Nokea
Which bacteria is responsible for causing the disease known as whooping cough?
- A. Clostridium botulinum
- B. Bordetella pertussis
- C. Streptococcus pneumoniae
- D. Neisseria meningitidis
Correct Answer: B
Rationale: The correct answer is B: Bordetella pertussis. This bacterium causes whooping cough by infecting the respiratory tract. It produces toxins that lead to severe coughing fits characteristic of the disease. Clostridium botulinum (A) causes botulism, Streptococcus pneumoniae (C) causes pneumonia, and Neisseria meningitidis (D) causes meningitis, not whooping cough. B. pertussis is the only bacterium specifically associated with whooping cough.
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The development of polioviruses on cell cultures is characterized by:
- A. Cytopathic effect
- B. Cytotoxic effect
- C. Cytolytic effect
- D. They Don't Change The Cell Cultures
Correct Answer: A
Rationale: The correct answer is A: Cytopathic effect. This is because polioviruses cause visible changes in infected cells, leading to cell damage and death, known as cytopathic effect. This is a key characteristic of viral infection. Choice B (Cytotoxic effect) is incorrect as it refers to the toxicity of a substance to cells, not the specific effect of polioviruses. Choice C (Cytolytic effect) is incorrect as it specifically refers to cell lysis, which is not the primary mechanism of poliovirus infection. Choice D (They Don't Change The Cell Cultures) is incorrect because polioviruses do indeed cause changes in cell cultures due to their cytopathic effect.
A bacteriological laboratory tests canned meat for botulinum toxin. Extract of the tested material and ABE botulinum antitoxin serum was introduced into the test group of mice; a control group of mice received the extract without antibotulinic serum. What serological reaction was used?
- A. Neutralization
- B. Precipitation
- C. Complement binding
- D. Double immunodiffusion
Correct Answer: A
Rationale: The correct answer is A: Neutralization. In this experiment, the ABE botulinum antitoxin serum is introduced along with the extract to neutralize the botulinum toxin. This is a specific type of serological reaction where the antitoxin serum binds to and neutralizes the toxin, preventing it from causing harm.
Summary:
- B: Precipitation involves the formation of visible insoluble complexes, which is not the case in this experiment.
- C: Complement binding involves the activation of complement proteins, which is not the main mechanism at play here.
- D: Double immunodiffusion is a technique to detect the presence of specific antigens or antibodies, but it is not directly related to the neutralization of toxins as seen in this experiment.
In the micropreparation made from patient's regional lymph node punctate and stained according to Romanovsky-Giemsa method, the doctor found out thin microorganisms with 12-14 equal ringlets and pale- pink sharp pointes 10-13 mkm in length. The pathogen of what disease is it about?
- A. Leishmaniasis
- B. Leptospirosis
- C. Surra
- D. Relapsing fever
Correct Answer: D
Rationale: The thin microorganisms described with 12-14 equal ringlets and pale-pink sharp points are characteristic of Borrelia spirochetes, the causative agent of relapsing fever. The ringlet appearance corresponds to the characteristic coiled structure of Borrelia spirochetes. The length of 10-13 mkm falls within the typical size range of Borrelia spirochetes. This pathogen is commonly identified in Romanovsky-Giemsa stained samples from patients with relapsing fever.
Summary of other choices:
A: Leishmaniasis - Leishmania parasites are larger and do not have the described ringlets or pale-pink sharp points.
B: Leptospirosis - Leptospira bacteria are not described as having ringlets or pale-pink sharp points.
C: Surra - Surra is caused by Trypanosoma evansi, and the description does not match the characteristics of this parasite.
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.
What is a viral capsid?
- A. protein envelope around the nucleic acid
- B. protein-coated nucleic acid
- C. the outer membrane of all viruses
- D. lipoprotein membrane
Correct Answer: B
Rationale: The correct answer is B because a viral capsid is a protein coat that surrounds and protects the viral nucleic acid (DNA or RNA). It helps in the attachment of the virus to host cells and protects the genetic material during transmission. Choice A is incorrect because a viral capsid is composed of proteins, not an envelope. Choice C is incorrect because not all viruses have an outer membrane. Choice D is incorrect because a viral capsid is primarily made up of proteins, not lipids.