medical microbiology test bank

Correct Answer: A

Rationale: The correct answer is A: Propionibacterium shermanii. This bacterium is used in the production of certain types of cheese, such as Swiss cheese, to create the characteristic holes and flavor. Propionibacterium produces carbon dioxide gas during fermentation, forming the holes in the cheese. Acetobacter aceti (B) is used in vinegar production. Giardia (C) is a parasite that causes gastrointestinal issues, not used in cheese production. Fusobacterium (D) is a type of bacteria associated with infections in humans, not used in cheese production.

Correct Answer: B

Rationale: The correct answer is B: autoclaving. Autoclaving is a process that uses high pressure and steam to achieve temperatures above the boiling point of water, typically around 121-134�C. This high heat and pressure are effective in destroying spore forms of microorganisms, which are highly resistant structures that can withstand boiling temperatures. Autoclaving ensures the complete destruction of spores, making it an effective method for sterilization. Rationale: A: Pasteurization uses lower heat compared to autoclaving and is not sufficient to destroy spore forms. C: Freezing does not effectively destroy spore forms, as most microorganisms can survive freezing temperatures. D: Boiling, while effective for many microorganisms, may not be sufficient to destroy spore forms due to their high resistance, unlike autoclaving.

Correct Answer: A

Rationale: The correct answer is A: Treponema pallidum. This bacterium is responsible for causing syphilis due to its unique spiral shape and ability to penetrate mucous membranes. It is transmitted through sexual contact or from mother to fetus. Neisseria gonorrhoeae causes gonorrhea, Chlamydia trachomatis causes chlamydia, and Escherichia coli is a common bacterium in the gastrointestinal tract. Syphilis is distinct due to its characteristic symptoms and stages, making Treponema pallidum the correct choice.

Correct Answer: B

Rationale: The correct answer is B: Fluconazole. Rationale: 1. Candidiasis is a fungal infection, so an antimycotic agent is needed. 2. β-lactam antibiotics like ampicillin can lead to fungal overgrowth, necessitating an antimycotic. 3. Fluconazole is an antifungal agent effective against Candida species. 4. Streptomycin is an antibiotic, not an antifungal. 5. Phthalylsulfathiazole is an antibacterial sulfonamide, not an antifungal. 6. Ampicillin is an antibiotic, not an antifungal.

Correct Answer: D

Rationale: The correct answer is D because antigenic shift is a major change in the influenza virus where genetic material from different influenza viruses mix to create a new subtype. This is a large-scale change that results in a novel virus with a different antigenic composition. Option A and B are incorrect because antigenic shift does involve the exchange of genetic information between animal and human influenza A viruses, and it does occur when animal or avian influenza viruses of type A directly pass into the human population. Option C is incorrect because antigenic shift is not related to the recirculation of a previously circulating influenza strain.