Which of the following stains is generally used for the diagnosis of tuberculosis?

Correct Answer: A

Rationale: The correct answer is A: Acid-fast stain. This stain is used for diagnosing tuberculosis due to the unique cell wall composition of Mycobacterium tuberculosis, which resists decolorization by acid-alcohol. This allows the bacteria to retain the primary stain (carbol fuchsin) and appear red under a microscope. Gram stain (B) is not suitable for Mycobacterium tuberculosis as it is gram-positive but does not retain the crystal violet-iodine complex. Negative stain (C) is not used for bacterial identification. Simple stain (D) does not differentiate acid-fast bacteria like Mycobacterium tuberculosis.

Correct Answer: A

Rationale: The correct answer is A: Pseudomonas. Pseudomonas bacteria are known to produce yellow-green pigment and a characteristic odor, specifically in meat-peptone agar. This is due to the production of pyoverdin pigment by Pseudomonas. Other choices like Escherichia, Proteus, Klebsiella, and Azotobacter do not typically produce yellow-green pigment or have a characteristic odor in meat-peptone agar. Therefore, based on the specific characteristics mentioned in the question, Pseudomonas is the most appropriate choice.

Correct Answer: D

Rationale: The correct answer is D: RTECS number. The Registry of Toxic Effects of Chemical Substances (RTECS) number is a unique identifier assigned to chemicals and substances known to cause toxicological effects. It aids in accessing detailed toxicological information such as acute toxicity, carcinogenicity, and mutagenicity. The CAS number (A) is a unique numerical identifier for chemical compounds, not specifically for toxicological information. The atomic number (B) is the number of protons in an element's nucleus, unrelated to toxicology. The DOT ID number (C) is used for hazardous materials transportation, not for toxicological information. Therefore, the RTECS number is the correct choice for finding toxicological information about a specific substance.

Correct Answer: C

Rationale: The correct answer is C: Thermophiles. Thermophiles are bacteria that thrive in high temperatures typically above 45°C. They have specialized enzymes and cellular structures that allow them to survive and even thrive in extreme heat. Psychrophiles (A) are adapted to cold temperatures, mesophiles (B) thrive at moderate temperatures, and halophiles (D) prefer high salt concentrations, making them unsuitable for extreme heat survival. Therefore, Thermophiles are the only bacteria among the choices that are known for their ability to survive in extreme heat.

Correct Answer: A

Rationale: Acyclovir is the correct answer because it is an antiviral drug used to treat herpes simplex and varicella-zoster viruses, not influenza. Tamiflu, Amantadine, and Relenza are used to treat influenza by inhibiting viral replication or easing symptoms. Acyclovir's mechanism of action targets different viruses, making it ineffective for treating influenza.

Correct Answer: C

Rationale: The correct answer is C (100°C) because the Koch apparatus is used for sterilization, and the standard temperature for sterilization is 100°C. At this temperature, most microorganisms are killed, making it an effective method for sterilization. Choice A (90°C), B (95°C), and D (110°C) are incorrect because they are not commonly used temperatures for sterilization purposes. Choosing a temperature lower than 100°C may not effectively kill all microorganisms, while choosing a temperature higher than 100°C may lead to unnecessary energy consumption without providing additional sterilization benefits.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pyogenes. This is because Streptococcus pyogenes is a Gram-positive cocci in chains bacterium that is catalase-negative, making it the most likely causative agent in this scenario. Streptococcus pyogenes is a common pathogen causing bacterial endocarditis. Summary of other choices: B: Staphylococcus aureus is a Gram-positive cocci bacterium but is catalase-positive, so it is unlikely in this case. C: Enterococcus faecalis is a Gram-positive cocci bacterium, but it is catalase-negative, which is not consistent with the given information. D: Micrococcus luteus is a Gram-positive cocci bacterium but is catalase-positive, making it an unlikely causative agent.

Correct Answer: B

Rationale: The correct answer is B: Ethambutol. Ethambutol is known to cause optic neuritis, affecting the visual nerve. It is a well-documented side effect of this drug. Isoniazid (Choice A) is associated with peripheral neuropathy, not optic neuritis. Kanamycin (Choice C) is known for its side effects on the inner ear, causing hearing loss. Rifampicin (Choice D) is not typically associated with optic neuritis but can cause other adverse effects like hepatitis. By process of elimination and knowledge of drug side effects, Ethambutol is the most likely culprit.

Correct Answer: A

Rationale: The correct answer is A because spheroplasts are bacteria with defective cell walls that have a parietal layer (peptidoglycan layer) and a defective peptidoglycan layer. This is because spheroplasts have lost their rigid cell wall structure, leading to an incomplete peptidoglycan layer. Choice B is incorrect as the cytoplasmic membrane is not directly affected by the loss of cell wall integrity. Choice C is incorrect because spheroplasts do not have an outer membrane defect, but rather a defect in the peptidoglycan layer. Choice D is incorrect because spheroplasts still have peptidoglycan, even though it is defective.