microbiology chapter 14 test bank

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pyogenes. Rationale: 1. Gram-positive cocci in pairs suggest Streptococcus species. 2. Catalase-negative rules out Staphylococcus. 3. Beta-hemolytic indicates Streptococcus pyogenes due to its beta-hemolytic properties. Summary: B: Streptococcus pneumoniae is catalase-negative but not beta-hemolytic. C: Enterococcus faecalis is not typically beta-hemolytic. D: Staphylococcus aureus is catalase-positive and not typically in pairs.

Correct Answer: D

Rationale: The correct answer is D because all three bacteria listed (Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa) can produce endotoxins that can lead to septic shock. Endotoxins are lipopolysaccharides found in the outer membrane of Gram-negative bacteria like E. coli and P. aeruginosa. Staphylococcus aureus, a Gram-positive bacterium, can also produce endotoxins called superantigens that can trigger a massive immune response leading to septic shock. Therefore, all of the above choices are correct. Choices A, B, and C alone are incorrect because they do not account for the fact that all three bacteria listed produce endotoxins that can cause septic shock.

Correct Answer: C

Rationale: The correct answer is C: plasmids. Plasmids are nonchromosomal DNA molecules commonly found in bacterial cells, providing additional genetic material for bacteria. They are not essential for bacterial survival but can confer advantages such as antibiotic resistance. Endospores (A) are dormant bacterial structures resistant to harsh conditions. Transposons (B) are mobile genetic elements that can move within a genome. Prions (D) are misfolded proteins causing neurodegenerative diseases, not DNA molecules.

Correct Answer: A

Rationale: The correct answer is A: Staphylococcus aureus. This bacterium is Gram-positive cocci in clusters, catalase-positive, and coagulase-positive. Staphylococcus aureus is a common pathogen causing abscesses. Streptococcus pyogenes (B) is Gram-positive cocci in chains, not clusters. Micrococcus luteus (C) is catalase-positive but coagulase-negative. Enterococcus faecalis (D) is catalase-negative and coagulase-negative.

Correct Answer: A

Rationale: Step-by-step rationale for why choice A is correct: 1. Helicobacter pylori, the bacteria causing helicobacteriosis, is microaerophilic, requiring low oxygen levels. 2. Cultivation conditions must mimic the natural environment of the bacteria. 3. Failure to provide a microaerophilic environment can hinder bacterial growth. 4. Thus, the ability to cultivate these bacteria requires consideration of their microaerophilic nature. Summary: - Choice A is correct because Helicobacter pylori is a microaerophilic bacteria. - Choice B (Presence of urease) is incorrect as it is a characteristic used for diagnosis, not cultivation. - Choice C (Absence of spores and capsules) is incorrect as it does not relate to cultivation requirements. - Choice D (Colonization of gastral cells) is incorrect as it pertains to bacterial behavior, not cultivation needs.