A 10-year-old child had the mantoux tuberculin test administered. 48 hours later a papule up to 8 mm in diameter appeared on the site of the injection. What type of hypersensitivity reaction developed after the tuberculin injection?

Correct Answer: A

Rationale: The correct answer is A: Type IV hypersensitivity reaction. This type of reaction is characterized by a delayed response involving T cells. In this case, the appearance of a papule after 48 hours indicates a delayed hypersensitivity reaction, which is typical of a Type IV reaction. The other choices are incorrect because: B: Arthus phenomenon is a localized immune complex-mediated reaction, not seen in tuberculin tests. C: Seroreaction typically involves antibodies reacting with soluble antigens, not seen in this scenario. D: Type II hypersensitivity reactions involve antibodies targeting specific cells or tissues, which is not the mechanism at play in this case.

Correct Answer: A

Rationale: The correct answer is A: Teratogenesis. Teratogenesis refers to the process of abnormal development of the fetus leading to congenital defects due to exposure to harmful agents during pregnancy. In this case, toxoplasmosis infection during pregnancy can lead to teratogenesis, causing multiple congenital defects in the child. Other choices are incorrect because B: Cancerogenesis refers to the process of cancer formation, C: Recombination is a genetic process unrelated to congenital defects, and D: Chemical mutagenesis refers to mutations caused by chemical agents, not necessarily congenital defects.

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: Multiplies by binary fission. Bacterial cells reproduce through binary fission, where a single cell divides into two identical daughter cells. This process is essential for bacterial growth and multiplication. A: The oxidative phosphorylation does not take place in the mitochondria of bacterial cells but in the cell membrane. B: Capsules are not organelles but outer protective layers found in some bacterial cells. C: Bacterial cells contain both DNA and RNA, essential for their genetic information and protein synthesis.

Correct Answer: D

Rationale: The correct answer is D: metronidazole. Metronidazole is specifically effective against protozoan infections due to its ability to target and disrupt the DNA of the parasites. It is commonly used to treat infections such as trichomoniasis and giardiasis that affect the reproductive system. Ampicillin (A) and tetracycline (B) are antibiotics that target bacteria, not protozoa. Ciprofloxacin (C) is also an antibiotic that is effective against certain bacterial infections but not protozoan infections. Therefore, metronidazole is the most appropriate choice for fighting protozoan infections of the reproductive system.

Correct Answer: C

Rationale: Step 1: S. aureus is known to produce hemolysins, leucocidins, and enterotoxin. Step 2: S. aureus colonies usually exhibit golden-yellow pigmentation with beta-hemolytic zones. Step 3: S. aureus has developed resistance to penicillin due to the production of beta-lactamase. Step 4: Therefore, statement C is not true as S. aureus is not always sensitive to penicillin. Summary: Choices A and B are correct statements about S. aureus, while choice C is incorrect due to the increasing penicillin resistance seen in S. aureus.

Correct Answer: A

Rationale: Step-by-step rationale: 1. Arenaviridae family includes viruses with a segmented genome. 2. Lassa virus has a segmented genome, placing it in the Arenaviridae family. 3. Crimean-Congo hemorrhagic fever virus belongs to the Nairoviridae family, not Arenaviridae. 4. Rabies virus belongs to the Rhabdoviridae family, not Arenaviridae. 5. Epstein-Barr virus belongs to the Herpesviridae family, not Arenaviridae. Summary: A: Lassa virus is correct because it has a segmented genome, characteristic of Arenaviridae. B, C, D: Crimean-Congo hemorrhagic fever virus, Rabies virus, and Epstein-Barr virus belong to different virus families, not Arenaviridae.

Correct Answer: C

Rationale: The correct answer is C: fungi. Both penicillin and cephalosporin are produced by certain species of fungi. Penicillin is derived from the Penicillium fungi, while cephalosporin is produced by Cephalosporium fungi. Fungi have the ability to synthesize these antibiotics as part of their defense mechanisms against other microorganisms. Algae (A), slime molds (B), and protozoans (D) do not have the capability to produce antibiotics like penicillin and cephalosporin. Algae are mainly photosynthetic organisms, slime molds are protists that lack the ability to synthesize complex antibiotics, and protozoans are single-celled eukaryotic organisms that do not produce antibiotics like fungi do.

Correct Answer: A

Rationale: The correct answer is A: Helicobacter. Helicobacter pylori is the main causative agent of peptic ulcer disease and is characterized by its gram-negative arcuate bent shape and positive urease activity. Helicobacter pylori specifically colonizes the stomach mucosa and is associated with various gastrointestinal disorders. Spirochetes (choice B), spirilla (choice C), and Leptospira (choice D) are not typically associated with peptic ulcer disease or stomach mucosa infections, making them incorrect choices in this context.