microbiology basic and clinical principles test bank

Correct Answer: C

Rationale: The correct answer is C: the hydrolysis of the four-membered ring present in penicillin. Beta-lactamase enzyme catalyzes the hydrolysis of the four-membered beta-lactam ring present in penicillin, rendering the antibiotic ineffective against bacterial cell walls. This enzyme breaks the bond in the beta-lactam ring, thus inactivating the antibiotic. Incorrect choices: A: the final cross-linking reaction to form the bacterial cell wall - This is incorrect as beta-lactamase does not participate in the formation of bacterial cell walls. B: the biosynthesis of the penicillin structure from the amino acid valine and cysteine - This is incorrect as beta-lactamase is not involved in the biosynthesis of penicillin. D: the hydrolysis of the acyl side chain from penicillin structures - This is incorrect as beta-lactamase specifically targets the beta-lactam ring, not the

Correct Answer: B

Rationale: The capsule of Bacillus anthracis is made of polypeptide. This is because the capsule is composed of a protein-based material that surrounds the bacterium, providing protection and aiding in its virulence. Polysaccharides, lipids, and the absence of capsules are not characteristic of Bacillus anthracis' capsule structure, making choices A, C, and D incorrect, respectively.

Correct Answer: C

Rationale: The correct answer is C: young adults. Young adults are at a higher risk for sexually transmitted infections (STIs) due to factors such as engaging in risky sexual behaviors, lack of awareness, and inconsistent condom use. They are more likely to have multiple sexual partners and are less likely to seek regular STI screenings. Adolescents, while also at risk, may not make up almost half of all STI cases in the U.S. The elderly, on the other hand, are generally at a lower risk due to lower levels of sexual activity compared to young adults.

Correct Answer: B

Rationale: The correct answer is B: Shigella. On Endo agar, Shigella appears as colorless colonies due to its inability to ferment lactose. Shigella is a Gram-negative rod and is a common cause of diarrhea. Salmonella (A) and Escherichia coli (C) would typically produce pink colonies on Endo agar as they can ferment lactose. Proteus (D) is not commonly associated with diarrhea and would not be expected to grow on Endo agar.

Correct Answer: B

Rationale: The correct answer is B: protein filaments made of flagellin. Bacterial flagella are composed of flagellin proteins arranged in helical filaments. This structure allows for movement and propulsion of bacteria. A: 9+2 microtubule arrangement is incorrect because this structure is typically found in eukaryotic flagella, not bacterial flagella. C: Lipid bilayer is incorrect as it is a structural component of cell membranes, not bacterial flagella. D: Peptidoglycan layer is incorrect as it is a component of bacterial cell walls, not flagella.