Mycobacterium tuberculosis is

Correct Answer: D

Rationale: The correct answer is D because Mycobacterium tuberculosis is a straight or slightly curved rod with occasional polymorphism. This bacterium does not conform to the characteristics of gram-negative coccus (A), gram-positive coccus (B), or gram-negative rod (C). Mycobacterium tuberculosis is characterized by its unique cell wall composition, which includes high lipid content and mycolic acids, contributing to its acid-fast staining property. The other choices are incorrect because they do not accurately describe the morphology of Mycobacterium tuberculosis.

Correct Answer: B

Rationale: The correct answer is B: slime mold. Plasmodium is a type of slime mold, specifically a parasitic protist that causes malaria in humans. Slime molds are a group of organisms that share characteristics of both fungi and protozoa. Plasmodium does not belong to the other categories listed: A) protozoan refers to a broad category of single-celled eukaryotic organisms, C) spirochetes are a type of bacteria, and D) helminths are parasitic worms. Therefore, the correct classification for Plasmodium is slime mold.

Correct Answer: A

Rationale: The most likely diagnosis is Actinomycosis. This is because the patient's presentation of a painful swelling with a fistula containing white granules and yellow-green honeycomb-like tissue is classic for Actinomycosis. Actinomyces is a gram-positive anaerobic bacterium that forms sulfur granules in tissues. Tuberculosis (B) typically presents with caseating granulomas, not sulfur granules. Leprosy (C) presents with skin lesions and nerve damage, not characteristic of this case. Syphilis (D) usually presents with painless ulcers and rash, not the painful swelling and fistula seen in this patient.

Correct Answer: C

Rationale: The bacterial capsule is composed of polysaccharides. This outer layer helps bacteria evade the host immune system, protect against desiccation, and aid in attachment to host cells. Polysaccharides are long chains of sugar molecules, providing a protective barrier for the bacteria. Lipopolysaccharides (choice A) are found in the outer membrane of Gram-negative bacteria and are not a major component of the capsule. Teichoic acid (choice B) is a component of the cell wall in Gram-positive bacteria, not the capsule. Peptidoglycan (choice D) is another component of the cell wall but is not part of the capsule.

Correct Answer: D

Rationale: The correct answer is D because all three bacteria - Salmonella enterica, Clostridium botulinum, and Escherichia coli - are commonly associated with foodborne illnesses. Salmonella causes gastroenteritis, Clostridium botulinum causes botulism, and E. coli can lead to severe food poisoning. Each bacterium has different mechanisms of causing illness, but all can be transmitted through contaminated food. Choices A, B, and C alone are incorrect because they do not encompass the full spectrum of bacteria commonly linked to foodborne illnesses.

Correct Answer: D

Rationale: The correct answer is D, chromoblastomycosis. This is a chronic localized subcutaneous infection caused by certain fungi, resulting in verrucoid lesions on the skin. The other choices are incorrect because: A: Candidiasis is a superficial fungal infection, not characterized by verrucoid lesions. B: Leprosy is a systemic bacterial infection, not localized to the skin with verrucoid lesions. C: Shingles is caused by the varicella-zoster virus, presenting as a painful rash with blisters, not verrucoid lesions.

Correct Answer: C

Rationale: The correct answer is C: All answers are correct. Pneumonia can be caused by various pathogens, including Legionella pneumophila and Mycoplasma pneumoniae. Choice C is correct because both A and B are known causative agents of pneumonia. Choice D is incorrect because we know that Legionella pneumophila and Mycoplasma pneumoniae can cause pneumonia, so the statement "None of the above" is not accurate in this context.

Correct Answer: A

Rationale: The most probable diagnosis is Tetanus (Choice A) based on the symptoms described. Tetanus is characterized by muscle stiffness, difficulty opening the mouth (trismus), muscle spasms, and convulsions. The progression of symptoms from muscle tension to generalized convulsions every 10-15 min is classic for tetanus. Tetania (Choice B) is similar but typically presents with more subtle muscle contractions rather than convulsions. Meningoencephalitis (Choice C) presents with fever, headache, and altered mental status, not the muscle symptoms described. Hemorrhagic stroke (Choice D) presents with sudden onset neurological deficits like weakness or sensory changes, not the muscle symptoms described.

Correct Answer: D

Rationale: The correct answer is D (All of the above). All three bacteria (Escherichia coli, Salmonella enterica, Pseudomonas aeruginosa) produce endotoxins that can lead to septic shock. Endotoxins are part of the outer membrane of Gram-negative bacteria and can trigger a strong immune response, leading to septic shock when released in large amounts. Escherichia coli and Salmonella enterica are common causes of bacterial septic shock, while Pseudomonas aeruginosa is known for its ability to produce endotoxins that contribute to severe infections and septic shock. Therefore, all three choices are correct in this context.