The compact structure in which the genome of the bacteria is located is called:

Correct Answer: A

Rationale: The correct answer is A: Nucleoid. The bacterial genome is located in the nucleoid, a region within the bacterial cell where the genetic material is condensed and organized. This structure is not the same as a nucleus found in eukaryotic cells. The other choices (B: Nucleotide and C: ATP) are incorrect because nucleotide refers to a building block of DNA or RNA, and ATP is a molecule used for energy transfer in cells, neither of which specifically houses the bacterial genome. Choice D: None of the above is incorrect as well, as the correct term for the compact structure containing the bacterial genome is the nucleoid.

Correct Answer: C

Rationale: Nigrosin is used in negative staining, where the background is stained instead of the cells themselves. This technique helps highlight the morphology and structure of cells that may be damaged by traditional staining methods. Nigrosin is negatively charged and repels the negatively charged bacterial cells, resulting in a clear halo around the cells. This process is particularly useful for observing capsules and determining cell size and shape. The other options are incorrect because simple staining uses a single dye to color the entire cell, gram staining involves a series of dyes to differentiate between gram-positive and gram-negative bacteria, and acid-fast staining is used to detect acid-fast organisms like Mycobacterium.

Correct Answer: A

Rationale: The correct answer is A: Gram-positive rod-shaped bacterium. Campylobacter fetus is actually a Gram-negative bacterium. This is because it has a thin peptidoglycan layer in its cell wall, which does not retain the crystal violet stain used in the Gram-staining technique. It appears red or pink under a microscope after counterstaining with safranin. Therefore, statement A is incorrect. B: Optimal temperature for cultivation 35-37C - Correct, as Campylobacter fetus thrives at this temperature range. C: Opportunistic pathogen causes infections usually in newborns, immunocompromised patients, and cancer - Correct, as Campylobacter fetus can cause infections in these populations. D: Fastidious, microaerophile - Correct, as Campylobacter fetus is fastidious and requires specific growth conditions, including low oxygen levels.

Correct Answer: D

Rationale: The correct answer is D: Clindamycin. Clindamycin is a lincosamide antibiotic that is safe to use in patients with a history of anaphylaxis to beta-lactam antibiotics like cefaclor. Clindamycin is effective against streptococcus pyogenes and is a suitable alternative in this case. Amoxicillin (choice A) is a beta-lactam antibiotic similar to cefaclor and may cause a cross-reactive allergic reaction. Meropenem (choice B) is a carbapenem antibiotic and not typically used for acute pharyngitis. Cephalexin (choice C) is a cephalosporin antibiotic and may also cause cross-reactivity in patients with a history of anaphylaxis to cefaclor.

Correct Answer: B

Rationale: The correct answer is B: Bordetella pertussis. This bacterium causes whooping cough by infecting the respiratory tract. It produces toxins that lead to severe coughing fits characteristic of the disease. Clostridium botulinum (A) causes botulism, Streptococcus pneumoniae (C) causes pneumonia, and Neisseria meningitidis (D) causes meningitis, not whooping cough. B. pertussis is the only bacterium specifically associated with whooping cough.

Correct Answer: A

Rationale: The correct answer is A: Binding of IgE fixed to the mast cells. The Bezredka method involves injecting small, gradually increasing doses of the antigen (tetanus toxoid) to desensitize the body and prevent anaphylactic shock. This process works by binding the IgE antibodies fixed to mast cells, thereby reducing the release of allergic mediators like histamine. This prevents the cascade of events that lead to anaphylactic shock. Choice B (Blocking the mediator synthesis in the mast cells) is incorrect because the Bezredka method does not block mediator synthesis but rather prevents the release of mediators by binding IgE. Choice C (Stimulation of immune tolerance to the antigen) is incorrect as the Bezredka method does not primarily focus on inducing immune tolerance but rather on preventing anaphylactic reactions. Choice D (Stimulation of the synthesis of antigen-specific IgG) is incorrect because the Bezredka method targets IgE antibodies on mast cells

Correct Answer: A

Rationale: The correct answer is A: Toxoplasmosis. Toxoplasmosis is caused by the protozoan Toxoplasma gondii, which can be transmitted from mother to fetus during pregnancy leading to stillbirth and malformations. This parasite can cross the placenta and infect the fetus, causing severe complications. Leishmaniasis (B), Malaria (C), and Amebiasis (D) are not known to cause intrauterine death or malformations in the same way as Toxoplasmosis. Leishmaniasis is transmitted by sandflies, Malaria by mosquitoes, and Amebiasis by contaminated food or water.

Correct Answer: C

Rationale: The correct answer is C: plasmids. Plasmids are nonchromosomal DNA molecules commonly found in bacterial cells, providing additional genetic material for bacteria. They are not essential for bacterial survival but can confer advantages such as antibiotic resistance. Endospores (A) are dormant bacterial structures resistant to harsh conditions. Transposons (B) are mobile genetic elements that can move within a genome. Prions (D) are misfolded proteins causing neurodegenerative diseases, not DNA molecules.

Correct Answer: C

Rationale: The correct answer is C: Fecal enterococcus. In a drugstore setting, finding a fecal-indicative microorganism like fecal enterococcus indicates a potential contamination from fecal matter, which poses a significant health risk. Staphylococcus aureus (Choice A) and α-haemolytic streptococcus (Choice D) are not typically indicative of fecal contamination. Colon bacillus (Choice B) is a common bacterium found in the gut but is not specifically indicative of fecal contamination. Therefore, choice C, fecal enterococcus, is the most appropriate microorganism indicating unsanitary conditions in a drugstore.