Nokea
For enteropathogenic E. coli is true:
- A. They attach to enterocytes and destroy microvillus
- B. They are invasive and produce enterotoxin (no enterotoxin)
- C. Cause disease clinically similar to bacterial
- D. None of the above
Correct Answer: A
Rationale: Correct Answer: A
Rationale:
1. Enteropathogenic E. coli (EPEC) attach to enterocytes via a type III secretion system.
2. Once attached, they form attaching and effacing lesions on the microvilli, leading to microvillus destruction.
3. This mechanism allows EPEC to cause diarrhea by disrupting the normal absorptive function of the intestines.
Summary:
- B (They are invasive and produce enterotoxin) is incorrect because EPEC are non-invasive and do not produce enterotoxins.
- C (Cause disease clinically similar to bacterial) is vague and does not provide specific information about EPEC pathogenesis.
- D (None of the above) is incorrect as A is the correct explanation for EPEC pathogenicity.
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Which of the following statements for S. Aureus is FALSE
- A. it is always susceptible for penicillin
- B. around its colonies there is a beta hemolytic zone
- C. it produces hemolysins, leucocidins, enterotoxins
- D. has a positive catalase reaction
Correct Answer: A
Rationale: The correct answer is A because Staphylococcus aureus can develop resistance to penicillin over time due to the production of beta-lactamase enzymes. This resistance mechanism makes it no longer susceptible to penicillin. The other choices are correct: B) S. aureus can produce beta hemolysis, C) it produces various toxins like hemolysins, leucocidins, and enterotoxins, and D) it shows a positive catalase reaction due to the presence of catalase enzyme that converts hydrogen peroxide to water and oxygen.
A duodenal content smear of a patient with indigestion contains protozoa 10-18 mcm large. They have piriform bodies, 4 pairs of filaments, two symmetrically located nuclei in the broadened part of body. What kind of the lowest organisms is it?
- A. Lamblia
- B. Dysentery ameba
- C. Trichomonas
- D. Intestinal ameba
Correct Answer: A
Rationale: The correct answer is A: Lamblia. The description matches the characteristics of Giardia lamblia - a protozoan parasite that causes giardiasis. The piriform bodies, 4 pairs of filaments, and two symmetrically located nuclei are specific to Giardia lamblia. It is important to differentiate it from the other choices. Dysentery ameba (choice B) typically has a single nucleus and lacks the specific characteristics described. Trichomonas (choice C) is a flagellated protozoan with different morphology and does not match the given description. Intestinal ameba (choice D) such as Entamoeba histolytica usually has a single nucleus and different body shape compared to the described organism.
What is the role of bacterial ribosomes?
- A. Protein synthesis
- B. DNA replication
- C. Flagella formation
- D. Toxin production
Correct Answer: A
Rationale: The correct answer is A: Protein synthesis. Bacterial ribosomes are responsible for translating mRNA into proteins through a process called translation. This is a crucial step in gene expression, where amino acids are assembled into polypeptide chains. Choice B (DNA replication) is incorrect because ribosomes are not involved in DNA replication. Choice C (Flagella formation) is incorrect as ribosomes do not play a direct role in flagella formation. Choice D (Toxin production) is incorrect as ribosomes are not directly involved in producing toxins.
Production of RNA and DNA is called
- A. RNA splicing
- B. Translation
- C. Transposition
- D. Transcription
Correct Answer: D
Rationale: The correct answer is D: Transcription. This is the process where the DNA sequence is copied into an RNA molecule. It is the initial step in gene expression.
A: RNA splicing is the process of removing introns from pre-mRNA to create a mature mRNA molecule.
B: Translation is the process of synthesizing proteins using the information from mRNA.
C: Transposition is the movement of genetic elements within a genome.
In summary, transcription specifically refers to the synthesis of RNA from DNA, making it the correct choice compared to the other options.
Agglutination reaction is one of the following
- A. Ascoli ring test
- B. Western blot
- C. ELISA
- D. Reaction type Gruber
Correct Answer: A
Rationale: The correct answer is A: Ascoli ring test. Agglutination reaction in the Ascoli ring test is characterized by the formation of a visible ring at the interface of antigen and antibody. This reaction specifically tests for the presence of specific antibodies against antigens in serum, indicating a recent or current infection. The other options, Western blot, ELISA, and Reaction type Gruber, do not involve the agglutination reaction. Western blot and ELISA are immunoassay techniques that detect specific antibodies or antigens, while Reaction type Gruber is not a recognized method in immunology. Therefore, the Ascoli ring test is the correct choice for a test involving agglutination reaction.