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GI > Lower GI micro - viral, bacterial, parasitic > Flashcards

Lower GI micro - viral, bacterial, parasitic Flashcards

1
Q

What are the vaccines available for viral gastroenteritis?

A

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

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2
Q

Describe the epidemiology for Rotavirus?

A

winter, day care, fecal/oral spread

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3
Q

What is the tropism of Rotavirus?

A

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

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4
Q

Decribe symptoms of viral gastroenteritis from Norwalk virus?

A

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

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5
Q

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

A

enteric only!

poorly chlorinated pools

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6
Q

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

A

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

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7
Q

What is the mechanism of pathogenicity of Giardia lamblia?

A

loss of epithelial absorptive surface

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8
Q

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?

A

Giardia lamblia

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9
Q

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

A

contaminated water (ex. Boundary waters), filter water

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10
Q

How do you treat Giardiasis?

A

NItromidazole, NItazoxanide, Parmomycin

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11
Q

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?

A

Cryptosporidium parvum

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12
Q

How do you diagnose and treat Cryptosporoidiosis?

A

oocytes in stool, Nitazoxanide

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13
Q

Describe the symptoms for amebiasis?

A

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

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14
Q

Describe the pathogenisis/ life cycle of Entamoeba histolytica?

A

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

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15
Q

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

A

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

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16
Q

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

A

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

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17
Q

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

A

perianal pruritis, insomnia, anorexia, peritoneal granuloma, vulvovaginitis

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18
Q

Describe the pathogenesis/life cycle of Necatur/Hookworm

A

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

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19
Q

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

A

Necatur/Hookworm

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20
Q

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.

A

Trichuris/Whipworm

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21
Q

Describe the symptoms and dx for Ascaris (Giant roundworm)

A

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

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22
Q

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

A

1-7 hours

Toxin ID in stool or vomit

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23
Q

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

A

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

24
Q

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

A

Clostrdium Botulinm

25
Q

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

A

Clostridium perfingens

26
Q

What is the mechanism of infection for Clostridium perfingens?

A

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

27
Q

Describe the symptoms and diagnostic methods for campylobacter jejeuni

A

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

28
Q

How does salmonella enteritis cause diarrhea?

A

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

29
Q

What are diagnostic criteria for salmonella enteritisi?

A

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

30
Q

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

A

vivrio - similar to clostrdium and emetic bacillus cereus

31
Q

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

A

sx - fever, myalgia, meningitis, sepsis, liver infiltration?

most susceptible - pregnants, elderly, immunocomp.

32
Q

Name the 3 subtypes of shigella

A

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

33
Q

What is dysentery?

A

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

34
Q

Why is shigella dysentery more severe than sunni and flexnori?

A

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

35
Q

What are the symptoms for e coli gastroenteritis?

A 
Diarrhea
UTI
Neonatal sepsis
Gram (-) sepsis
also fever and nausea/vomiting
36
Q

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

A

etec - entero-toxogenic e coli

activates adenylateate cyclase, increase cAMP, decrease NA abso, increase CL excretion and water follows.

37
Q

Describe ehec mecahnism

A

enterohemorrhagic e coli

shiga toxin, does macrophage apoptosis and inflammatino, T3SS and actin rockets

38
Q

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

A

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

39
Q

Mechanism of vibrio cholera is just like what other bacteria?

A

Etec

40
Q

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?

A

Salmonella typhi causing typoid fever

41
Q

What is it called when c. diff becomes invasive

A

Pseudomembranous or fulminate colitis.

42
Q

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

A

Strongyloides

43
Q

Which nematode/roundworms infect via autoinfection?

A

Necator/Hookworm and Strongyloides (Nematode/roundworm)

44
Q

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

A

Enterobius burmicularis- pin worm

45
Q

What are the two longest tapeworms we have studied?

A

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

46
Q

What are some symptoms of Schistosomiasis?

A

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

47
Q

How do you prevent the spread of trematodes/flukes?

A

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

48
Q

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

A

Echinococcous

49
Q

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

A

Aminoglycoside antibiotic, SE: diarrhea

50
Q

Which drug is contraindicated in Cryptosporidiosus?

A

Nitromidazoles

51
Q

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

A

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

52
Q

What is the mechanism for Benzamidazoles and describe their specificity?

A

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

53
Q

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

A

Praziquantel

low efficacy against immature worms, necessitating second dose

54
Q

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

A

Nematodes and Ascaris strongyloides

55
Q

Why does macrocyclic lactone not affect human nerves and muscles?

A

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

56
Q

what is the mechanism of action for Benzimadazoles?

A

Bind beta tubulin

57
Q

What are the side effects of iodoquinol?

A

loss of visual acuity, thryoid disease cautions

GI (17 decks)

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