microbiology chapter 1 test bank

Correct Answer: B

Rationale: The correct answer is B: Streptococcus mutans. This bacterium is associated with the formation of dental caries due to its ability to metabolize sugars and produce acids that demineralize tooth enamel. Streptococcus pneumoniae (choice A) is not typically associated with dental caries. Bacillus anthracis (choice C) causes anthrax, not dental caries. Clostridium botulinum (choice D) causes botulism, not dental caries. Streptococcus mutans' unique characteristics make it the correct choice for the bacteria associated with dental caries.

Correct Answer: A

Rationale: Rationale: 1. Endo agar inhibits the growth of Gram-positive bacteria. 2. Colorless colonies on Endo agar indicate lactose non-fermenting bacteria. 3. Shigella dysenteriae is a lactose non-fermenting, Gram-negative rod, causing dysentery. 4. Salmonella typhi, Escherichia coli, and Proteus vulgaris are lactose fermenters, so they would produce pink colonies on Endo agar. Therefore, the most likely causative agent is Shigella dysenteriae.

Correct Answer: B

Rationale: The correct answer is B: peak effect. When drug receptors are maximally activated, it means the drug has reached its highest effectiveness, resulting in the peak effect. This occurs when the drug concentration is at its highest level in the body, leading to the maximum response. Threshold level (A) refers to the minimum amount of drug needed to produce a response. Cessation effect (C) is when the drug's effect wears off. Latency time (D) is the time it takes for the drug to start producing an effect. So, the peak effect best describes the scenario where drug receptors are maximally activated.

Correct Answer: A

Rationale: The correct answer is A because spores are heat-resistant and require high temperatures for destruction. Autoclaving at 121�C for 15-20 minutes ensures spore destruction due to the high pressure and temperature. Choice B (heating to 80�C) is insufficient to destroy spores. Choice C (boiling at 100�C for 10 minutes) is also inadequate as spores require higher temperatures for elimination. Choice D (None of them) is incorrect as autoclaving is the standard method for spore sterilization.

Correct Answer: A

Rationale: The correct answer is A: Ciprofloxacin. Pseudomonas aeruginosa is commonly resistant to Ampicillin, Cefazolinum, and Azithromycin. Ciprofloxacin is a fluoroquinolone antibiotic known for its efficacy against Pseudomonas aeruginosa. Its broad spectrum and ability to penetrate tissues make it the most advisable choice for treating secondary obstructive pyelonephritis caused by this pathogen.