The Baltimore classification system places viruses into __________ groups.

Correct Answer: C

Rationale: The Baltimore classification system categorizes viruses based on their genome type and replication strategy. It divides viruses into seven groups: Group I (dsDNA), Group II (ssDNA), Group III (dsRNA), Group IV (ssRNA(+)), Group V (ssRNA(-)), Group VI (ssRNA-RT), and Group VII (dsDNA-RT). Each group represents a distinct viral genome and replication method. Therefore, the correct answer is C. The other choices are incorrect because the Baltimore classification system specifically identifies viruses into seven groups, not four, five, or nine.

Correct Answer: B

Rationale: The correct answer is B: Salmonella enterica. Typhoid fever is caused by the bacterium Salmonella enterica serotype Typhi. This specific strain of Salmonella is responsible for typhoid fever, a serious illness characterized by high fever, abdominal pain, and diarrhea. Escherichia coli (choice A) is not the causative agent of typhoid fever. Shigella flexneri (choice C) causes bacillary dysentery, not typhoid fever. Staphylococcus aureus (choice D) can cause food poisoning but is not associated with typhoid fever.

Correct Answer: B

Rationale: The correct answer is B: resisting phagocytosis. Bacterial capsules are composed of polysaccharides that help bacteria evade phagocytosis by immune cells. This physical barrier prevents immune cells from engulfing and destroying the bacteria. Facilitating motility (A), synthesizing DNA (C), and producing energy (D) are not primary functions of bacterial capsules. Motility is usually facilitated by flagella, DNA synthesis occurs in the bacterial chromosome, and energy production is typically carried out by metabolic processes within the bacterial cell.

Correct Answer: B

Rationale: The correct answer is B: Before antibiotic therapy is begun. Detecting penicillin-resistant, beta-lactamase-producing strains before antibiotic therapy is crucial to ensure proper treatment. If detected after therapy (choice A), it may lead to treatment failure. Detection during therapy (choice C) may result in delayed or ineffective treatment. Choice D is incorrect as early detection is essential for successful management.

Correct Answer: B

Rationale: The correct answer is B because viruses can indeed be cultured on hen embryos, cell cultures, and experimental animals in vitro. This method allows for the replication and study of viruses outside the host organism. Option A is incorrect as viral cultivation is possible in laboratory settings. Option C is incorrect because while viruses can be grown on nutrient media, it is not the only method. Option D is incorrect as viruses can be cultured in various types of cell cultures, not just human embryonic ones.

Correct Answer: A

Rationale: The correct answer is A: general-purpose hoods. Bypass fume hoods are designed to handle a wide range of chemical fumes and vapors, making them suitable for various types of experiments and processes. They are not specifically designed for radioisotopes (B), perchloric acid (C), or biological materials (D). Therefore, A is the correct choice for bypass fume hoods.

Correct Answer: C

Rationale: The correct answer is C because Clostridium perfringens is a Gram-positive rod-shaped bacterium, which matches the description provided. It is motile and peritrichous (having flagella all over the surface) without a capsule. This bacterium is known to cause gas gangrene due to its ability to produce toxins that destroy tissue. Choice A is incorrect because Clostridium perfringens is Gram-positive, not Gram-negative, and it does not have a capsule. Choice B is incorrect because Clostridium perfringens is not motile and does not have flagella all over its surface. Choice D is incorrect because Clostridium perfringens is Gram-positive, not Gram-negative, and it is motile without a capsule.

Correct Answer: A

Rationale: The correct answer is A: Tryptic soy agar is a general-purpose medium suitable for cultivating a wide range of microorganisms. It provides essential nutrients for growth without inhibiting specific types of bacteria. Blood agar (B), Mannitol salt agar (C), and MacConkey agar (D) are selective or differential media designed to promote the growth of specific types of bacteria or differentiate between different bacterial species. Therefore, they are not considered general-purpose mediums.

Correct Answer: B

Rationale: The correct answer is B: Staphylococcus aureus. This bacterium is a common causative agent of skin infections like carbuncles. Staphylococcus aureus is known for its ability to produce pus-filled abscesses, which aligns with the symptoms described in the question. The presence of a vesicular rash around the carbuncle further supports this diagnosis, as Staphylococcus aureus can cause skin lesions. The other choices are not correct because: A: Bacillus anthracis causes anthrax, which presents with different symptoms such as fever, malaise, and respiratory symptoms. C: Bacillus subtilis is a harmless soil bacterium commonly used in research and not known to cause skin infections. D: Bacillus anthracoides is not a known pathogen and is not associated with human infections.