Nokea
Which of the following antibodies is synthesized by the infant soon after birth?
- A. IgA
- B. IgM
- C. IgG
- D. IgD
Correct Answer: B
Rationale: The correct answer is B: IgM. IgM is the first antibody synthesized by the infant soon after birth. It is produced by B cells in response to initial exposure to antigens. IgA is mainly found in mucosal areas, IgG is transferred from mother to fetus, and IgD functions in the early stages of B cell development. Therefore, IgM is the most suitable choice as the antibody synthesized by the infant soon after birth.
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Pili are bacterial organelles for:
- A. Chemotaxis
- B. Adhesion
- C. Take part in the process of obtaining nutrients for bacteria
- D. None of the above
Correct Answer: B
Rationale: The correct answer is B: Adhesion. Pili are bacterial appendages that help bacteria adhere to surfaces. This is important for colonization and biofilm formation. Choice A (Chemotaxis) is incorrect because chemotaxis is the movement of bacteria in response to chemical stimuli, not the function of pili. Choice C (Nutrient acquisition) is incorrect because pili are not directly involved in obtaining nutrients. Choice D (None of the above) is incorrect as pili do serve a specific purpose, which is adhesion.
The cell envelope in gram positive bacteria is:
- A. Two-layer
- B. Three-layer
- C. One-layer
- D. There is no a cell envelope in gram-positive bacteria
Correct Answer: A
Rationale: The correct answer is A: Two-layer. In gram-positive bacteria, the cell envelope consists of two layers: the thick peptidoglycan layer and the cytoplasmic membrane. The peptidoglycan layer is much thicker compared to gram-negative bacteria, providing structural support and protection. The cytoplasmic membrane is located beneath the peptidoglycan layer and serves as a barrier between the cytoplasm and the external environment. The other choices are incorrect because gram-positive bacteria do have a cell envelope, it is composed of two layers, not three layers, and it is not just a single layer. Choice D is incorrect as it states that there is no cell envelope in gram-positive bacteria, which is not true.
Which of the following bacteria is responsible for causing the disease known as tuberculosis?
- A. Mycobacterium tuberculosis
- B. Neisseria meningitidis
- C. Salmonella enterica
- D. Streptococcus pneumoniae
Correct Answer: A
Rationale: The correct answer is A: Mycobacterium tuberculosis. This bacteria is responsible for causing tuberculosis because it is the specific pathogen known to infect the lungs and other parts of the body, leading to the disease. Mycobacterium tuberculosis has unique cell wall components that allow it to evade the immune system and survive in the host.
Neisseria meningitidis (B) causes meningitis, not tuberculosis. Salmonella enterica (C) causes food poisoning, not tuberculosis. Streptococcus pneumoniae (D) causes pneumonia, not tuberculosis. Therefore, the correct answer is A based on the specific characteristics and pathogenicity of Mycobacterium tuberculosis.
A 47-year-old male patient consulted a dentist about difficult mouth opening (lockjaw or trismus). The patient has a history of a stab wound of the lower extremity. What infection can be manifested by these symptoms?
- A. Tetanus
- B. Brucellosis
- C. Whooping cough
- D. Anaerobic wound infection
Correct Answer: A
Rationale: The correct answer is A: Tetanus. Tetanus is caused by the bacterium Clostridium tetani, commonly found in soil, dust, and animal feces. The patient's history of a stab wound increases the risk of tetanus infection as the bacterium can enter the body through the wound. Tetanus infection can lead to symptoms such as lockjaw or trismus, which are characterized by muscle stiffness and difficulty opening the mouth. This is due to the neurotoxin produced by Clostridium tetani affecting the muscles.
Summary of incorrect choices:
B: Brucellosis is a bacterial infection transmitted from animals to humans through consumption of unpasteurized dairy products. It does not typically manifest with symptoms of lockjaw.
C: Whooping cough (Pertussis) is a respiratory infection caused by Bordetella pertussis bacteria. It presents with severe coughing fits but does not cause lockjaw.
D: Anaerobic wound infection
A patient with acute food poisoning had fecal cultures grown on Endo agar, resulting in colorless colonies. What microorganism is most likely responsible?
- A. Salmonella
- B. Escherichia coli
- C. Staphylococcus
- D. Shigella
Correct Answer: A
Rationale: Step 1: Endo agar is a selective and differential media commonly used to isolate gram-negative bacteria.
Step 2: Colorless colonies on Endo agar indicate the absence of lactose fermentation.
Step 3: Salmonella is a gram-negative bacterium that does not ferment lactose, leading to colorless colonies on Endo agar.
Step 4: Therefore, the correct answer is A: Salmonella.
Summary:
B: Escherichia coli ferments lactose, producing pink colonies on Endo agar.
C: Staphylococcus is a gram-positive bacterium and would not grow on Endo agar.
D: Shigella is a gram-negative bacterium but ferments lactose, resulting in pink colonies on Endo agar.