DEPARTMENT OF MEDICAL MICROBIOLOGY & PARASIT..

### M**ount Kenya University** **UNIVERSITY EXAMINATION 2022/2023****MEDICAL SCHOOL****DEPARTMENT OF MEDICAL MICROBIOLOGY** **BACHELOR OF MEDICINE AND BACHELOR OF SURGERY (MBChB)****UNIT CODE**: MBMM 2400**UNIT TITLE**: Principles of Microbiology and Parasitology**DATE**: Tuesday, 11th July 2023**TIME**: 8:00 AM – 10:00 AM**DURATION**: 2 Hours --- ### **INSTRUCTIONS** - **Answer all questions in Sections A and B.** - **Answer any TWO (2) questions in Section C.** --- ## **SECTION A: MULTIPLE CHOICE QUESTIONS (35 MARKS)** # ## Principles of Microbiology and Parasitology & Medical Parasitology ### **Complete MCQ Answer Key with Explanations** --- ## SECTION A: PARASITOLOGY MCQs ### **1. Nitazoxanide is BEST for treatment of?** **Options:** - A. Amoebiasis - B. Trichomoniasis - C. Giardiasis - D. Chagas disease - E. Loasis **Answer: C. Giardiasis** **Explanation:** Nitazoxanide is a broad-spectrum antiparasitic drug that is particularly effective against Giardia lamblia. While it has some activity against other parasites, its primary indication and best efficacy is for giardiasis treatment. **Why other options are incorrect:** - A. Amoebiasis: Metronidazole is the drug of choice - B. Trichomoniasis: Metronidazole is the preferred treatment - D. Chagas disease: Benznidazole or nifurtimox are used - E. Loasis: Diethylcarbamazine (DEC) is the treatment of choice --- ### **2. Metronidazole parasite site of target is?** **Options:** - A. RNA - B. DNA - C. Ribosomes - D. Cytoskeleton **Answer: B. DNA** **Explanation:** Metronidazole is activated by reduction in anaerobic organisms, forming reactive intermediates that damage DNA by causing strand breaks and preventing DNA replication. **Why other options are incorrect:** - A. RNA: Not the primary target of metronidazole - C. Ribosomes: Target of antibiotics like chloramphenicol, not metronidazole - D. Cytoskeleton: Target of drugs like benzimidazoles, not metronidazole --- ### **3. Which parasite causes vitamin B12 deficiency?** **Options:** - A. Ancylostoma braziliense - B. Toxocara canis - C. Enterobium vermicularis - D. Diphyllobothrium latum **Answer: D. Diphyllobothrium latum** **Explanation:** Diphyllobothrium latum (fish tapeworm) causes vitamin B12 deficiency by competing with the host for vitamin B12 absorption in the small intestine, potentially leading to megaloblastic anemia. **Why other options are incorrect:** - A. Ancylostoma braziliense: Causes cutaneous larva migrans - B. Toxocara canis: Causes visceral larva migrans - C. Enterobium vermicularis: Causes pinworm infection with perianal itching --- ### **4. Which of the following parasites is associated with achlorhydria?** **Options:** - A. Dientamoeba fragilis - B. Trichomonas vaginalis - C. Giardia intestinalis - D. Leishmania tropica - E. Toxoplasma gondii **Answer: C. Giardia intestinalis** **Explanation:** Giardia intestinalis is associated with achlorhydria (absence of gastric acid) as the low acid environment facilitates Giardia survival and establishment in the small intestine. **Why other options are incorrect:** - A. Dientamoeba fragilis: Causes colitis, not associated with achlorhydria - B. Trichomonas vaginalis: Urogenital parasite, not related to gastric acid - D. Leishmania tropica: Causes cutaneous leishmaniasis - E. Toxoplasma gondii: Intracellular parasite, not gastric-related --- ### **5. Which of the following parasites is associated with pyosalpingitis?** **Options:** - A. Amoeba species - B. Trichomonas species - C. Giardia species - D. Leishmania species - E. Onchocerca volvulus **Answer: B. Trichomonas species** **Explanation:** Trichomonas vaginalis can cause ascending urogenital infections leading to pyosalpingitis (infection of the fallopian tubes) and pelvic inflammatory disease. **Why other options are incorrect:** - A. Amoeba species: Primarily cause intestinal or hepatic infections - C. Giardia species: Intestinal parasite, not urogenital - D. Leishmania species: Cause cutaneous, mucocutaneous, or visceral leishmaniasis - E. Onchocerca volvulus: Causes river blindness --- ### **6. Ground itch is produced by?** **Options:** - A. Necator americanus - B. Ascaris lumbricoides - C. Enterobium vermicularis - D. Diphyllobothrium latum **Answer: A. Necator americanus** **Explanation:** Ground itch is caused by skin penetration of hookworm larvae, particularly Necator americanus and Ancylostoma duodenale, as they enter through bare feet in contact with contaminated soil. **Why other options are incorrect:** - B. Ascaris lumbricoides: Transmitted through ingestion of eggs, not skin penetration - C. Enterobium vermicularis: Transmitted through ingestion of eggs - D. Diphyllobothrium latum: Transmitted through eating undercooked fish --- ### **7. Which one is associated with nocturnal pruritus ani?** **Options:** - A. Necator americanus - B. Ascaris lumbricoides - C. Enterobium vermicularis - D. Diphy