Nokea
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.
You may also like to solve these questions
The bacteria that causes whooping cough is:
- A. Bordetella pertussis
- B. Haemophilus influenzae
- C. Pseudomonas aeruginosa
- D. Streptococcus pneumoniae
Correct Answer: A
Rationale: The correct answer is A: Bordetella pertussis. Whooping cough is caused by this bacteria, which specifically infects the respiratory tract. Bordetella pertussis produces toxins that lead to the characteristic symptoms of the disease. Haemophilus influenzae, Pseudomonas aeruginosa, and Streptococcus pneumoniae are not the causative agents of whooping cough. Haemophilus influenzae can cause respiratory infections, Pseudomonas aeruginosa is associated with hospital-acquired infections, and Streptococcus pneumoniae is a common cause of pneumonia and other respiratory infections, but none of these bacteria are responsible for whooping cough.
A patient underwent esophagogastroduodenoscopy. Analysis of the biopsy material enabled doctors to diagnose him with helicobacteriosis. What property of the bacteria found in this patient had to be obligatory taken into account during their cultivation?
- A. Microaerophilic ability
- B. Presence of urease
- C. Absence of spores and capsules
- D. Colonisation of gastral cells
Correct Answer: A
Rationale: Step-by-step rationale for why choice A is correct:
1. Helicobacter pylori, the bacteria causing helicobacteriosis, is microaerophilic, requiring low oxygen levels.
2. Cultivation conditions must mimic the natural environment of the bacteria.
3. Failure to provide a microaerophilic environment can hinder bacterial growth.
4. Thus, the ability to cultivate these bacteria requires consideration of their microaerophilic nature.
Summary:
- Choice A is correct because Helicobacter pylori is a microaerophilic bacteria.
- Choice B (Presence of urease) is incorrect as it is a characteristic used for diagnosis, not cultivation.
- Choice C (Absence of spores and capsules) is incorrect as it does not relate to cultivation requirements.
- Choice D (Colonization of gastral cells) is incorrect as it pertains to bacterial behavior, not cultivation needs.
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 child cut his leg with a piece of glass while playing and was brought to the clinic for the injection of tetanus toxoid. In order to prevent the development of anaphylactic shock the serum was administered by Bezredka method. What mechanism underlies this method of desensitization of the body?
- A. Binding of IgE fixed to the mast cells
- B. Blocking the mediator synthesis in the mast cells
- C. Stimulation of immune tolerance to the antigen
- D. Stimulation of the synthesis of antigenspecific IgG
Correct Answer: A
Rationale: The correct answer is A: Binding of IgE fixed to the mast cells. The Bezredka method involves injecting small, gradually increasing doses of the antigen (tetanus toxoid) to desensitize the body and prevent anaphylactic shock. This process works by binding the IgE antibodies fixed to mast cells, thereby reducing the release of allergic mediators like histamine. This prevents the cascade of events that lead to anaphylactic shock.
Choice B (Blocking the mediator synthesis in the mast cells) is incorrect because the Bezredka method does not block mediator synthesis but rather prevents the release of mediators by binding IgE.
Choice C (Stimulation of immune tolerance to the antigen) is incorrect as the Bezredka method does not primarily focus on inducing immune tolerance but rather on preventing anaphylactic reactions.
Choice D (Stimulation of the synthesis of antigen-specific IgG) is incorrect because the Bezredka method targets IgE antibodies on mast cells
Which of the following diseases is generally caused by contaminated food?
- A. Mumps
- B. Shigellosis
- C. Legionellosis
- D. Tuberculosis
Correct Answer: B
Rationale: The correct answer is B: Shigellosis. Shigellosis is caused by the bacteria Shigella, commonly transmitted through contaminated food and water. The bacteria can spread easily in unsanitary conditions. Mumps (A) is a viral infection spread through respiratory droplets. Legionellosis (C) is caused by the Legionella bacteria found in water sources like cooling towers. Tuberculosis (D) is a bacterial infection transmitted through the air. Therefore, the correct answer is B as it directly relates to contaminated food transmission.