Examination of duodenal contents revealed some pyriform protozoa with twin nuclei and four pairs of flagella. There were two supporting filaments between the nuclei and a suctorial disc on the ventral side. What representative of protozoa was revealed in this patient?

Correct Answer: A

Rationale: Rationale for Correct Answer A (Lamblia): 1. Pyriform protozoa with twin nuclei, four pairs of flagella, and a suctorial disc match the characteristics of Giardia lamblia. 2. The presence of two supporting filaments between the nuclei is a unique feature of Giardia lamblia. 3. Giardia lamblia is known to infect the duodenum and cause symptoms such as diarrhea and abdominal pain. Summary of Incorrect Choices: B: Toxoplasma - Toxoplasma gondii is not characterized by four pairs of flagella or supporting filaments in the nuclei. C: Leishmania - Leishmania species do not typically have the described morphology or location in the duodenum. D: Intestinal trichomonad - Intestinal trichomonads do not exhibit the specific features mentioned in the question, such as twin nuclei and supporting filaments.

Correct Answer: D

Rationale: The correct answer is D: All of the above. Hospital-acquired infections can be caused by a variety of bacteria commonly found in healthcare settings. Staphylococcus aureus is a common cause of surgical site infections. Escherichia coli can cause urinary tract infections. Klebsiella pneumoniae is associated with pneumonia and bloodstream infections. Therefore, all three bacteria are frequently implicated in hospital-acquired infections due to their prevalence and ability to cause different types of infections in healthcare settings. Thus, the correct answer is D, as all of the listed bacteria are commonly associated with hospital-acquired infections.

Correct Answer: B

Rationale: The correct answer is B: Candida albicans. Candida albicans is the most common cause of vaginal yeast infections due to its ability to overgrow in warm, moist environments like the vagina. It is a type of fungus that naturally resides in the body, but can cause infection when its growth is not regulated. Histoplasma capsulatum (A) causes a lung infection, Aspergillus niger (C) causes fungal sinusitis, and Saccharomyces cerevisiae (D) is a type of yeast used in baking and brewing, not typically associated with vaginal infections.

Correct Answer: D

Rationale: The correct answer is D: All of the above. The cytoplasmic membrane of prokaryotes consists of phospholipids which form a lipid bilayer, providing structure and selective permeability. Proteins are embedded in this membrane, serving various functions like transport and signaling. Carbohydrates may also be present on the surface for cell recognition. Therefore, all three components (phospholipids, proteins, and carbohydrates) are essential parts of the prokaryotic cytoplasmic membrane. Option A, B, and C individually do not fully encapsulate the complexity and composition of the prokaryotic cytoplasmic membrane.

Correct Answer: B

Rationale: Rationale: 1. Enteropathogenic E.coli (EPEC) adheres to the intestinal wall using bundle-forming pili. 2. EPEC produces toxins that disrupt cell structure and function, leading to diarrhea. 3. Shigella spp. invade intestinal cells, Salmonella spp. invade and multiply within cells, and Vibrio cholerae produces cholera toxin causing profuse watery diarrhea. Summary: A, C, and D choices are incorrect because they do not specifically adhere to the intestine wall and produce toxins like EPEC does.

Correct Answer: A

Rationale: The correct answer is A: Metronidazole. Metronidazole is the drug of choice for amebic dysentery as it effectively targets the protozoa causing the infection. It has good tissue penetration and high efficacy against Entamoeba histolytica. Pyrantel (B) is used for nematode infections, not amebiasis. Levamisole (C) is an anthelmintic for roundworms and not effective against amoebas. Bicillin-5 (D) is a penicillin antibiotic, which is not indicated for treating amebic dysentery.

Correct Answer: C

Rationale: The correct answer is C, transplacental mechanism. Listeria monocytogenes can cross the placenta, infecting the fetus during pregnancy. This mechanism allows the bacteria to be transmitted from mother to baby in utero. Alimentary mechanism (A) involves ingestion of contaminated food, not direct transfer between individuals. Transmission (B) is a broad term that doesn't specify the specific route of Listeria transmission. Physical contact (D) is not a common mode of Listeria transmission compared to transplacental transmission in the case of maternal-fetal infection.

Correct Answer: B

Rationale: The correct answer is B: Agglutination reaction. This test is commonly used to detect specific antibodies or antigens. In this case, it can be used to detect plague antigens in the rat tissues or antibodies in the villagers. This test is rapid, sensitive, and can help establish the presence of the causative agent quickly. A: Ring precipitation reaction is not typically used for diagnosing plague and is more commonly used in other types of infections. C: Passive agglutination reaction is not specific for plague and is more commonly used for detecting specific antibodies in diseases like syphilis. D: Neutralization reaction is not typically used for diagnosing plague and is more commonly used to determine the presence of neutralizing antibodies in viral infections.

Correct Answer: C

Rationale: Step-by-step rationale: 1. Shigella is a nonmotile bacterium. 2. This lack of motility is a key characteristic used to differentiate it from other enteric bacteria. 3. Nonmotile nature of Shigella helps it to cause infections by invading the intestinal epithelial cells. 4. Therefore, choice C is correct as Shigella is indeed nonmotile. Summary: A: Incorrect - Shigella does not produce hydrogen sulfide. B: Incorrect - Shigella does not ferment lactose. D: Incorrect - Shigella is not mannitol positive.