microbiology basic and clinical principles test bank

Correct Answer: B

Rationale: The correct answer is B: Clostridium botulinum. This bacterium belongs to the Clostridium genus, known for its ability to produce endospores. Endospores are dormant, resistant structures that help bacteria survive harsh conditions. Staphylococcus aureus (A), Escherichia coli (C), and Neisseria gonorrhoeae (D) do not produce endospores. Staphylococcus aureus is a gram-positive bacterium known for causing various infections, but it does not form endospores. Escherichia coli is a gram-negative bacterium commonly found in the intestines of humans and animals, but it does not produce endospores. Neisseria gonorrhoeae is a gram-negative bacterium that causes the sexually transmitted infection gonorrhea, but it also does not form endospores.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pneumoniae. The description of Gram-positive cocci in pairs with pointed ends and capsules matches the morphology of S. pneumoniae. This bacterium is known to cause pneumonia, especially in individuals with underlying conditions like COPD. Staphylococcus aureus (B) typically appears in clusters, not pairs. Klebsiella pneumoniae (C) is a Gram-negative rod, not a cocci. Neisseria meningitidis (D) is a Gram-negative diplococcus, not a cocci. Hence, based on the morphology and clinical context, Streptococcus pneumoniae is the likely microorganism causing pneumonia in this patient.

Correct Answer: D

Rationale: Rationale: After a splenectomy, patients are at high risk of infections caused by encapsulated bacteria such as Streptococcus pneumoniae, Listeria monocytogenes, and Salmonella. The spleen plays a crucial role in the immune response against encapsulated bacteria, and its absence increases susceptibility to these specific pathogens. Therefore, all choices are correct as patients are at risk of infections from all three types of bacteria mentioned.

Correct Answer: D

Rationale: The correct answer is D (All of the above) because all three bacteria listed produce exotoxins that cause severe gastrointestinal illness. Clostridium botulinum produces botulinum toxin causing botulism. Vibrio cholerae produces cholera toxin leading to cholera. Escherichia coli can produce various exotoxins causing different types of severe gastrointestinal illnesses like E. coli O157:H7 causing bloody diarrhea. Therefore, all choices A, B, and C are correct in this case as they all produce exotoxins causing severe gastrointestinal illness.

Correct Answer: B

Rationale: The correct answer is B: Clostridium botulinum. This bacterium belongs to the Clostridium genus, known for its ability to produce endospores. Endospores are dormant, resistant structures that help bacteria survive harsh conditions. Staphylococcus aureus (A), Escherichia coli (C), and Neisseria gonorrhoeae (D) do not produce endospores. Staphylococcus aureus is a gram-positive bacterium known for causing various infections, but it does not form endospores. Escherichia coli is a gram-negative bacterium commonly found in the intestines of humans and animals, but it does not produce endospores. Neisseria gonorrhoeae is a gram-negative bacterium that causes the sexually transmitted infection gonorrhea, but it also does not form endospores.