Nokea
A patient with diarrhea had stool microscopy revealing large, oval protozoa with a single nucleus and four flagella. What is the most likely causative agent?
- A. Giardia lamblia
- B. Entamoeba histolytica
- C. Balantidium coli
- D. Trichomonas vaginalis
Correct Answer: A
Rationale: Step 1: Large, oval protozoa with a single nucleus and four flagella indicate Giardia lamblia.
Step 2: Giardia lamblia is a flagellated protozoan causing diarrhea.
Step 3: It has a distinct appearance under microscopy.
Step 4: Entamoeba histolytica causes dysentery with no flagella.
Step 5: Balantidium coli is a ciliated protozoan with a larger size.
Step 6: Trichomonas vaginalis lacks a cyst stage and causes genitourinary infections.
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Sanitary control is applied to monitor the quality of:
- A. Food, drinking water, restaurants, health care services and transport
- B. Food, drinking water
- C. Food, drinking water, restaurants and health care services
- D. Food, drinking water, and restaurants
Correct Answer: A
Rationale: The correct answer is A because sanitary control is crucial for monitoring the quality of a wide range of essential services to ensure public health and safety. Food safety, drinking water quality, cleanliness in restaurants, hygiene in healthcare settings, and transportation systems all fall under the purview of sanitary control. Therefore, option A is the most comprehensive and accurate choice.
Option B is incorrect because it does not include monitoring restaurants, health care services, and transport, which are important aspects of sanitary control. Option C is incorrect as it excludes transportation, an essential area that requires sanitary monitoring. Option D is incorrect as it does not cover health care services, which are critical for ensuring public health and safety.
Which of the following proteins are encoded by herpesviruses and required for viral DNA replication
- A. viral DNA polymerase
- B. ribonucleotide reductase
- C. neuraminidase
- D. thymidine kinase
Correct Answer: A
Rationale: The correct answer is A: viral DNA polymerase. Herpesviruses require viral DNA polymerase for viral DNA replication. This enzyme is responsible for synthesizing new DNA strands using existing viral DNA as a template. Ribonucleotide reductase (B) is not directly involved in DNA replication but in the synthesis of deoxyribonucleotides. Neuraminidase (C) is an enzyme found in influenza viruses, not herpesviruses. Thymidine kinase (D) is involved in nucleotide metabolism but is not essential for viral DNA replication in herpesviruses.
Which organism produces a toxin that blocks neuromuscular transmission in cholinergic motor neurons:
- A. Shigella dysenteriae
- B. Clostridium tetani
- C. Corynebacterium diphtheria
- D. Clostridium botulinum
Correct Answer: D
Rationale: The correct answer is D: Clostridium botulinum. This bacterium produces botulinum toxin, which blocks neuromuscular transmission by inhibiting the release of acetylcholine at the neuromuscular junction. This leads to muscle weakness and paralysis. Shigella dysenteriae (A) causes dysentery but does not affect neuromuscular transmission. Clostridium tetani (B) produces tetanus toxin, which affects inhibitory neurons in the spinal cord, leading to muscle spasm. Corynebacterium diphtheriae (C) produces diphtheria toxin, which affects protein synthesis in cells, not neuromuscular transmission.
The causative agent of typhoid fever is:
- A. Shigella dysenteriae
- B. Vibrio cholerae
- C. Salmonella typhi
- D. Escherichia coli
Correct Answer: C
Rationale: The correct answer is C: Salmonella typhi. Typhoid fever is caused by the bacterium Salmonella typhi, specifically transmitted through contaminated food and water. Shigella dysenteriae causes bacillary dysentery, Vibrio cholerae causes cholera, and Escherichia coli can cause various gastrointestinal illnesses, but not typhoid fever. Identifying the causative agent is crucial for effective treatment and prevention strategies.
Trichinosis is an infection caused by ingestion of a:
- A. nematode
- B. virus
- C. bacteria
- D. fungus
Correct Answer: A
Rationale: The correct answer is A: nematode. Trichinosis is caused by the roundworm Trichinella spiralis, a type of nematode. Nematodes are multicellular parasites commonly found in raw or undercooked meat. Viruses, bacteria, and fungi do not cause trichinosis. Viruses are not parasitic worms, bacteria are single-celled organisms, and fungi are eukaryotic organisms distinct from nematodes. Therefore, the ingestion of nematodes, not viruses, bacteria, or fungi, leads to trichinosis.