The establishment and further spreading of an infectious disease within a new population is a process called:
- A. emergence
- B. adoption
- C. inclusion
- D. appearance
Correct Answer: A
Rationale: The correct answer is A: emergence. The term emergence refers to the process of a new infectious disease appearing and spreading within a population. It signifies the initial introduction and establishment of the disease in the new population.
Explanation for other choices:
B: Adoption does not accurately describe the process of a disease spreading within a new population.
C: Inclusion is not a term commonly used to describe the spread of infectious diseases.
D: Appearance is too vague and does not capture the complexity of the process of establishment and spreading of an infectious disease.
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The cytoplasmic membrane of the eukaryotes, in contrast to the one of prokaryotes, has:
- A. cellulose
- B. starch
- C. chitin
- D. sterols
Correct Answer: D
Rationale: The correct answer is D: sterols. Eukaryotic cytoplasmic membranes contain sterols, such as cholesterol, which provide stability and regulate fluidity. This is a key characteristic that distinguishes them from prokaryotic membranes. Cellulose (A) is a component of plant cell walls, not the cytoplasmic membrane. Starch (B) is a carbohydrate used for energy storage in plants. Chitin (C) is a component of fungal cell walls and arthropod exoskeletons, not found in eukaryotic cytoplasmic membranes.
A blood culture from a patient with sepsis revealed Gram-positive cocci in clusters. The bacteria were catalase-positive and coagulase-negative. What is the most likely causative agent?
- A. Staphylococcus epidermidis
- B. Staphylococcus aureus
- C. Streptococcus pyogenes
- D. Enterococcus faecalis
Correct Answer: A
Rationale: The correct answer is A: Staphylococcus epidermidis. This is supported by the characteristics of Gram-positive cocci in clusters, catalase-positive, and coagulase-negative. Staphylococcus epidermidis fits all these criteria, as it is a common skin commensal that can cause infections in immunocompromised individuals. Staphylococcus aureus (choice B) is catalase-positive and coagulase-positive. Streptococcus pyogenes (choice C) is catalase-negative. Enterococcus faecalis (choice D) is catalase-negative and not typically seen in clusters. Therefore, based on the given information, Staphylococcus epidermidis is the most likely causative agent.
A patient with a sore throat and fever had a throat culture revealing Gram-positive cocci in chains. The bacteria were 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 bacterium fits the description of Gram-positive cocci in chains and is catalase-negative. S. pyogenes commonly causes sore throat (pharyngitis) and fever, making it the most likely causative agent in this scenario. Staphylococcus aureus (B) is catalase-positive and is not typically associated with pharyngitis. Enterococcus faecalis (C) is not typically found in chains and is rarely a cause of acute pharyngitis. Micrococcus luteus (D) is not typically associated with pharyngitis and is catalase-positive.
Infection caused by the genus Candida can be successfully treated with:
- A. Penicillins
- B. Cephalosporins of third generation
- C. Nystatin
- D. None of the above
Correct Answer: C
Rationale: Step-by-step rationale for why choice C (Nystatin) is the correct answer:
1. Nystatin is an antifungal medication specifically effective against Candida infections.
2. Candida is a type of fungus, not a bacteria targeted by penicillins (choice A) or cephalosporins (choice B).
3. Nystatin works by disrupting the fungal cell membrane, leading to its death.
4. Choice D (None of the above) is incorrect as Nystatin is a suitable treatment option for Candida infections.
Cytoplasmic membrane of the prokaryotes consists of:
- A. Phospholipids
- B. Proteins
- C. Carbohydrates
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D: All of the above. The cytoplasmic membrane of prokaryotes consists of phospholipids which form a lipid bilayer, providing structure and selective permeability. Proteins are embedded in this membrane, serving various functions like transport and signaling. Carbohydrates may also be present on the surface for cell recognition. Therefore, all three components (phospholipids, proteins, and carbohydrates) are essential parts of the prokaryotic cytoplasmic membrane. Option A, B, and C individually do not fully encapsulate the complexity and composition of the prokaryotic cytoplasmic membrane.