerae produces cholera toxin causing severe diarrhea.
2. Clostridium tetani causes tetanus, not diarrhea.
3. Clostridium botulinum causes botulism, not diarrhea.
4. Shigella dysenteriae causes dysentery, not typical diarrhea.
Summary:
A: Incorrect, causes tetanus.
B: Incorrect, causes botulism.
C: Correct, produces cholera toxin causing severe diarrhea.
D: Incorrect, causes dysentery.
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Examination of the duodenal contents revealed some pear-shaped protozoa with two nuclei and four pairs of flagella. The organisms had also two axostyles between the nuclei and a ventral adhesive disc. What protozoan representative was found in the patient?
- A. Lamblia
- B. Toxoplasma
- C. Leishmania
- D. Intestinal trichomonad
Correct Answer: A
Rationale: Step 1: Pear-shaped protozoa with two nuclei, four pairs of flagella, two axostyles, and a ventral adhesive disc match the characteristics of Giardia lamblia.
Step 2: Giardia lamblia is commonly found in the duodenum and causes giardiasis.
Step 3: Lamblia is the correct answer as it specifically matches all the described characteristics.
Summary: B, Toxoplasma, is incorrect as it does not match the described features. C, Leishmania, does not have the specific characteristics mentioned. D, Intestinal trichomonad, does not match the detailed descriptions given.
For measles virus is true that:
- A. There is no outer membrane
- B. Contains singles-stranded RNA with negative polarity
- C. Belongs to family Togaviridae
- D. Cannot be grown on cell cultures
Correct Answer: B
Rationale: The correct answer is B: Contains single-stranded RNA with negative polarity. Measles virus is an enveloped virus with a single-stranded RNA genome that is negative-sense. This means it must first be transcribed into positive-sense RNA before it can be translated. Choice A is incorrect as the measles virus does have an outer envelope. Choice C is incorrect as measles virus belongs to the family Paramyxoviridae, not Togaviridae. Choice D is incorrect as measles virus can be grown on cell cultures, specifically on Vero cells.
Mycoplasma species lack:
- A. Cell wall
- B. Plasma membrane
- C. DNA
- D. Ribosomes
Correct Answer: A
Rationale: The correct answer is A: Cell wall. Mycoplasma species lack a cell wall, making them unique among bacteria. This is because they have a flexible cell membrane that provides structural support instead of a rigid cell wall. The absence of a cell wall allows them to be pleomorphic and gives them resistance to certain antibiotics targeting cell wall synthesis. Plasma membrane (B), DNA (C), and ribosomes (D) are present in Mycoplasma species, so they are not the correct answer.
Which microbial group can resist acidic pH?
- A. yeast and molds
- B. bacteria
- C. E. Coli
- D. none of the above
Correct Answer: A
Rationale: The correct answer is A: yeast and molds. Yeast and molds can resist acidic pH due to their ability to maintain a stable internal pH through various mechanisms such as ion transport and cell wall composition. Bacteria, including E. coli, are generally more sensitive to acidic conditions. Choice D is incorrect as yeast and molds are known to thrive in acidic environments.
Which of the following statements is not correct with regard to Mycobacterium tuberculosis and/or the disease it caused?
- A. The pathogen contains mycolic acid in the cell wall
- B. The pathogen can live intracellularly in macrophages
- C. The antibodies formed are protective
- D. None of the above
Correct Answer: C
Rationale: Rationale:
C is the correct answer because antibodies formed against Mycobacterium tuberculosis are not protective. They do not efficiently clear the infection due to the bacterium's ability to evade the immune response by residing intracellularly in macrophages. Antibodies play a minimal role in controlling tuberculosis compared to cell-mediated immunity.
Summary:
A is incorrect because Mycobacterium tuberculosis does contain mycolic acid in its cell wall. B is incorrect because the pathogen can indeed live intracellularly in macrophages. D is incorrect as C is the correct answer.