Which of the following has a contact route of transmission

Correct Answer: D

Rationale: The correct answer is D: HIV. HIV is transmitted through direct contact with certain body fluids such as blood, semen, vaginal fluids, and breast milk. This direct contact route of transmission makes it different from the other choices. Salmonellosis is typically transmitted through contaminated food or water (not direct contact). Tularemia is usually transmitted through insect bites or contact with infected animals. Rubella is primarily transmitted through respiratory droplets. Therefore, HIV is the only option with a contact route of transmission.

Correct Answer: D

Rationale: The correct answer is D, "All of the above," because all three bacteria (Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus) can cause urinary tract infections. E. coli is the most common causative agent of UTIs, followed by Staphylococcus aureus and occasionally Pseudomonas aeruginosa. Each of these bacteria has different virulence factors that enable them to infect the urinary tract. Therefore, it is important to consider all three options when diagnosing and treating UTIs. Choices A, B, and C are incorrect because each of those bacteria can individually cause UTIs, so the correct answer is D, as it encompasses all the possible causative agents.

Correct Answer: B

Rationale: The correct answer is B: Clostridium botulinum. This bacterium produces the botulinum toxin, which causes botulism by blocking nerve functions. Clostridium tetani causes tetanus, not botulism. Staphylococcus aureus produces toxins that cause food poisoning, not botulism. Bacillus anthracis causes anthrax, not botulism. Therefore, the correct choice is Clostridium botulinum because it is the specific bacterium responsible for producing the toxin that leads to botulism.

Correct Answer: C

Rationale: To calculate the total magnification, we multiply the magnification of the ocular lens by the magnification of the objective lens. In this case, 10 (ocular) x 40 (objective) = 400. This is why choice C (400) is correct. Choices A, B, and D are incorrect because they do not represent the correct calculation of total magnification based on the given magnification powers of the ocular and objective lenses.

Correct Answer: B

Rationale: The correct answer is B: Spirochete. Lyme disease is caused by the bacterium Borrelia burgdorferi, which is a spirochete. Spirochetes are spiral-shaped bacteria that move by rotating like a corkscrew, which is characteristic of Borrelia burgdorferi. A: Spirillum - Spirillum bacteria are helical-shaped but are not the causative agent for Lyme disease. C: Vibrio - Vibrio bacteria are curved or comma-shaped and are not associated with Lyme disease. D: Diplococcus - Diplococcus bacteria are spherical-shaped and typically occur in pairs, not the causative agent for Lyme disease. Therefore, the correct answer is B because Borrelia burgdorferi is a spirochete bacterium that causes Lyme disease.

Correct Answer: D

Rationale: The correct answer is D because all three bacteria listed can produce toxins that cause severe diarrhea. Clostridium difficile produces toxins that can lead to antibiotic-associated diarrhea, Vibrio cholerae produces a toxin that causes cholera, and certain strains of Escherichia coli produce toxins that result in severe diarrhea. Therefore, choosing option D is correct because all the mentioned bacteria can cause severe diarrhea. Options A, B, and C are incorrect individually because each bacterium listed can produce a toxin resulting in severe diarrhea.

Correct Answer: A

Rationale: The correct answer is A: Icosahedral structures. Icosahedral symmetry is commonly found in viruses due to its efficient way of packing genetic material. The icosahedron has 20 equilateral triangular faces, making it ideal for viral capsids. The other choices, B: Hexahedral, C: Tetrahedral, and D: Dodecahedral structures, do not accurately describe the cubic type of symmetry seen in viruses. Hexahedral refers to a six-faced polyhedron, tetrahedral to a four-faced polyhedron, and dodecahedral to a twelve-faced polyhedron, none of which align with the structure commonly observed in viruses.

Correct Answer: A

Rationale: The correct answer is A: chloroplasts. Algae and plant cells have chloroplasts, which are responsible for photosynthesis. This organelle contains chlorophyll, enabling these cells to convert sunlight into energy. Mitochondria (B) are found in all eukaryotic cells, not specific to algae and plants. Vacuoles (C) are present in plant cells but also in other eukaryotic cells. Vesicles (D) are membrane-bound sacs found in all types of cells for transport and storage purposes, not unique to algae and plants. Therefore, A is the correct answer.

Correct Answer: A

Rationale: The correct answer is A: Clostridium botulinum. This bacterium produces the neurotoxin responsible for botulism. It thrives in anaerobic environments like improperly canned foods. Clostridium difficile (B) causes colitis, not botulism. Staphylococcus aureus (C) causes food poisoning but not botulism. Escherichia coli (D) can cause gastrointestinal illness but not botulism.