Microbiology Test Bank

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: 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: C

Rationale: The correct answer is C: Leishmaniasis. The description of thin microorganisms with 12-14 uniform tendrils, 10-13 micrometers in length, and pale pink color matches the characteristics of Leishmania parasites seen in Giemsa-stained samples. Leishmania parasites are known to have a distinctive appearance with pointed tips and a specific size range. Syphilis (choice A) is caused by Treponema pallidum, which appears as tightly coiled spirochetes, not tendrils. Trypanosomiasis (choice B) is caused by Trypanosoma parasites, which have a different morphology and staining pattern. Relapsing fever (choice D) is caused by Borrelia recurrentis, which does not match the description given. Therefore, the correct choice is C as the description aligns closely with the characteristic features of Leishmania parasites.

Correct Answer: A

Rationale: Rationale: 1. Epstein-Barr virus causes infectious mononucleosis due to primary infection. 2. Certain types of cancer, such as Burkitt lymphoma and nasopharyngeal carcinoma, are associated with Epstein-Barr virus through oncogenic mechanisms. 3. Chickenpox and shingles are caused by varicella-zoster virus (HHV3). 4. Roseola infantum is caused by human herpesvirus 6 (HHV6). Summary: Choice A is correct as Epstein-Barr virus is linked to infectious mononucleosis and specific cancers. Choices B, C, and D are incorrect as they are caused by different herpesviruses.

Correct Answer: B

Rationale: The correct answer is B: Escherichia coli. E. coli is a common bacterium found in the gastrointestinal tract and is a leading cause of UTIs. It has specific virulence factors that enable it to adhere to and infect the urinary tract. Salmonella enterica causes food poisoning, Vibrio cholerae causes cholera, and Streptococcus pyogenes causes strep throat and skin infections, not UTIs. Therefore, B is the correct answer as it is the only bacterium known for causing UTIs.