microbiology test bank

Correct Answer: A

Rationale: Aminoglycosides primarily inhibit protein synthesis by binding to the 30S ribosomal subunit in bacteria. This action leads to misreading of mRNA and ultimately disrupts the translation process, resulting in faulty protein production and bacterial cell death. Incorrect choices: B: Aminoglycosides do not inhibit DNA replication. C: Aminoglycosides do not disrupt cell membrane integrity. D: Aminoglycosides do not inhibit folic acid synthesis. In summary, the correct choice (A) aligns with the known mechanism of action of aminoglycosides, making it the most appropriate answer.

Correct Answer: A

Rationale: The correct answer is A: prions. Prions are misfolded proteins that can cause spongiform encephalopathy by inducing normal proteins to misfold as well. Prions lack genetic material, distinguishing them from viruses (B), bacteria (C), and fungi (D), which all contain genetic material and cannot directly cause spongiform encephalopathy through protein misfolding.

Correct Answer: A

Rationale: The correct answer is A: Bacterial vaginosis (gardnerellosis). The presence of clue cells on the Gram-stained smears is characteristic of bacterial vaginosis. Clue cells are vaginal epithelial cells covered with bacteria, specifically Gardnerella vaginalis, which is the causative agent of bacterial vaginosis. The symptoms described by the patient - itching, burning, watery discharge with a fish-like smell - are classic signs of bacterial vaginosis. The absence of alterations in the cervix, uterus, and appendages rules out other sexually transmitted infections like chlamydiosis, gonorrhea, and trichomoniasis. Therefore, the most likely pathology in this case is bacterial vaginosis.

Correct Answer: A

Rationale: The correct answer is A: Entamoeba histolytica. This is because Entamoeba histolytica is known to cause amebic dysentery, leading to chronic diarrhea. The presence of cysts with four nuclei in the stool sample is characteristic of Entamoeba histolytica. Giardia lamblia (choice B) is known to cause diarrhea but does not present with cysts containing four nuclei. Balantidium coli (choice C) is a ciliated protozoan that can cause diarrhea, but it does not have cysts with four nuclei. Trichomonas hominis (choice D) is a non-pathogenic protozoan commonly found in the human colon and is not associated with causing chronic diarrhea or cysts with four nuclei.

Correct Answer: D

Rationale: The correct answer is D: To determine the children that need to receive BCG vaccination. The Mantoux test is used to identify individuals who have been exposed to Tuberculosis (TB) and need BCG vaccination for protection. Parotitis (choice A) is a viral infection unrelated to TB. Allergization rate toward rickettsia (choice B) and immune stress toward diphtheria (choice C) are not related to the Mantoux test or BCG vaccination. Therefore, choice D is the correct answer as it aligns with the purpose of the Mantoux test.