A 10 year old child was subjected to Mantoux test (with tuberculin). 48 hours later a papule up to 8 mm in diameter appeared on the site of tuberculin injection. What type of hyperesponsiveness reaction has developed after tuberculin injection?

Correct Answer: A

Rationale: The correct answer is A: Hyperresponsiveness reaction type IV. This type of reaction, also known as delayed-type hypersensitivity, is characterized by the activation of T lymphocytes and macrophages, leading to inflammation at the site of antigen exposure. In the case of the Mantoux test, the appearance of a papule 48 hours later indicates a delayed hypersensitivity reaction mediated by T cells. Choice B: Reaction of Arthus phenomenon type is incorrect as this type of reaction involves immune complexes forming in the blood vessels leading to tissue damage, which is not the mechanism seen in the Mantoux test reaction. Choice C: Reaction of serum sickness type is incorrect as this type of reaction involves the formation of immune complexes in the blood leading to systemic symptoms like fever, rash, and joint pain, which is not typically seen in the Mantoux test reaction. Choice D: Atopic reaction is incorrect as atopic reactions involve IgE antibodies and mast cell degranulation, which are not the mechanisms

Correct Answer: A

Rationale: Step 1: Streptococcus mutans is known for its ability to produce acids that contribute to the demineralization of tooth enamel, leading to dental caries. Step 2: Streptococcus pneumoniae is a common cause of respiratory infections, not dental caries. Step 3: Bacillus anthracis causes anthrax, a serious bacterial infection, not dental caries. Step 4: Clostridium botulinum causes botulism, a severe form of food poisoning, not dental caries. Summary: Streptococcus mutans is the correct answer as it is specifically associated with causing dental caries, while the other choices are linked to different diseases.

Correct Answer: C

Rationale: The correct answer is C: Method of Moller. This method uses malachite green to stain bacterial spores due to their resistance to decolorization. The other choices, A, B, and D, are incorrect because Romanovski-Gymsa is used for staining blood smears, Ziehl-Nielsen is used for acid-fast bacteria, and Neisser is used for staining Neisseria species, not bacterial spores.

Correct Answer: D

Rationale: The correct answer is D, "All of the above." Clostridium botulinum causes botulism, Salmonella enterica causes salmonellosis, and Escherichia coli can cause foodborne illnesses such as E. coli infection. All three bacteria are associated with foodborne illnesses due to contamination of food or water sources. Therefore, selecting "All of the above" is the most appropriate choice as it includes all the bacteria commonly linked to foodborne illnesses. The other choices (A, B, and C) are incorrect because they do not encompass all the bacteria associated with foodborne illnesses as stated above.

Correct Answer: C

Rationale: The correct answer is C: Hepatitis A virus. This is because Hepatitis A virus is a non-enveloped virus, while choices A, B, and D are all enveloped viruses. Enveloped viruses have a lipid bilayer membrane surrounding their protein capsid, aiding in their ability to infect host cells. Hepatitis C, B, and D viruses all possess this lipid envelope, making them enveloped viruses. Hepatitis A virus, on the other hand, lacks this lipid envelope and is classified as a non-enveloped virus. Therefore, the correct answer is C.

Correct Answer: A

Rationale: The correct diagnosis is Leptospirosis. Leptospirosis presents with headache, fever, muscle pain, jaundice, and kidney involvement. The patient's symptoms of headache, lumbar and muscle pain, high fever, icteric scleras, and dark urine are classic for Leptospirosis. The enlarged liver could be due to liver involvement in the disease. The absence of splenic enlargement and normal stool color rule out malaria. Infectious mononucleosis typically presents with sore throat and lymphadenopathy, which are absent in this case. Viral hepatitis A may present with similar symptoms, but the presence of muscle pain and dark urine is more indicative of Leptospirosis. Therefore, based on the patient's symptoms and clinical findings, Leptospirosis is the most likely diagnosis.

Correct Answer: C

Rationale: Rationale: 1. Vibrio cholerae produces cholera toxin causing severe diarrhea. 2. Clostridium tetani causes tetanus, not diarrhea. 3. Clostridium botulinum causes botulism, not diarrhea. 4. Shigella dysenteriae causes dysentery, not typical diarrhea. Summary: A: Incorrect, causes tetanus. B: Incorrect, causes botulism. C: Correct, produces cholera toxin causing severe diarrhea. D: Incorrect, causes dysentery.

Correct Answer: B

Rationale: The correct answer is B: H antigen. Flagellar antigen is typically referred to as the H antigen in bacteria. Flagella are the whip-like structures used for movement in bacteria, and the H antigen is specifically associated with the flagella. The other choices (A: D antigen, C: K antigen, D: F antigen) are not related to flagella in bacteria and are commonly associated with other types of antigens in bacterial classification.

Correct Answer: A

Rationale: The correct answer is A: Hyperresponsiveness reaction type IV. This type of reaction, also known as delayed-type hypersensitivity, is characterized by the activation of T lymphocytes and macrophages, leading to inflammation at the site of antigen exposure. In the case of the Mantoux test, the appearance of a papule 48 hours later indicates a delayed hypersensitivity reaction mediated by T cells. Choice B: Reaction of Arthus phenomenon type is incorrect as this type of reaction involves immune complexes forming in the blood vessels leading to tissue damage, which is not the mechanism seen in the Mantoux test reaction. Choice C: Reaction of serum sickness type is incorrect as this type of reaction involves the formation of immune complexes in the blood leading to systemic symptoms like fever, rash, and joint pain, which is not typically seen in the Mantoux test reaction. Choice D: Atopic reaction is incorrect as atopic reactions involve IgE antibodies and mast cell degranulation, which are not the mechanisms