free microbiology test bank questions pdf

Correct Answer: A

Rationale: The correct answer is A: Entamoeba histolytica. This pathogen is known to cause amoebic dysentery, characterized by diarrhea with bloody or mucoid stools. The presence of cysts with four nuclei in the stool microscopy is a characteristic feature of Entamoeba histolytica. Other choices are incorrect because Giardia lamblia typically presents with binucleate cysts, Balantidium coli is a ciliated protozoan, and Trichomonas hominis is a non-pathogenic parasite found in the human intestine.

Correct Answer: D

Rationale: The correct answer is D: rectum. Pinworms typically inhabit the rectum area in humans, where they lay their eggs. This is because the female pinworm migrates to the rectum at night to deposit her eggs near the anus. Other choices are incorrect because pinworms do not reside in the duodenum (A), ileum (B), or transverse colon (C) as their primary location is in the lower gastrointestinal tract near the anus.

Correct Answer: B

Rationale: The correct answer is B: Typhoid fever. Typhoid fever is transmitted through the fecal-oral route, meaning the bacteria from an infected person's feces can contaminate food or water and then be ingested by another person. This can lead to infection and illness. The other choices, diphtheria (A), syphilis (C), and spotted fever (D) are not transmitted through the fecal-oral route. Diphtheria is spread through respiratory droplets, syphilis is primarily sexually transmitted, and spotted fever is transmitted through tick bites. Thus, only Typhoid fever aligns with the fecal-oral route of transmission.

Correct Answer: C

Rationale: The correct answer is C: Corynebacterium diphtheriae. This bacterium causes diphtheria, a disease characterized by a pseudomembrane in the throat. This pseudomembrane is a result of the bacterial exotoxins causing inflammation and necrosis of the throat tissues. Clostridium tetani (A) causes tetanus, characterized by muscle stiffness, not a pseudomembrane in the throat. Bordetella pertussis (B) causes whooping cough, with symptoms of severe coughing fits but no pseudomembrane. Streptococcus pyogenes (D) causes strep throat, but does not produce a pseudomembrane.

Correct Answer: A

Rationale: Rationale: 1. Unicellular organisms with two layers in cytoplasm = Entamoeba gingivalis. 2. Wide pseudopodia = characteristic of Entamoeba genus. 3. Entamoeba histolytica causes amoebic dysentery, not dental plaque. 4. Trichomonas tenax causes periodontal disease, not dental plaque. 5. Lamblia intestinalis causes giardiasis, not related to dental plaque.