Nokea
Which of the following bacteria is known to cause strep throat?
- A. Streptococcus pyogenes
- B. Staphylococcus aureus
- C. Neisseria gonorrhoeae
- D. Clostridium tetani
Correct Answer: A
Rationale: Step 1: Streptococcus pyogenes is commonly known as Group A Streptococcus, which is the primary bacteria responsible for causing strep throat.
Step 2: Staphylococcus aureus is not typically associated with strep throat but can cause skin infections and other illnesses.
Step 3: Neisseria gonorrhoeae is the bacteria responsible for gonorrhea, a sexually transmitted infection, not strep throat.
Step 4: Clostridium tetani causes tetanus, a bacterial infection that affects the nervous system and is not related to strep throat.
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Which bacterial structure allows for attachment to host cells?
- A. Flagella
- B. Fimbriae
- C. Capsule
- D. Endospore
Correct Answer: B
Rationale: The correct answer is B: Fimbriae. Fimbriae are hair-like appendages found on the surface of bacteria that enable attachment to host cells. This attachment is crucial for establishing infection. Flagella (A) are used for movement, not attachment. Capsules (C) provide protection and help evade the host immune system, but do not directly facilitate attachment. Endospores (D) are dormant structures for survival, not for attachment to host cells. Fimbriae specifically aid in adherence to host cells, making them the correct choice in this context.
Which bacteria is responsible for causing tuberculosis?
- A. Mycobacterium tuberculosis
- B. Streptococcus pneumoniae
- C. Salmonella enterica
- D. Neisseria meningitidis
Correct Answer: A
Rationale: The correct answer is A: Mycobacterium tuberculosis. This bacterium is responsible for causing tuberculosis. It is a slow-growing, acid-fast bacillus that primarily affects the lungs. Mycobacterium tuberculosis is transmitted through the air via respiratory droplets. Choice B, Streptococcus pneumoniae, is a common cause of pneumonia but not tuberculosis. Choice C, Salmonella enterica, causes food poisoning. Choice D, Neisseria meningitidis, causes meningitis, not tuberculosis. Therefore, Mycobacterium tuberculosis is the correct answer based on its characteristics and mode of transmission.
The Gram stain is used to differentiate bacteria based on:
- A. Cell shape
- B. Cell wall structure
- C. Flagella composition
- D. Nutrient requirements
Correct Answer: B
Rationale: The Gram stain differentiates bacteria based on cell wall structure. It classifies bacteria into Gram-positive (purple) and Gram-negative (pink) based on the presence of peptidoglycan in the cell wall. This method helps in identifying the bacterial species and determining appropriate treatment. Option A (Cell shape) is incorrect because the Gram stain focuses on cell wall composition, not cell shape. Option C (Flagella composition) is incorrect as the Gram stain does not assess flagella. Option D (Nutrient requirements) is incorrect as it does not relate to the purpose of the Gram stain.
Which of the following bacteria are unable to synthesize ATP?
- A. Chlamydia
- B. Enterococci
- C. Rickettsia
- D. Staphylococci
Correct Answer: A
Rationale: The correct answer is A: Chlamydia. Chlamydia lacks the essential enzymes for ATP synthesis and relies on host cell ATP. Enterococci, Rickettsia, and Staphylococci possess the necessary enzymes for ATP synthesis through cellular respiration. Chlamydia's inability to synthesize ATP makes it dependent on the host cell for energy production, distinguishing it from the other bacteria listed.
Tuberculosis can be treated by means of combined chemotherapy that includes substances with different mechanisms of action. What antituberculous medication inhibits transcription of RNA into DNA in mycobacteria?
- A. Rifampicin
- B. Isoniazid
- C. Streptomycin
- D. Ethionamide
Correct Answer: A
Rationale: Rifampicin is the correct answer because it inhibits RNA transcription in mycobacteria by binding to the bacterial RNA polymerase. This prevents the synthesis of RNA, leading to the inhibition of protein production essential for bacterial growth.
Isoniazid inhibits mycolic acid synthesis, Streptomycin inhibits protein synthesis, and Ethionamide disrupts mycolic acid synthesis. These mechanisms are different from inhibiting RNA transcription, making them incorrect choices.