Foundations in Microbiology Test Bank

Correct Answer: A

Rationale: Rationale for Correct Answer A (Diphtheria): 1. Thin yellow bacilli with dark brown grains on ends suggest Corynebacterium diphtheriae, characteristic of diphtheria. 2. Roman numeral five shape is typical of diphtheria bacilli. 3. Diphtheria causes sore throat and can spread in boarding schools. 4. Neisser staining method is used for diphtheria bacilli. Summary of Incorrect Choices: B: Scarlet fever is caused by Streptococcus pyogenes and presents with rash, not yellow bacilli. C: Listeriosis is caused by Listeria monocytogenes, not consistent with the described findings. D: Tonsillitis can be caused by various bacteria or viruses, but the specific characteristics described do not match.

Correct Answer: D

Rationale: After the transfer of the F plasmid from the donor to the recipient cell, the correct answer is D. This is because the F plasmid carries genes for conjugation, allowing the recipient cell to become F+ (containing the F plasmid). The donor cell remains F. Choice A is incorrect as the outcome can be predicted based on the transfer of the F plasmid. Choice B is incorrect because the donor cell does not become F after transferring the F plasmid. Choice C is incorrect as only the recipient cell becomes F+, not both cells.

Correct Answer: C

Rationale: The correct answer is C: enterotoxigenic E. Coli (ETEC). ETEC adheres to the intestine wall and produces toxins, leading to symptoms like diarrhea. Shigella spp. invade intestinal cells, Salmonella spp. cause inflammation, and Helicobacter pylori infects the stomach lining. This makes them incorrect choices for bacteria adhering to the intestine wall and producing toxins.

Correct Answer: C

Rationale: The correct answer is C because plasmids do not encode essential bacterial properties. They are non-essential, extra-chromosomal DNA molecules that can replicate independently within bacterial cells. Plasmids mainly contain genes for antibiotic resistance, genetic transfer, and other specific functions. Choice A is correct as many plasmids do carry antibiotic resistance genes. Choice B is also accurate as plasmids are indeed smaller, circular, and exist outside the bacterial chromosome. Choice D is true as plasmids can facilitate bacterial conjugation, allowing the transfer of genetic material between bacteria.

Correct Answer: A

Rationale: The correct answer is A: Pseudomonas aeruginosa. This is because Pseudomonas aeruginosa is a common Gram-negative rod that is a non-lactose fermenter and a common cause of severe pneumonia, especially in immunocompromised individuals. It is also known for its resistance to many antibiotics, making it difficult to treat. Summary of other choices: B: Escherichia coli is a lactose fermenter and is not commonly associated with severe pneumonia. C: Klebsiella pneumoniae is a lactose fermenter and is more commonly associated with pneumonia in alcoholics or debilitated patients. D: Enterobacter cloacae is a lactose fermenter and is not a common cause of severe pneumonia.