microbiology an evolving science test bank

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pyogenes. The presence of Gram-positive cocci in chains suggests a streptococcal infection. Beta-hemolysis indicates the production of a hemolysin that lyses red blood cells, a characteristic of Streptococcus pyogenes. This bacterium is known to cause strep throat and can present with fever and sore throat. Summary: - B: Streptococcus pneumoniae is a common cause of pneumonia but typically appears as lancet-shaped cocci, not in chains. - C: Staphylococcus aureus is a gram-positive cocci in clusters, not chains, and is not typically beta-hemolytic. - D: Enterococcus faecalis is a gram-positive cocci that are part of the normal gut flora and are not typically beta-hemolytic or found in chains.

Correct Answer: A

Rationale: The correct answer is A: Actinomycosis. This is a chronic bacterial infection caused by Actinomyces species. In this case, the description of dense yellow-green colored focus, white granules in purulent masses, and presence of fungal druses, plasma cells, xanthome cells, and macrophages all match the characteristics of actinomycosis. Actinomycosis typically presents with abscess formation containing sulfur granules, which are yellowish and granular. The other choices (B: Furuncle, C: Carbuncle, D: Syphilis) do not fit the clinical and histological features described in the question, making them incorrect options.

Correct Answer: A

Rationale: The correct answer is A: Lassa virus. The rationale is as follows: 1. Lassa virus is a member of the Arenaviridae family, known for causing Lassa fever. 2. Arenaviridae family includes viruses with a segmented genome and are transmitted through rodents. 3. Crimean-Congo hemorrhagic fever virus (Choice B) belongs to the Bunyaviridae family, not Arenaviridae. 4. Rabies virus (Choice C) belongs to the Rhabdoviridae family, not Arenaviridae. 5. Epstein-Barr virus (Choice D) belongs to the Herpesviridae family, not Arenaviridae. In summary, Lassa virus is the correct choice as it aligns with the characteristics of the Arenaviridae family, while the other choices belong to different virus families.

Correct Answer: A

Rationale: The correct answer is A (Escherichia coli, Gardnerella vaginalis, and Staphylococcus aureus) because they are known to commonly cause nonsexually transmitted infections of the reproductive system. Escherichia coli can cause urinary tract infections that can ascend to the reproductive system. Gardnerella vaginalis is associated with bacterial vaginosis, a common infection of the vagina. Staphylococcus aureus can cause infections in the reproductive system through various means. Choices B, C, and D are incorrect: B: Streptococcus faecalis, Klebsiella oxytoca, and Serratia marcescens are not commonly associated with reproductive system infections. C: Clostridium tetani and Bacillus cereus are not typically involved in reproductive system infections. D: Neisseria gonorrhoeae causes sexually transmitted infections, Helicobacter pylori causes gastrointestinal issues, and Pseudomonas aeruginosa is more

Correct Answer: A

Rationale: The correct answer is A: Commensalism. In this relationship, the skin microflora benefits from the host without causing harm or benefitting it. This is evident in the mutualistic interaction where the microflora receive nutrients and a place to live, while the host remains unaffected. Choice B, Infection, is incorrect because it implies harm to the host. Choice C, Parasitism, is also incorrect as it involves one organism benefiting at the expense of the other. Choice D, No correct answer, is not applicable here as Commensalism accurately describes the relationship between the macroorganism and skin microflora.