The stain used to identify bacteria with a large amount of peptidoglycan in their cell walls is the:

Correct Answer: C

Rationale: The correct answer is C: Negative stain. Negative staining uses acidic dyes which are repelled by the bacterial cell wall components, highlighting bacteria with a large amount of peptidoglycan. Acid-fast stain (A) is used to identify Mycobacterium species with waxy cell walls. Gram stain (B) differentiates bacteria into Gram-positive and Gram-negative based on cell wall composition. Option D is a duplicate of option C and is incorrect.

Correct Answer: B

Rationale: The correct answer is B: Staphylococcus aureus. This bacteria is known to cause skin infections and toxic shock syndrome due to its ability to produce toxins that can lead to severe symptoms. Staphylococcus aureus is commonly found on the skin and can enter the body through cuts or wounds, causing infections. Other choices are incorrect because Pseudomonas aeruginosa typically causes infections in immunocompromised individuals, Micrococcus luteus is a common skin bacterium that is not typically pathogenic, and Propionibacterium acnes is associated with acne, not skin infections or toxic shock syndrome.

Correct Answer: C

Rationale: The correct answer is C: rotaviruses. Rotaviruses are the most common cause of infectious diarrhea in infants and children due to their highly contagious nature and ability to spread easily in childcare settings. They are known to cause severe diarrhea, vomiting, and dehydration in young children. Noroviruses (A), adenoviruses (B), and caliciviruses (D) can also cause diarrhea, but rotaviruses are specifically known for their prevalence and severity in the pediatric population. This is why C is the correct answer.

Correct Answer: D

Rationale: The correct answer is D: rabbit fever. Tularemia is commonly known as rabbit fever due to the fact that it is often contracted through handling infected rabbits or other rodents. This zoonotic disease is caused by the bacterium Francisella tularensis. Scarlet fever (A) is a streptococcal infection characterized by a rash, not related to tularemia. Strep throat (B) is a bacterial infection caused by Streptococcus bacteria and is not associated with tularemia. Cat scratch fever (C) is caused by Bartonella henselae and typically transmitted through cat scratches or bites, not related to tularemia.

Correct Answer: B

Rationale: The correct answer is B: acidic pH. The reproductive tract's acidic pH serves as a defense mechanism by creating an environment hostile to many pathogens, preventing microbial infection. The acidic pH helps to inhibit the growth and survival of harmful microorganisms. A: Alkaline pH would actually be more favorable for microbial growth as most pathogens thrive in neutral to alkaline pH environments. C: High sugar concentration can actually promote microbial growth as many pathogens feed on sugars. D: High body temperature may help in some cases, but it is not as effective as an acidic pH in preventing microbial infection in the reproductive tract.