mcgraw hill microbiology test bank

Correct Answer: B

Rationale: The correct answer is B: Vibrio cholerae. Cholera is caused by Vibrio cholerae, a gram-negative bacterium that produces a toxin leading to severe watery diarrhea. Shigella dysenteriae causes dysentery, not cholera. Salmonella enterica causes salmonellosis, not cholera. Clostridium perfringens is associated with food poisoning, not cholera. In summary, Vibrio cholerae is the correct answer because it is the specific bacterium known to cause cholera, while the other choices are associated with different diseases.

Correct Answer: A

Rationale: Step 1: Gram-negative bacillus indicates P. aeruginosa, known for causing wound infections. Step 2: Semi-transparent mucous colonies of blue-green color with a pearlescent appearance are characteristic of P. aeruginosa. Step 3: Specific odor of violets or jasmine is a unique feature of P. aeruginosa. Therefore, the correct answer is A: P. aeruginosa. Summary: - B: P. vulgaris typically forms yellow colonies and doesn't have the characteristic odor. - C: S. aureus forms creamy white colonies, not blue-green, and has a distinct odor. - D: S. pyogenes forms grayish-white colonies and doesn't have the unique characteristics described.

Correct Answer: B

Rationale: The correct answer is B: Borrelia burgdorferi. Borrelia burgdorferi is the bacteria responsible for causing Lyme disease. It is transmitted to humans through the bite of infected black-legged ticks. Treponema pallidum causes syphilis, Leptospira interrogans causes leptospirosis, and Rickettsia rickettsii causes Rocky Mountain spotted fever. Borrelia burgdorferi is specifically associated with Lyme disease due to its transmission through tick bites and the characteristic symptoms it causes.

Correct Answer: C

Rationale: The correct answer is C: beaded. In an agar slant, beaded colonies appear as separate or semiconfluent, forming small, round colonies with gaps between them. This term accurately describes the appearance of the colonies in this context. A: Filiform colonies are dense and opaque with smooth edges, not separate or semiconfluent. B: Echinulate colonies have spiny projections, not the characteristic of separate or semiconfluent growth. D: Effuse colonies spread out extensively and lack defined borders, unlike the distinct appearance of separate or semiconfluent colonies.

Correct Answer: A

Rationale: The correct answer is A: Anaerobic infection. The sudden deterioration, bursting pain, edema, foul appearance of wound, and presence of gas are indicative of gas gangrene caused by anaerobic bacteria like Clostridium perfringens. These bacteria thrive in low oxygen environments, such as deep wound tissues. The symptoms align with the classic presentation of gas gangrene, necessitating immediate surgical intervention. Choice B: Aerobic gram-negative, is incorrect because anaerobic bacteria, not aerobic gram-negative bacteria, are responsible for gas gangrene. Choice C: Putrid, is incorrect as it is a general term referring to foul-smelling decay and does not specify the type of infection. Choice D: Aerobic gram-positive, is incorrect as gas gangrene is typically caused by anaerobic bacteria, not aerobic gram-positive bacteria.