microbiology an evolving science test bank

Correct Answer: C

Rationale: The correct answer is C: Direct transfer of DNA between two bacterial cells. In bacterial conjugation, genetic material is transferred directly from one bacterial cell to another through a conjugative pilus. This process involves physical contact between the cells, followed by the transfer of plasmid DNA or chromosomal DNA. This mechanism allows for the exchange of genetic information between bacteria, leading to genetic diversity. Explanation of why other choices are incorrect: A: DNA transfer via bacteriophage - Bacteriophage is a virus that infects bacteria and transfers its genetic material, but this is not the mechanism involved in bacterial conjugation. B: Uptake of naked DNA from the environment - This process is known as transformation, where bacteria take up free DNA from the environment, but it is not specific to bacterial conjugation. D: Binary fission - Binary fission is a form of asexual reproduction in bacteria where a single cell divides into two identical cells, and it is not related to the process

Correct Answer: A

Rationale: The correct answer is A: Shigella dysenteriae. Shigella causes dysentery, characterized by bloody diarrhea and abdominal pain. Shigella is a non-lactose-fermenting, Gram-negative rod. B: Salmonella typhi causes typhoid fever, not typically associated with abdominal pain and diarrhea. C: Escherichia coli, a common gut bacteria, can cause diarrhea but typically ferments lactose. D: Proteus vulgaris is not a common cause of gastrointestinal infection and is not typically associated with abdominal pain and diarrhea.

Correct Answer: B

Rationale: The correct answer is B: colonization. E. Coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa in the pharynx indicate colonization rather than being part of the normal resident flora. Colonization refers to the presence of these bacteria on body surfaces without causing harm. They are not considered normal flora in the pharynx but rather transient or opportunistic pathogens. Choice A is incorrect because these bacteria are not part of the normal resident flora of the pharynx. Choice C is incorrect as it implies that these bacteria are both normal flora and colonization, which is not accurate. Choice D is incorrect as there is evidence of bacterial presence, indicating colonization.

Correct Answer: A

Rationale: The correct answer is A: Aspergillosis and candidiasis. Galactomannan is a polysaccharide found in Aspergillus cell walls and is detected in patients with invasive aspergillosis. Free mannan is a polysaccharide found in Candida cell walls and is detected in patients with candidiasis. Therefore, detection of galactomannan and free mannan is specific for diagnosing Aspergillosis and candidiasis. Choices B, C, and D are incorrect as HIV infection, syphilis, and leptospirosis do not involve the detection of galactomannan or free mannan for diagnosis.

Correct Answer: B

Rationale: The correct answer is B: scalp. Tinea capitis is a fungal infection that specifically affects the scalp. This infection is caused by dermatophytes, which thrive in warm and moist environments. It typically presents with symptoms such as scaling, itching, and hair loss on the scalp. Choices A, C, and D are incorrect because tinea pedis (athlete's foot) affects the feet, oral thrush is a fungal infection of the mouth, and tinea manuum affects the hands. By process of elimination and understanding the specific characteristics of tinea capitis, we can determine that the scalp is the correct location for this fungal infection.