microbiology an introduction test bank

Correct Answer: A

Rationale: The correct answer is A: Clostridium perfringens. This bacterium is a Gram-positive rod that forms chains and produces gas due to its ability to ferment carbohydrates. It is also spore-forming, which helps it survive harsh conditions. Clostridium perfringens is commonly associated with severe tissue infections and gas gangrene. Choice B: Bacillus anthracis is also a spore-forming Gram-positive rod but is not typically associated with gas production or severe tissue infections. Choice C: Clostridium tetani is a spore-forming bacterium that causes tetanus, not severe tissue infections with gas production. Choice D: Pseudomonas aeruginosa is a Gram-negative bacterium and does not fit the description provided in the question.

Correct Answer: B

Rationale: Rationale: 1. Streptococcus pyogenes is the causative agent of strep throat. 2. If untreated, strep throat can lead to rheumatic fever. 3. Rheumatic fever is an autoimmune complication of streptococcal infections. 4. E. coli, S. epidermidis, and S. aureus are not typically associated with rheumatic fever.

Correct Answer: B

Rationale: The correct answer is B because filoviruses, such as Ebola virus, require investigation in specifically equipped laboratories with high biological protection due to their high pathogenicity and risk of transmission. This is essential for ensuring the safety of researchers and preventing outbreaks. A: This is incorrect as filoviruses are not the most common cause of gastroenteritis; they primarily cause severe hemorrhagic fevers. C: Filoviruses are not widespread; they are typically confined to specific regions during outbreaks. D: Mass immunization is not used for filoviruses as there is no established vaccine for general prophylaxis.

Correct Answer: A

Rationale: The correct answer is A: Giardia lamblia. Giardia lamblia is a protozoan parasite that causes foul-smelling diarrhea. The trophozoites of Giardia lamblia have two nuclei and flagella, which are characteristic features seen on stool microscopy. The presence of these specific features helps differentiate Giardia lamblia from the other options. Entamoeba histolytica (B) typically presents with one nucleus and lacks flagella. Trichomonas vaginalis (C) is a sexually transmitted parasite with a different morphology. Balantidium coli (D) is a ciliated parasite, not flagellated like Giardia lamblia.

Correct Answer: B

Rationale: The correct answer is B (2). During glycolysis, one glucose molecule is broken down into two molecules of pyruvate. In this process, a net gain of 2 ATP molecules is produced through substrate-level phosphorylation. Specifically, ATP is generated during the conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate and during the conversion of phosphoenolpyruvate to pyruvate. The other choices are incorrect because the net gain of ATP molecules in glycolysis is not 1, 3, or 4; it is 2 based on the specific enzymatic reactions involved in the pathway.