Nokea
Which bacteria are capable of producing spores that can survive extreme environmental conditions?
- A. Clostridium botulinum
- B. Bacillus anthracis
- C. Both A and B
- D. None of the above
Correct Answer: C
Rationale: The correct answer is C (Both A and B) because both Clostridium botulinum and Bacillus anthracis are capable of producing spores. Spores are highly resistant structures that allow bacteria to survive harsh environmental conditions. Clostridium botulinum and Bacillus anthracis produce spores as a survival mechanism when conditions become unfavorable. Choice A (Clostridium botulinum) is incorrect because it only represents one of the bacteria capable of producing spores. Choice B (Bacillus anthracis) is also incorrect as it alone does not encompass all bacteria capable of producing spores. Choice D (None of the above) is incorrect as both bacteria mentioned can produce spores.
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A patient with a productive cough and fever had a Gram-positive cocci isolated from a sputum sample. The bacteria were catalase-positive and coagulase-negative. What is the likely microorganism?
- A. Staphylococcus epidermidis
- B. Staphylococcus aureus
- C. Streptococcus pneumoniae
- D. Neisseria meningitidis
Correct Answer: A
Rationale: The correct answer is A: Staphylococcus epidermidis.
1. Gram-positive cocci suggest a staphylococcal species.
2. Catalase-positive indicates it belongs to the Staphylococcus genus.
3. Coagulase-negative rules out Staphylococcus aureus.
4. Staphylococcus epidermidis is a common cause of infections in immunocompromised patients.
Summary:
- B: Staphylococcus aureus is coagulase-positive.
- C: Streptococcus pneumoniae is a Gram-positive diplococci.
- D: Neisseria meningitidis is a Gram-negative diplococci.
An example of selective media is:
- A. McConkey agar
- B. Bordet Gengou agar
- C. Peptone water
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A: McConkey agar. Selective media selectively inhibit the growth of certain organisms while allowing others to grow. McConkey agar contains crystal violet and bile salts that inhibit the growth of Gram-positive bacteria, making it selective for Gram-negative bacteria. Choices B and C are not selective media, as they do not specifically inhibit the growth of certain types of bacteria. Choice D is incorrect as McConkey agar is indeed an example of selective media.
Which one of the following is a normal skin flora?
- A. Streptococcus pyogenes
- B. Staphylococcus epidermidis
- C. Pseudomonas aeruginosa
- D. Acinetobacter baumannii
Correct Answer: B
Rationale: The correct answer is B: Staphylococcus epidermidis. This bacterium is a normal skin flora commonly found on human skin. It is part of the skin microbiota and helps protect against pathogenic organisms. Streptococcus pyogenes (A), Pseudomonas aeruginosa (C), and Acinetobacter baumannii (D) are not normal skin flora. Streptococcus pyogenes is a pathogenic bacterium causing various infections, Pseudomonas aeruginosa is an opportunistic pathogen commonly found in water and soil, and Acinetobacter baumannii is associated with healthcare-associated infections.
The specific binding of HIV to the CD4 surface molecules of the target cells is brought about by:
- A. Gp120
- B. Gp41
- C. Gp32
- D. Gp55
Correct Answer: A
Rationale: The correct answer is A: Gp120. Gp120 is a glycoprotein on the surface of the HIV virus that specifically binds to the CD4 receptor on target cells. This binding is essential for the virus to enter the host cell and initiate the infection process. Gp41 is another glycoprotein on the virus that helps with membrane fusion, not binding to CD4. Gp32 and Gp55 are not involved in the specific binding of HIV to CD4 molecules. So, A is correct as it directly plays a key role in the initial attachment of HIV to target cells.
Specify the FALSE statement. Bacteriocins:
- A. Kill the bacterial cells of closely related species
- B. Are substances with protein nature
- C. Are polysaccharides of varying activity
- D. Kill the bacteria cells of other strains of the same species
Correct Answer: C
Rationale: The correct answer is C because bacteriocins are substances with protein nature, not polysaccharides. Bacteriocins are antimicrobial peptides that kill bacterial cells, mainly those of closely related species or other strains of the same species. Polysaccharides are not typically involved in bacteriocin activity. Therefore, option C is false. Options A, B, and D are true statements supported by the nature and function of bacteriocins.