Nokea
Chlorhexidine:
- A. Is characterised by strong human toxicity
- B. Belongs to the group of alcohols and is widely used for disinfection of surfaces and sanitary facilities
- C. Belongs to the group of biguanides and is widely used for disinfection hands, skin and mucous membranes
- D. Is a disinfectant with limited application
Correct Answer: C
Rationale: Step 1: Chlorhexidine belongs to the group of biguanides, which are commonly used for disinfecting hands, skin, and mucous membranes.
Step 2: It is known to have broad-spectrum antimicrobial activity against various pathogens.
Step 3: The usage of chlorhexidine in healthcare settings for preoperative skin preparation and surgical hand scrub is well-established.
Step 4: The effectiveness and safety profile of chlorhexidine make it a preferred choice for disinfection purposes.
Summary:
- Option A is incorrect as chlorhexidine is not characterized by strong human toxicity.
- Option B is incorrect as chlorhexidine is not classified as an alcohol and is primarily used for disinfecting hands, skin, and mucous membranes.
- Option D is incorrect as chlorhexidine has a wide range of applications in disinfection, especially in healthcare settings.
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Conidiospores that bud off from a vase-shaped spore-bearing cell are referred to as:
- A. arthrospores
- B. porospores
- C. phialospores
- D. blastospores
Correct Answer: C
Rationale: The correct answer is C: phialospores. Phialospores are conidiospores that bud off from a vase-shaped spore-bearing cell called a phialide. This structure is characteristic of fungi in the genus Penicillium. Arthrospores (A) are formed by the fragmentation of hyphae, porospores (B) are not a recognized term in mycology, and blastospores (D) are produced by budding from yeast cells. Therefore, C is the correct choice based on the specific description provided in the question.
Humoral factors of the natural resistance are:
- A. Macrophages and macrophages
- B. Lysozyme, lactoferrin, interferon, complement
- C. B and T lymphocytes, NK cells
- D. Immunoglobulins A, G and M
Correct Answer: B
Rationale: The correct answer is B because lysozyme, lactoferrin, interferon, and complement are all humoral factors involved in natural resistance. Lysozyme and lactoferrin are antimicrobial proteins that help defend against pathogens. Interferon is a signaling protein that inhibits viral replication, while complement is a group of proteins that enhance the immune response by promoting inflammation and opsonization.
Choices A, C, and D are incorrect:
- Choice A mentions only macrophages, which are not humoral factors but rather phagocytic cells.
- Choice C lists immune cells involved in adaptive immunity (B and T lymphocytes, NK cells) rather than humoral factors of natural resistance.
- Choice D includes immunoglobulins, which are part of adaptive immunity, not natural resistance.
The main virulence factor of Neisseria meningitidis is?
- A. The polysaccharide capsule
- B. The beta lactamase
- C. The erythrogenic toxin
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A: The polysaccharide capsule. The capsule of Neisseria meningitidis plays a crucial role in its virulence by preventing phagocytosis, allowing the bacteria to evade the host's immune system. This leads to increased survival and colonization in the host.
Choice B: The beta lactamase is incorrect because it is an enzyme that breaks down beta-lactam antibiotics and does not directly contribute to the virulence of Neisseria meningitidis.
Choice C: The erythrogenic toxin is incorrect as this toxin is produced by Streptococcus pyogenes, not Neisseria meningitidis.
Choice D: None of the above is incorrect as the polysaccharide capsule is indeed a key virulence factor of Neisseria meningitidis.
Viruses can infect
- A. plants.
- B. bacteria.
- C. animals.
- D. all organisms.
Correct Answer: D
Rationale: The correct answer is D because viruses have the ability to infect all organisms, including plants, bacteria, animals, and even fungi. Viruses are non-living entities that require a host cell to replicate and spread. They can infect a wide range of organisms by attaching to specific receptors on the host cell's surface. Therefore, the correct answer is D as viruses have the capability to infect all living organisms. Choices A, B, and C are incorrect because viruses can infect not only plants, bacteria, and animals but also other organisms, making choice D the most comprehensive and accurate option.
A patient with bacterial endocarditis had Gram-positive cocci in chains isolated from blood cultures. The organism was catalase-negative. What is the most likely causative agent?
- A. Streptococcus pyogenes
- B. Staphylococcus aureus
- C. Enterococcus faecalis
- D. Micrococcus luteus
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pyogenes. This is because Streptococcus pyogenes is a Gram-positive cocci in chains bacterium that is catalase-negative, making it the most likely causative agent in this scenario. Streptococcus pyogenes is a common pathogen causing bacterial endocarditis.
Summary of other choices:
B: Staphylococcus aureus is a Gram-positive cocci bacterium but is catalase-positive, so it is unlikely in this case.
C: Enterococcus faecalis is a Gram-positive cocci bacterium, but it is catalase-negative, which is not consistent with the given information.
D: Micrococcus luteus is a Gram-positive cocci bacterium but is catalase-positive, making it an unlikely causative agent.