ATI RN
foundations in microbiology test bank Questions
Question 1 of 5
In which of the following GIT infections, the bacteria adhere to the intestine wall and produce toxins
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.
Question 2 of 5
The organisms to be identified have a nucleus surrounded by a nuclear membrane. Genetic material is concentrated predominantly in the chromosomes which consist of DNA strands and protein molecules. These cells divide mitotically. Identify these organisms:
Correct Answer: A
Rationale: Step-by-step rationale: 1. The presence of a nucleus with a nuclear membrane indicates eukaryotic cells. 2. Eukaryotes have genetic material in chromosomes made of DNA and proteins. 3. Mitotic division is characteristic of eukaryotic cells. 4. Therefore, the organisms described are eukaryotes. Summary: - Bacteriophages (B) are viruses that infect bacteria. - Prokaryotes (C) lack a nucleus and their genetic material is not organized into chromosomes. - Viruses (D) are not considered living organisms and do not have a nucleus or chromosomes.
Question 3 of 5
Examination of a smear from a chancre revealed mobile, long, spiral microorganisms with 8-12 regular coils. What is the causative agent?
Correct Answer: A
Rationale: The correct answer is A: Treponema. The characteristics described match Treponema pallidum, the causative agent of syphilis. Treponema has long, spiral shape with 8-12 regular coils. Leptospira (B) is a spirochete but has fewer coils and causes leptospirosis. Borrelia (C) is another spirochete but typically has irregular coils and causes Lyme disease. Vibrios (D) are curved rods and not spirochetes.
Question 4 of 5
Gram-negative bacteria have a cell wall that:
Correct Answer: C
Rationale: The correct answer is C, as Gram-negative bacteria have a cell wall containing lipopolysaccharides. This outer membrane structure is unique to Gram-negative bacteria and plays a critical role in pathogenicity and immune response. Teichoic acid (choice A) is found in Gram-positive bacteria. The cell wall of Gram-negative bacteria is thinner than that of Gram-positive bacteria (choice B). The cell wall of Gram-negative bacteria is not composed entirely of peptidoglycan (choice D), as it also contains other components like lipopolysaccharides.
Question 5 of 5
Microscopic examination of a smear from a chancre revealed spiral microorganisms. The bacteria were thin and mobile with 8-12 regular coils. What is the likely diagnosis?
Correct Answer: A
Rationale: The correct diagnosis is A: Syphilis. The spiral microorganisms described are characteristic of Treponema pallidum, the causative agent of syphilis. The thin and mobile bacteria with 8-12 regular coils match the morphology of Treponema pallidum. Leptospirosis is caused by Leptospira interrogans, which are thicker and have hook-like ends, different from the described bacteria. Lyme disease is caused by Borrelia burgdorferi, which has a different appearance than the thin, coiled bacteria in the smear. Relapsing fever is caused by Borrelia recurrentis, which typically have irregular coils, unlike the regular coils seen in the smear.