Lower GI micro - viral, bacterial, parasitic

Question 1

What are the vaccines available for viral gastroenteritis?

Answer 1

Rotavirus: 1. Rotarix, 2. Rotateq (bovine virus combo)
Adenovirus: live oral vaccine

Question 2

Describe the epidemiology for Rotavirus?

Answer 2

winter, day care, fecal/oral spread

Question 3

What is the tropism of Rotavirus?

Answer 3

infection of absorptive villous epithelium from upper 2/3 of sm. bowel to large intestine - uses NSP4

Question 4

Decribe symptoms of viral gastroenteritis from Norwalk virus?

Answer 4

fever > 101 F, HA, anorexia, malaise, diarrhea, N/V , highly infectious - only 10 particles needed for infection

Question 5

Describe the tropism of Adenovirus in viral gastroenteritis and where it might be acquired?

Answer 5

enteric only!

poorly chlorinated pools

Question 6

How could you differentiate an Adenovirus gastroenteritis from other viral gastroenteritis?

Answer 6

only rarely fever, amino assay, PCR - ds DNA linear (Norwalk= ds RNA and Rotavirus = ss + non-segmented RNA)

Question 7

What is the mechanism of pathogenicity of Giardia lamblia?

Answer 7

loss of epithelial absorptive surface

Question 8

Which lower GI parasite is associated with 1-2 wks. of foul, floating, flatulent diarrhea and can be diagnosed with id of cysts or trophozoites?

Answer 8

Giardia lamblia

Question 9

How is Giardia (beaver fever) contracted and how can it be prevented?

Answer 9

contaminated water (ex. Boundary waters), filter water

Question 10

How do you treat Giardiasis?

Answer 10

NItromidazole, NItazoxanide, Parmomycin

Question 11

What lower GI parasite impairs absorption and secretion in the epithelium causing fever and a watery non-bloody diarrhea, which can be fatal in HIV patients?

Answer 11

Cryptosporidium parvum

Question 12

How do you diagnose and treat Cryptosporoidiosis?

Answer 12

oocytes in stool, Nitazoxanide

Question 13

Describe the symptoms for amebiasis?

Answer 13

mucous bloody loose stool, liver- abscesses, fever, weight loss, RUQ pain

Question 14

Describe the pathogenisis/ life cycle of Entamoeba histolytica?

Answer 14

egg -> cyst -> trophozoite -> mucosal cell lysis in host -> blood stream -> liver

Question 15

Why is it important to treat Amebiasis with Iodoquinol or Parmomycin AND Nitromidazole?

Answer 15

Iodoquinol and Parmomycin are only effective in the lumen, Nitromidazole is effective in circulation

Question 16

How do you diagnose and treat (almost!) all roundworm/Nematode infections (and which one cannot be diagnosed the same way)?

Answer 16

eggs in stool - not Enterobius burmicularis (pin worms)- AM scotch tape test, Benzimidazoles

Question 17

What are the symptoms for Enterobius burmicularis (pin worms)?

Answer 17

perianal pruritis, insomnia, anorexia, peritoneal granuloma, vulvovaginitis

Question 18

Describe the pathogenesis/life cycle of Necatur/Hookworm

Answer 18

larvae in soil -> skin (penetration) -> blood stream -> lungs -> cough up -> reswallow

Question 19

Pruritic papillar erythematous rash and iron deficient anemia due to direct pathogen consumption are symptoms of what lower GI parasite?

Answer 19

Necatur/Hookworm

Question 20

Your patient comes back from winter in Florida with finger clubbing and bloody diarrhea, labs show iron deficient anemia and barrel shaped eggs in stool sample.

Answer 20

Trichuris/Whipworm

Question 21

Describe the symptoms and dx for Ascaris (Giant roundworm)

Answer 21

abdominal discomfort, intestinal block, cough, dx. - eggs with thick shell in stool, Charcot-Leyden crystals (non-specific)

Question 22

What is the length of onset and dx for s. aureus?

Answer 22

1-7 hours

Toxin ID in stool or vomit

Question 23

What are the 2 types of bacillus cereus and how do their pathogeneicites differ?

Answer 23

Emetic - preformed toxin that puts holes in the membrane, 1-6 hrs onset.
Diarrheal - large molecular weight toxin that causes osmotic toxin. 6-15 hrs

Question 24

Which gram positive bacillus has an neurotoxin that irreversible blocks Ach at motor end plate and forms spore

Answer 24

Clostrdium Botulinm

Question 25

What gram (+) bacillus is likely to be found buffet food and does not cause fever or vomiting. Sx usually lack 24 hours.

Answer 25

Clostridium perfingens

Question 26

What is the mechanism of infection for Clostridium perfingens?

Answer 26

Enterotoxins bind endothelical cell junction receptors and make pores in host mucosa.

Question 27

Describe the symptoms and diagnostic methods for campylobacter jejeuni

Answer 27

Bloody diarrhea, cramping, abdominal pain, fever for 1 week. Possible complication is Guilanne Barre. Gram (-) rod - karmal rod -

Question 28

How does salmonella enteritis cause diarrhea?

