A family has two children. The younger child is under the year. The child has developed spastic cough attacks. Similar clinical presentation was observed in the elder preschool child one month ago. The doctor suspects pertussis infection. What method enables retrospective diagnostics of this disease?

Correct Answer: A

Rationale: The correct answer is A: Serological. Serological testing involves analyzing blood samples for specific antibodies produced in response to the pertussis infection. This method can detect past infections by identifying the presence of antibodies against the pertussis bacteria in the blood. In this case, since the doctor suspects pertussis infection in both children, serological testing can confirm if they have been exposed to the bacteria. Summary: B: Biological testing does not specifically target pertussis antibodies in the blood. C: Bacteriological testing involves culturing bacteria from samples, which may not be as sensitive for retrospective diagnosis. D: Molecular biological testing focuses on genetic material of the bacteria, which may not provide direct evidence of past infection.

Correct Answer: C

Rationale: The correct answer is C: Cell wall. Penicillin targets the cell wall of bacteria by inhibiting the formation of peptidoglycan, a crucial component of the cell wall. This weakens the cell wall, leading to bacterial cell lysis. Choice A (DNA) is incorrect because penicillin does not directly target DNA. Choice B (Plasma membrane) is incorrect as penicillin primarily affects the cell wall, not the plasma membrane. Choice D (Ribosomes) is incorrect because penicillin does not target bacterial ribosomes, which are involved in protein synthesis.

Correct Answer: A

Rationale: The correct answer is A: Clostridium botulinum. This bacterium produces the botulinum neurotoxin, which causes paralysis by blocking the release of acetylcholine at neuromuscular junctions. Clostridium perfringens causes gas gangrene, not paralysis. Escherichia coli is associated with gastrointestinal infections, not paralysis. Staphylococcus aureus produces enterotoxins causing food poisoning, not paralysis. Therefore, Clostridium botulinum is the correct choice based on its well-known association with paralysis due to botulinum neurotoxin production.

Correct Answer: B

Rationale: The correct answer is B: Treponema pallidum. The scenario describes symptoms of primary syphilis, which is caused by Treponema pallidum. The presence of a painless ulcer (chancre) and enlarged inguinal lymph nodes are characteristic of syphilis. Dark field microscopic examination showing motile, curved spirochetes is highly specific for Treponema pallidum. Incorrect explanations: A: Chlamydia trachomatis typically causes urethritis or cervicitis, not painless ulcers. C: Neisseria gonorrhoeae causes gonorrhea, which presents with purulent discharge, not painless ulcers. D: Herpes simplex virus type 2 causes genital herpes, leading to painful ulcers and vesicles, not painless ulcers seen in syphilis.

Correct Answer: A

Rationale: The correct answer is A: Mantoux test. The Mantoux test is used to detect tuberculosis infection by injecting a small amount of tuberculin under the skin and checking for a reaction. This test helps identify individuals who have been exposed to tuberculosis. The other choices are incorrect because: B: Schick test is used to determine immunity to diphtheria, not tuberculosis. C: Anthraxine test is used for anthrax, not tuberculosis. D: Burnet test is not a recognized medical test for tuberculosis.

Correct Answer: D

Rationale: The correct answer is D because all the options are essential for a PCR reaction. A: DNA segment is required as the template for amplification. B: Two oligonucleotide primers are needed to initiate DNA replication. C: Heat stable DNA polymerase (not just heat stable DNA) is crucial for withstanding the high temperatures during PCR. In summary, without any of these components, the PCR reaction cannot proceed effectively.

Correct Answer: D

Rationale: The correct answer is D: All of the above. Hepatitis B infection can present with jaundice due to liver inflammation, elevated serum aminotransferase levels due to liver damage, and sometimes no symptoms in the acute phase. This comprehensive presentation covers the spectrum of possible clinical manifestations of hepatitis B infection. Choices A and B are correct as they are common manifestations of hepatitis B infection. Choice C is incorrect as hepatitis B infection can indeed present with symptoms, making option D the most appropriate choice.

Correct Answer: A

Rationale: The correct answer is A because growth factors are essential nutrients that bacteria cannot synthesize on their own and must obtain from the environment for their growth. Bacteria rely on these external factors for processes like cell division, metabolism, and survival. Choice B is incorrect because bacteria can only synthesize growth factors in limited amounts, not sufficient for their growth. Choice C is incorrect as bacterial cells do not store growth factors in granules. Choice D is incorrect because bacterial cells do not synthesize growth factors in large amounts.

Correct Answer: D

Rationale: The correct answer is D: Immunocomplex. In this case, the patient's symptoms of fever, joint pains, rash, and itch along with leukopenia and thrombocytopenia indicate a serum sickness reaction. This is a type III hypersensitivity reaction where antigen-antibody complexes deposit in tissues, leading to inflammation and tissue damage. The symptoms typically occur 1-2 weeks after exposure to the antigen. Anaphylactic reaction (choice A) is immediate and involves IgE antibodies. Cytotoxic reaction (choice B) involves destruction of cells by antibodies. Delayed hypersensitivity (choice C) usually takes 48-72 hours to develop and involves T-cells. Therefore, the correct answer is D as it aligns with the symptoms and timeline of a type III hypersensitivity reaction.