foundations in microbiology test bank

Correct Answer: D

Rationale: The correct answer is D: Fungi do not stain in the gram staining method because they have a unique cell wall composition different from bacteria. Fungi have chitin in their cell walls, which is not easily stained by the gram staining process. This method primarily targets the peptidoglycan layer present in bacterial cell walls. Therefore, fungi will not take up the stain and will remain colorless. The other choices (A: Blue-purple, B: Red, C: Silver) are incorrect because they describe colors that are associated with staining results for bacteria, not fungi.

Correct Answer: C

Rationale: The correct answer is C: enterotoxigenic E. Coli (ETEC). ETEC adheres to the intestine wall and produces toxins, leading to symptoms like diarrhea. Shigella spp. invade intestinal cells, Salmonella spp. cause inflammation, and Helicobacter pylori infects the stomach lining. This makes them incorrect choices for bacteria adhering to the intestine wall and producing toxins.

Correct Answer: C

Rationale: The correct answer is C: Streptococcus pyogenes. This bacterium is commonly known as "flesh-eating bacteria" due to its ability to cause severe tissue destruction and necrotizing fasciitis. Streptococcus pyogenes produces toxins that break down skin and muscle tissues. Staphylococcus aureus (A) can cause skin infections but is not typically associated with necrotizing fasciitis. Staphylococcus epidermidis (B) is a normal skin flora and rarely causes infections. Propionibacterium acnes (D) is associated with acne and not known for causing tissue destruction. Therefore, the correct choice is Streptococcus pyogenes due to its unique ability to cause severe tissue damage and necrotizing fasciitis.

Correct Answer: C

Rationale: The correct answer is C: Plague. Yersinia pestis is the bacterium responsible for causing the bubonic, septicemic, and pneumonic plague. The bacterium is transmitted to humans through infected flea bites or handling infected animals. Tonsillitis (A) is commonly caused by streptococcal bacteria, leprosy (B) is caused by Mycobacterium leprae, and rat fever (D) is another term for leptospirosis, caused by Leptospira bacteria.

Correct Answer: D

Rationale: The correct answer is D, "All of the above." Staphylococcus aureus, Escherichia coli, and Neisseria meningitidis all produce endotoxins that can lead to septic shock. Endotoxins are part of the outer membrane of Gram-negative bacteria, such as E. coli and N. meningitidis, which can trigger a severe immune response leading to septic shock. S. aureus, a Gram-positive bacterium, produces toxins that can also contribute to septic shock. Therefore, all of these bacteria can produce endotoxins responsible for septic shock. Choices A, B, and C are incorrect because they only identify individual bacteria that produce endotoxins, whereas the correct answer encompasses all bacteria listed.