Nokea
The pertussis toxin:
- A. Changes the protein synthesis
- B. Provokes overproduction of mucus in the tracheal cells
- C. Changes the adenylate cyclase-mediated conversion of ATP to cyclic AMP
- D. Provokes release of electrolytes
Correct Answer: C
Rationale: The pertussis toxin inhibits the adenylate cyclase-mediated conversion of ATP to cyclic AMP, leading to decreased levels of cyclic AMP in the cell. This disrupts important cellular signaling pathways, affecting immune response and causing symptoms of pertussis. Choices A, B, and D are incorrect because the pertussis toxin does not directly affect protein synthesis, provoke overproduction of mucus in tracheal cells, or provoke release of electrolytes.
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Which bacteria are responsible for causing the disease known as leprosy?
- A. Mycobacterium leprae
- B. Escherichia coli
- C. Clostridium botulinum
- D. Staphylococcus aureus
Correct Answer: A
Rationale: The correct answer is A: Mycobacterium leprae. This bacterium is responsible for causing leprosy because it has a unique ability to infect the skin, nerves, and mucous membranes. It is an acid-fast bacillus that multiplies very slowly, leading to a chronic infection. Clostridium botulinum (choice C) causes botulism, Escherichia coli (choice B) causes various gastrointestinal infections, and Staphylococcus aureus (choice D) causes skin infections and other diseases, but none of these bacteria are associated with leprosy.
A smear from a sore throat revealed rod-shaped bacteria with polar granules. What is the most likely causative agent?
- A. Corynebacterium diphtheriae
- B. Streptococcus pneumoniae
- C. Haemophilus influenzae
- D. Klebsiella pneumoniae
Correct Answer: A
Rationale: The most likely causative agent is Corynebacterium diphtheriae. Step 1: Presence of rod-shaped bacteria indicates a bacillus. Step 2: Polar granules suggest metachromatic granules seen in C. diphtheriae. Step 3: C. diphtheriae causes diphtheria, which presents with sore throat. Summary: B is incorrect as S. pneumoniae is a cocci, not a bacillus. C is incorrect as H. influenzae is a pleomorphic coccobacillus. D is incorrect as K. pneumoniae is a large, encapsulated bacillus.
Which of the following characteristics of mumps infection is NOT true:
- A. Only the person can be infected
- B. Is a vaccine-preventable disease
- C. Is a highly contagious disease
- D. Transmission routes are via air droplets and direct contact
Correct Answer: A
Rationale: Step-by-step rationale:
1. Mumps is a contagious disease transmitted through air droplets and direct contact.
2. The correct answer is A because mumps can infect both humans and animals.
3. Choice B is incorrect as mumps is vaccine-preventable.
4. Choice C is correct as mumps is highly contagious.
5. Choice D is accurate as mumps is transmitted via air droplets and direct contact.
Summary:
The correct answer is A because mumps can infect both humans and animals, making it untrue that only humans can be infected. Choices B, C, and D are incorrect as mumps is vaccine-preventable, highly contagious, and transmitted through air droplets and direct contact.
Choose which one fo the following microorganisms is an example of obligate parasitism
- A. HIV
- B. E. Coli
- C. S. Epidermidis
- D. Pseudomonas aeruginosa
Correct Answer: A
Rationale: The correct answer is A: HIV. HIV is an example of obligate parasitism because it requires a host cell to replicate and survive. It cannot live independently outside of a host organism. In contrast, choices B, C, and D are not obligate parasites. E. Coli and S. Epidermidis are examples of commensal bacteria that can live in the host without causing harm. Pseudomonas aeruginosa can be both an opportunistic pathogen and a free-living organism, not strictly dependent on a host for survival.
Researchers of a bacteriological laboratory examine tinned meat for botulinic toxin. For this purpose a group of mice was injected with an extract of the material under examination and antitoxic antibotulinic serum of A, B, E types. A control group of mice was injected with the same extract but without antibotulinic serum. What serological reaction was applied?
- A. Neutralization
- B. Precipitation
- C. Complement binding
- D. Double immune diffusion
Correct Answer: A
Rationale: The correct answer is A: Neutralization. In this experiment, the researchers used antitoxic antibotulinic serum of different types to neutralize the botulinic toxin in tinned meat extract injected into mice. Neutralization is the process of rendering a toxin harmless by combining it with specific antibodies. The purpose of injecting the antitoxic serum was to neutralize the toxin and prevent it from causing harm to the mice. This serological reaction of neutralization directly aligns with the objective of the experiment.
Summary of other choices:
B: Precipitation - Precipitation involves the formation of a visible insoluble complex when an antigen reacts with its corresponding antibody. This process was not described in the scenario.
C: Complement binding - Complement binding involves the activation of the complement system by antigen-antibody complexes. This was not the main focus of the experiment described.
D: Double immune diffusion - This technique is used to detect the presence of specific antigens or antibodies