Answer 28

REplicates in cell walls and closes ion channels in the enterocytes and increases water and electrolyte excretion.

Question 29

What are diagnostic criteria for salmonella enteritisi?

Answer 29

Has flagella, gram (-) rod, lactose (-), sulfide (+) - Use ssalmonella shigella agar - H2S+ ferric citrate turns black for salmonella

Question 30

This GNR uses enterotxin and hemolysin to form pores in epithelium and RBC causing bloody diarrhea, cramps and fever, + N/v for less than one week

Answer 30

vivrio - similar to clostrdium and emetic bacillus cereus

Question 31

Describe the sx for listeria monocytogenes and which groups are most suceptible

Answer 31

sx - fever, myalgia, meningitis, sepsis, liver infiltration? | most susceptible - pregnants, elderly, immunocomp.

Question 32

Name the 3 subtypes of shigella

Answer 32

shigella Sonni - most common shigella Flexnori - causes bacilarry dysentery shigella Dystenteria - most severe

Question 33

What is dysentery?

Answer 33

inflammaotry gastroenteritis causing frequent small bm, rectal pain and reactive arthritis

Question 34

Why is shigella dysentery more severe than sunni and flexnori?

Answer 34

All invasive and cause macrophage apoptois and have T3ss but dystenery also has phage bourne shiga (vera) toxin that works on vascular endothelial cells

Question 35

What are the symptoms for e coli gastroenteritis?

Answer 35

``` Diarrhea UTI Neonatal sepsis Gram (-) sepsis also fever and nausea/vomiting ```

Question 36

Which e.coli causes traveler's diarrhea. And what is the mechanism?

Answer 36

etec - entero-toxogenic e coli | activates adenylateate cyclase, increase cAMP, decrease NA abso, increase CL excretion and water follows.

Question 37

Describe ehec mecahnism

Answer 37

enterohemorrhagic e coli | shiga toxin, does macrophage apoptosis and inflammatino, T3SS and actin rockets

Question 38

Which serotypes of vibrio cause cholera? What are the sx?

Answer 38

Sero groups 1 and 139. Symptoms include ricewater stool, vomiting + symptoms of dehydration

Question 39

Mechanism of vibrio cholera is just like what other bacteria?

Answer 39

Etec

Question 40

What GI pathogen is found in untreated water and causes a life threatening fever, stomach pain, diarrhea/constipation, flat rose colored rash and invades the bloodstream?

Answer 40

Salmonella typhi causing typoid fever

Question 41

What is it called when c. diff becomes invasive

Answer 41

Pseudomembranous or fulminate colitis.

Question 42

Which nematode/roundworm causes a raised red rash on the thighs and butt, stomach ache, GI/respiratory problems?

Answer 42

Strongyloides

Question 43

Which nematode/roundworms infect via autoinfection?

Answer 43

Necator/Hookworm and Strongyloides (Nematode/roundworm)

Question 44

What is the most common day care nematode/roundworm infection?

Answer 44

Enterobius burmicularis- pin worm

Question 45

What are the two longest tapeworms we have studied?

Answer 45

Diphyllobothrium (fish) up to 30 ft. and Taenia (cysticercosis) up to 10 m

Question 46

What are some symptoms of Schistosomiasis?

Answer 46

days- red itchy skin months- fever, chills, cough, myalgia chronic- abdominal pain, hepatomegaly, bloody stool/urine, kids (malnutrition, anemia, learning difficulties)

Question 47

How do you prevent the spread of trematodes/flukes?

Answer 47

improve sanitation, don't swim in contaminated water, mass admin. of praziquantel

Question 48

Which nematode is associated with sheep farming and close living with dogs?

Answer 48

Echinococcous

Question 49

What type of drug is Parmomycin and what side effects does it have?

Answer 49

Aminoglycoside antibiotic, SE: diarrhea

Question 50

Which drug is contraindicated in Cryptosporidiosus?

Answer 50

Nitromidazoles

Question 51

What classes of drugs are used to treat GI nematode/roundworm infections?

Answer 51

Benzamidazole and cholinergic antihelminths (cause paralysis- Levamasol and Pyrantel pamoate)

Question 52

What is the mechanism for Benzamidazoles and describe their specificity?

Answer 52

Mech: bind parasite beta tubulin Specificity: protozoa have different tubulin than eukaryokes

Question 53

What is the drug of choice for tapeworms and some limitations?

Answer 53

Praziquantel | low efficacy against immature worms, necessitating second dose

Question 54

Macrocyclic lactone binds chloride channels on nerve and muscle cells of these organisms?

Answer 54

Nematodes and Ascaris strongyloides

Question 55

Why does macrocyclic lactone not affect human nerves and muscles?

Answer 55

the target chloride channels are solely located in the CNS in humans and macrocyclic lactone does not cross the BBB

Question 56

what is the mechanism of action for Benzimadazoles?

Answer 56

Bind beta tubulin

Question 57

What are the side effects of iodoquinol?

Answer 57

loss of visual acuity, thryoid disease cautions