mastering microbiology test bank

Correct Answer: A

Rationale: Flagella are the correct answer because they are long, whip-like structures that aid in bacterial movement towards or away from chemical stimuli. They rotate like propellers, allowing the bacterium to navigate its environment. Pili are used for attachment, not movement. Capsules are involved in protection and adherence, not chemotaxis. Fimbriae help in attachment to surfaces, not in movement towards stimuli.

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: A

Rationale: The correct answer is A: Late congenital syphilis. The symptoms described align with late congenital syphilis, which includes saddle nose, high-arched palate, natiform skull, peg-shaped incisors, and notched cutting edge. Lymph nodes not being affected is also consistent with late congenital syphilis. Early congenital syphilis (B) typically presents with more severe symptoms at birth or shortly after. Tertiary syphilis (C) usually occurs years after initial infection and presents with different symptoms. Fluorosis (D) is caused by excessive fluoride intake and does not match the symptoms described.

Correct Answer: A

Rationale: The correct answer is A: Amoxicillin. Amoxicillin is commonly used in combination therapy with metronidazole and bismuth compounds like De-Nol to eradicate Helicobacter pylori infection in children. Amoxicillin targets the bacterial cell wall synthesis, working synergistically with metronidazole to effectively eradicate the infection. Tetracycline (choice B) is not recommended in children under 8 years old due to potential tooth discoloration. Oleandomycin (choice C) is not commonly used for H. pylori infection. Biseptol (choice D) is a combination of sulfamethoxazole and trimethoprim, not typically used for H. pylori eradication.

Correct Answer: B

Rationale: The correct answer is B: Cell-wall regrowth. This is not a bacterial antibiotic resistance mechanism because antibiotics target specific components in bacteria, such as cell wall synthesis, making regrowth impossible in the presence of antibiotics. Reduced permeability (A) decreases antibiotic entry, Over-expression of target (C) reduces antibiotic effectiveness, and Efflux pump (D) actively removes antibiotics from the cell, all contributing to antibiotic resistance. In summary, cell-wall regrowth is not a mechanism of antibiotic resistance, unlike the other choices that actively promote bacterial survival against antibiotics.