Nokea
What type of bacteria is responsible for causing tuberculosis?
- A. Mycobacterium tuberculosis
- B. Escherichia coli
- C. Clostridium botulinum
- D. Salmonella enterica
Correct Answer: A
Rationale: The correct answer is A: Mycobacterium tuberculosis. This bacterium is responsible for causing tuberculosis, as it has unique characteristics that allow it to infect the lungs and evade the immune system, leading to a chronic infection. Mycobacterium tuberculosis is a slow-growing, acid-fast bacterium that can survive and replicate within macrophages, causing the characteristic granulomas seen in tuberculosis.
Choice B, Escherichia coli, is a common gut bacterium and is not responsible for tuberculosis. Choice C, Clostridium botulinum, causes botulism, not tuberculosis. Choice D, Salmonella enterica, causes food poisoning, not tuberculosis.
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The role of pili in bacteria is:
- A. protection from desiccation
- B. motility
- C. adhesion to surfaces and conjugation
- D. spore formation
Correct Answer: C
Rationale: The correct answer is C: adhesion to surfaces and conjugation. Pili are hair-like structures on the surface of bacteria that help them adhere to surfaces and facilitate the transfer of genetic material during conjugation. This is essential for bacterial survival and reproduction. Choice A is incorrect because protection from desiccation is typically associated with other structures like capsules. Choice B is incorrect as motility in bacteria is usually facilitated by flagella. Choice D is incorrect as spore formation involves the formation of specialized structures, not pili.
Which of the following is a characteristic feature of Gram-positive bacteria?
- A. Outer membrane
- B. Thin peptidoglycan layer
- C. Thick peptidoglycan layer
- D. Presence of LPS
Correct Answer: C
Rationale: The correct answer is C: Thick peptidoglycan layer. Gram-positive bacteria have a thick peptidoglycan layer in their cell wall, which retains the crystal violet stain during Gram staining. This thick layer is a key characteristic feature that helps differentiate Gram-positive bacteria from Gram-negative bacteria.
Rationale:
1. Gram-positive bacteria retain the crystal violet stain due to their thick peptidoglycan layer.
2. This thick layer provides structural support and protection to the cell.
3. Gram-positive bacteria lack an outer membrane, which is a feature of Gram-negative bacteria (Choice A).
4. Thin peptidoglycan layer is a characteristic of Gram-negative bacteria, not Gram-positive (Choice B).
5. Presence of LPS (lipopolysaccharide) is a feature of Gram-negative bacteria, not Gram-positive (Choice D).
In summary, the presence of a thick peptidoglycan layer is a characteristic feature of Gram-positive
A sputum smear stained by Gram's method revealed Gram-positive cocci in clusters. The patient presented with an abscess. What is the causative agent?
- A. Staphylococcus aureus
- B. Streptococcus pyogenes
- C. Enterococcus faecalis
- D. Micrococcus luteus
Correct Answer: A
Rationale: The correct answer is A: Staphylococcus aureus. Staphylococcus aureus is a Gram-positive bacterium that commonly presents as cocci in clusters. It is a known causative agent of abscesses due to its ability to produce enzymes and toxins that contribute to tissue destruction. In this case, the presence of Gram-positive cocci in clusters aligns with the characteristic morphology of Staphylococcus aureus.
Summary of incorrect choices:
B: Streptococcus pyogenes is a Gram-positive bacterium that typically presents as cocci in chains, not clusters. It is more commonly associated with pharyngitis and skin infections rather than abscesses.
C: Enterococcus faecalis is a Gram-positive bacterium that typically presents as cocci in pairs or short chains, not clusters. It is more commonly associated with urinary tract infections and endocarditis.
D: Micrococcus luteus is a Gram-positive bacterium that typically presents as t
Which of the following microorganisms require a moist environment to survive and most often live in ponds, streams, lakes, and oceans?
- A. Mycorrhizae
- B. Armillaria gallica
- C. Blastospores
- D. Blastospores
Correct Answer: D
Rationale: The correct answer is D: Blastospores. Blastospores are a type of fungal spore that requires a moist environment to survive. They are commonly found in water bodies like ponds, streams, lakes, and oceans. Mycorrhizae (A) are symbiotic associations between fungi and plant roots, not solely dependent on a moist environment. Armillaria gallica (B) is a type of fungus that can survive in various environmental conditions, not specifically reliant on a moist environment. Choice C is a duplicate of Blastospores, making it incorrect.
Which of the following diseases is transmitted via aerosols?
- A. Psittacosis
- B. Shigellosis
- C. Leptospirosis
- D. Giardiasis
Correct Answer: A
Rationale: The correct answer is A: Psittacosis. This disease is transmitted via aerosols containing dried bird droppings or respiratory secretions from infected birds. When these aerosols are inhaled, the bacteria causing psittacosis enter the respiratory system and infect the individual.
- B: Shigellosis is transmitted through contaminated food or water, not via aerosols.
- C: Leptospirosis is transmitted through contact with water, soil, or food contaminated with the urine of infected animals, not via aerosols.
- D: Giardiasis is transmitted through ingesting contaminated food or water, not via aerosols.
Therefore, Psittacosis is the only disease in the list that is transmitted via aerosols, making it the correct answer.