Following treatment with a highly efficient anti-tuberculosis drug a 48-yearold female developed optic nerve neuritis, memory impairment, cramps. Which of these anti-TB drugs had the patient taken?

Correct Answer: D

Rationale: Step 1: The symptoms of optic nerve neuritis, memory impairment, and cramps are indicative of ethambutol toxicity. Step 2: Ethambutol is known to cause optic nerve toxicity leading to neuritis, as well as CNS toxicity causing memory impairment. Step 3: Ethambutol can also lead to peripheral neuropathy manifesting as cramps. Step 4: Isoniazid is associated with peripheral neuropathy and hepatotoxicity but not with optic nerve neuritis or memory impairment. Step 5: PASA is not commonly used for tuberculosis treatment and does not cause the described symptoms. Step 6: Rifampicin is known for hepatotoxicity and flu-like symptoms, but not specifically for optic nerve neuritis, memory impairment, or cramps. Summary: Ethambutol is the correct answer due to its known side effects of optic nerve toxicity, CNS toxicity, and peripheral neuropathy, which align with the presented symptoms. Ison

Correct Answer: B

Rationale: The correct answer is B because Gram-negative bacteria have an outer membrane with lipopolysaccharides, which is a key characteristic used in Gram staining. This outer membrane is responsible for the pink/red color seen when stained with Gram stain. Choice A is incorrect because Gram-negative bacteria have a thin peptidoglycan layer. Choice C is incorrect because Gram-negative bacteria stain pink, not purple. Choice D is incorrect because all bacteria have a cell wall, but Gram-negative bacteria have a different structure compared to Gram-positive bacteria.

Correct Answer: B

Rationale: The correct answer is B: Cannot induce infectious disease. Saprophytes are microorganisms that obtain nutrients from decaying organic matter and do not cause infectious diseases in humans. They play a vital role in the ecosystem by decomposing dead organisms. Choice A is incorrect because saprophytes do not cause typical infections. Choice C is incorrect because saprophytes do not cause chronic infections. Choice D is incorrect because saprophytes do not cause mixed infections involving multiple pathogens. Therefore, the correct answer is B as saprophytes do not induce infectious diseases.

Correct Answer: A

Rationale: The correct answer is A: Gram-negative stain. Pseudomonas aeruginosa is a gram-negative bacterium, as indicated by the bluish-green pus color. This bacterium has an outer membrane that retains the crystal violet stain, making it appear pink/red after the counterstain with safranin in Gram staining. The other choices are incorrect because Pseudomonas aeruginosa does not typically form spores (B), has a rod-shaped morphology rather than a coccal form (C), and does not exhibit cell pairing (D).

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pneumoniae. This bacterium is a Gram-positive cocci that often appear in pairs and can have a capsule. It is a common cause of sore throat and fever, known as streptococcal pharyngitis. Staphylococcus aureus (B) is a Gram-positive cocci but does not typically form pairs. Neisseria meningitidis (C) is a Gram-negative diplococcus and is more associated with meningitis. Klebsiella pneumoniae (D) is a Gram-negative rod and not typically associated with sore throat and fever.

Correct Answer: B

Rationale: The correct answer is B: Penicillin. Penicillin is the drug of first choice for treating syphilis due to its effectiveness in eradicating the bacterium Treponema pallidum, which causes syphilis. It is the most reliable treatment with well-established efficacy. Gentamicin (A), ciprofloxacin (C), and chloramphenicol (D) are not recommended for treating syphilis as they are not effective against the specific bacteria causing the infection. Penicillin remains the gold standard for syphilis treatment.

Correct Answer: A

Rationale: The correct answer is A: Anthrax. Anthrax is caused by the bacterium Bacillus anthracis, which can form spores that are highly resistant and can survive in the soil for long periods. These spores can remain dormant until they come into contact with a susceptible host, leading to infection. Diphtheria, viral hepatitis, and pertussis are caused by different types of pathogens (bacteria and viruses) that do not have the same ability to persist in soil as anthrax spores. Therefore, the causative agents of these diseases are less likely to exist in the soil for extended periods compared to anthrax spores.

Correct Answer: A

Rationale: The correct answer is A: Clostridium tetani. This bacterium is responsible for causing tetanus due to its production of tetanus toxin. Clostridium perfringens (B) causes gas gangrene, Streptococcus pyogenes (C) causes strep throat and skin infections, and Escherichia coli (D) is a common gut bacteria that can cause food poisoning but not tetanus.

Correct Answer: A

Rationale: The correct answer is A: Clostridium perfringens. Gas gangrene is caused by Clostridium perfringens, a Gram-positive rod bacterium that produces spores. This bacterium is anaerobic and commonly found in soil, where it forms spores that can survive harsh conditions. Clostridium tetani causes tetanus, not gas gangrene. Bacillus anthracis causes anthrax, not gas gangrene. Clostridium botulinum causes botulism, not gas gangrene. Therefore, based on the characteristics of the microorganism described in the question, Clostridium perfringens is the correct identification.