McGraw Hill Microbiology Test Bank

Correct Answer: A

Rationale: The correct answer is A: Bacterial DNA. PCR analysis detects specific DNA sequences, so a positive result for H. pylori indicates the presence of the bacterial DNA in the gastric biopsy specimen. This method identifies the genetic material of the bacterium, not the bacterium itself (choice C) or its toxins (choice B). Additionally, PCR does not directly detect bacterial enzymes (choice D) but rather focuses on genetic material for accurate identification. Therefore, in this case, the detection of H. pylori in the PCR analysis points to the presence of bacterial DNA, confirming the etiology of peptic ulcer disease.

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.

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: B

Rationale: The correct answer is B: Personal eyewash. Personal eyewash is designed for immediate flushing until the victim reaches a more suitable safety unit. It provides a controlled flow of water to safely flush eyes while transporting the victim. The emergency shower (A) is meant for full-body coverage, not just for the eyes. Handheld drench hose (C) may not provide adequate flushing pressure. Combination unit (D) may not be easily portable for immediate use.

Correct Answer: D

Rationale: The correct answer is D: components of the gram-negative cell wall. Bacterial endotoxins are lipopolysaccharides found in the outer membrane of gram-negative bacteria. They are released upon bacterial cell lysis and can cause severe immune responses. A: Proteins in the cell wall - This is incorrect because endotoxins are not proteins but rather lipopolysaccharides. B: Secreted into the environment - Endotoxins are not actively secreted but are released upon cell death or lysis. C: Components of the gram-positive cell wall - Gram-positive bacteria do not have an outer membrane with lipopolysaccharides, so endotoxins are not found in the gram-positive cell wall.