SYTM 5505 Week 4 A & B Practice 150+Questions and Verified Correct Answer. 100% A+ Grade TOPSCORE 2024 NEW GENERATION!!!

SYTM 5505 Week 4 A & B Practice 150+Questions and Verified Correct Answer. 100% A+ Grade TOPSCORE 2024 NEW GENERATION!!!
[4AB] A 2-year-old boy was brought to the hospital with dehydration and severe diarrhea of 3 days duration. His watery diarrhea did not resolve despite taking antibiotics for 3 days. His stools were examined under the electron microscope and it appeared as wheel-shaped virions. Which one of the following is the most likely microbial cause of his illness?
A: Hepatitis A virus
B: Rotavirus
C: Entamoeba histolytica
D: Ebola virus
E: Polio virus - CORRECT ANSWER>>B: Rotavirus
Rotavirus infects small intestine, attacking mature, non-dividing enterocytes in middle & tip of villi. VP4 binds to host receptor to facilitate viral entry. Once inside, viral replication takes place & NSP4 enterotoxin is produced. New viruses are released & continue to cause infections, leading to enterocyte damage & death. This causes osmotic diarrhea, while NSP4 causes secretory diarrhea by binding to Ca2+ mediated Cl- channels. There is also activation of enteric nervous system, increasing motility and vomiting. Thus, it presents with fever, vomiting, watery diarrhea, & rapid dehydration lasting 3-6 days. It causes extra-intestinal infections & potentially recurrent infections in immunocompromised patients.

[4AB] A 22-year-old woman presents to the physician aboard a cruise ship complaining of fever, vomiting, and diarrhea. The symptoms started three days ago after eating shellfish for dinner. Vital signs are significant for tachycardia. Physical examination reveals mild abdominal discomfort without guarding or rebound tenderness. Pupillary light reflexes are intact and sclerae are white. Fecal occult blood testing is negative and fecal leukocytes are absent from the stool. Viral PCR reveals a single-stranded RNA genome. Which of the following is the most likely causative agent?
A: Rhinovirus
B: Togavirus
C: Hepadnavirus
D: Calicivirus
E: Filovirus - CORRECT ANSWER>>D: Calicivirus
Norovirus aka winter vomiting disease is non-enveloped, positive sense ssRNA virus. It has capsid containing VP1. It is most common cause of acute gastroenteritis in developed & developing countries. It affects all ages & outbreaks are more common in winter, hence its name. It is able to withstand wide range of temperatures, pH, disinfectants, waters, & foods, so its infectious dose is very low. There are multiple modes of transmission (fecal-oral is primary), & humans are its only host. It is highly contagious, w/ viral shedding lasting up to 56 days. There is no long-term immunity or vaccine b/c there are so many strains & Norovirus undergoes antigenic shift. Little is known of its pathogenesis b/c there is no animal model. However, biopsy shows blunted villi, cytoplasmic vacuolization, & leukocytic infiltration of small intestine. All this is reversible once infection is gone. Infection also causes transient malabsorption, decreased activity of enzymes, & osmotic diarrhea. It presents w/ fever, myalgia, vomiting, & watery diarrhea for 1-3 days. Lab diagnosis is done using ELISA (viral antigen), PCR (viral RNA), or EM (viral particle). Treatment is oral fluid replacement.

[4AB] An 18-year-old man presents to the doctor with cramping abdominal pain, low grade fever and diarrhea with bulky, foul-smelling stools for the past 4 days. Stools were observed under the light microscope and showed pear-shaped organisms. Which of the following organisms is the most likely cause of his illness?
A: Entamoeba histolytica
B: Giardia lamblia
C: Isospora belli
D: Cryptosporidium parvum
E: Taenia saginata - CORRECT ANSWER>>B: Giardia lamblia
G. intestinalis is most common intestinal parasite in U.S. Transmission is water-borne, person-to-person, & sexual. It is assoc. w/ poor sanitation, camping, & child care centers. It is one cause of traveler's diarrhea. It exists as either oval cyst (quadrinucleated if mature, binucleated if immature) or flagellated trophozoite w/ sucking disk. Trophozoite has falling leaf motility & is visualized using Giemsa stain. Cyst is ingested & undergoes excystation in small intestine. Trophozoites replicate by binary fission & eventually undergo encystation. Both trophozoites & cysts are excreted in feces, though cysts are ones that propagate life cycle.

[4AB] A 16-year-old girl presents to clinic with a 3-day history of abdominal pain and constipation. She recently returned from a vacation to South America. She denies episodes of emesis or bloody stools. On exam, he has a temperature of 38.2°C (100.8°F) and abdominal tenderness in all four quadrants. A CBC demonstrates eosinophilia. Abdominal x-ray shows a small bowel obstruction at the ileocecal valve without evidence of volvulus, intussusception, or other specific etiology. Stool microscopy demonstrates brown, oval-shaped ova. Which of the follow is the most likely causative pathogen?
A: Enterobius vermicularis
B: Ascaris lumbricoides
C: Ancylostoma duodenale
D: Strongyloides stercoralis
E: Echinococcus granulosus - CORRECT ANSWER>>B: Ascaris lumbricoides
Roundworm infection begins when human swallows Ascaris eggs, which hatch in small intestine & are absorbed into systemic circulation. Larvae enter lungs, where they develop into adult worms. They then climb up trachea to be swallowed back into GI tract so that they can lay eggs that are excreted thru feces. Infection may be asymptomatic, but intestinal stages can cause abdominal pain, nausea, poor digestion, & blockage if there are large numbers of worms. They can also cause respiratory distress & hypersensitivity reactions.