All are non-fermentative gram-negative rods except

Correct Answer: D

Rationale: The correct answer is D, Klebsiella pneumoniae. Klebsiella pneumoniae is a fermentative gram-negative rod, which means it can ferment sugars. In contrast, Pseudomonas aeruginosa, Acinetobacter baumannii, and Stenotrophomonas maltophilia are non-fermentative gram-negative rods. These organisms do not ferment sugars for energy production. Therefore, Klebsiella pneumoniae is the only fermentative organism among the choices, making it the correct answer.

Correct Answer: C

Rationale: The correct answer is C because hemagglutinin of influenza viruses serves as an attachment molecule to the receptor of the target cell, facilitating viral entry. This is crucial for the virus to infect host cells. Choice A is incorrect because hemagglutinin is not part of the viral capsid but rather a surface protein. Choice B is incorrect as hemagglutinin is not directly involved in viral replication, but in host cell attachment. Choice D is incorrect as hemagglutinin is highly antigenic, triggering the host's immune response.

Correct Answer: B

Rationale: Step-by-step rationale: 1. Sodium is the major cation in the intracellular fluid. 2. It plays a crucial role in maintaining cell volume and transmitting nerve impulses. 3. Potassium is the major cation in the extracellular fluid, not intracellular. 4. Bicarbonate and sulfate are anions and not major cations in intracellular fluid. Summary: Choice B (sodium) is correct as it is the major cation in intracellular fluid, essential for various cellular functions. Choices A, C, and D are incorrect as potassium is extracellular, while bicarbonate and sulfate are anions and not predominant cations in intracellular fluid.

Correct Answer: A

Rationale: The correct answer is A: T-lymphocytes. Cell-mediated immunity involves the activation of T-lymphocytes, which play a crucial role in recognizing and killing infected cells. T-lymphocytes include cytotoxic T cells, helper T cells, and regulatory T cells, all of which are involved in different aspects of cell-mediated immunity. Monocytes (choice B) are a type of white blood cell involved in phagocytosis but are not the main mediators of cell-mediated immunity. B-lymphocytes (choice C) are involved in humoral immunity, producing antibodies, not cell-mediated immunity. Choice D (A+B+C) is incorrect because cell-mediated immunity is mainly mediated by T-lymphocytes.

Correct Answer: C

Rationale: The correct answer is C: Leishmaniasis. The description of thin microorganisms with 12-14 uniform tendrils, 10-13 micrometers in length, and pale pink color matches the characteristics of Leishmania parasites seen in Giemsa-stained samples. Leishmania parasites are known to have a distinctive appearance with pointed tips and a specific size range. Syphilis (choice A) is caused by Treponema pallidum, which appears as tightly coiled spirochetes, not tendrils. Trypanosomiasis (choice B) is caused by Trypanosoma parasites, which have a different morphology and staining pattern. Relapsing fever (choice D) is caused by Borrelia recurrentis, which does not match the description given. Therefore, the correct choice is C as the description aligns closely with the characteristic features of Leishmania parasites.

Correct Answer: A

Rationale: The correct answer is A: Peroxidase and catalase. Peroxidase and catalase are enzymes that break down hydrogen peroxide into water and oxygen. Peroxidase helps in breaking down low levels of hydrogen peroxide, while catalase is crucial for breaking down high levels of hydrogen peroxide efficiently. This process is important for organisms to prevent damage from reactive oxygen species. Choices B, C, and D are incorrect: B: Oxygenase and hydroxylase are enzymes involved in different biochemical reactions and do not break down hydrogen peroxide. C: Cytochrome oxidase and cytochrome B5 are involved in electron transport chain reactions and not in breaking down hydrogen peroxide. D: Oxygenase and catalase are not correct as oxygenase is not involved in hydrogen peroxide breakdown, only catalase is.

Correct Answer: D

Rationale: The correct answer is D because enveloped viruses have a lipid bilayer envelope derived from the host cell membrane, which is a complex structure, not exhibiting any specific symmetry. Choice A (cubic symmetry) is incorrect as enveloped viruses do not have any specific geometric shape. Choice B (spiral symmetry) is incorrect as this type of symmetry is typically seen in non-enveloped viruses like helical viruses. Choice C (complex symmetry) is also incorrect as enveloped viruses do not exhibit a specific symmetrical pattern. Therefore, the correct answer is D because enveloped viruses do not have a defined symmetry and can vary in shape and structure.

Correct Answer: A

Rationale: The correct answer is A, Clostridium botulinum. This bacterium produces botulinum toxin, leading to botulism. It is commonly found in soil and improperly canned food. Clostridium tetani causes tetanus, Staphylococcus aureus causes food poisoning, and Salmonella enterica causes salmonellosis. Therefore, A is correct due to its association with botulism, while the other choices are incorrect for causing different diseases.

Correct Answer: A

Rationale: Step 1: Chlorhexidine belongs to the group of biguanides, making choice A accurate. Step 2: It is commonly used for disinfection of hands, skin, and mucous membranes. Step 3: It has a broad spectrum of antimicrobial activity, making it widely applicable. Summary: Choice B is incorrect as chlorhexidine is not classified as an alcohol. Choice C is incorrect as chlorhexidine has various applications. Choice D is incorrect as chlorhexidine is generally safe for use with low toxicity.