Lower GI micro - viral, bacterial, parasitic Flashcards
What are the vaccines available for viral gastroenteritis?
Rotavirus: 1. Rotarix, 2. Rotateq (bovine virus combo)
Adenovirus: live oral vaccine
Describe the epidemiology for Rotavirus?
winter, day care, fecal/oral spread
What is the tropism of Rotavirus?
infection of absorptive villous epithelium from upper 2/3 of sm. bowel to large intestine - uses NSP4
Decribe symptoms of viral gastroenteritis from Norwalk virus?
fever > 101 F, HA, anorexia, malaise, diarrhea, N/V , highly infectious - only 10 particles needed for infection
Describe the tropism of Adenovirus in viral gastroenteritis and where it might be acquired?
enteric only!
poorly chlorinated pools
How could you differentiate an Adenovirus gastroenteritis from other viral gastroenteritis?
only rarely fever, amino assay, PCR - ds DNA linear (Norwalk= ds RNA and Rotavirus = ss + non-segmented RNA)
What is the mechanism of pathogenicity of Giardia lamblia?
loss of epithelial absorptive surface
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?
Giardia lamblia
How is Giardia (beaver fever) contracted and how can it be prevented?
contaminated water (ex. Boundary waters), filter water
How do you treat Giardiasis?
NItromidazole, NItazoxanide, Parmomycin
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?
Cryptosporidium parvum
How do you diagnose and treat Cryptosporoidiosis?
oocytes in stool, Nitazoxanide
Describe the symptoms for amebiasis?
mucous bloody loose stool, liver- abscesses, fever, weight loss, RUQ pain
Describe the pathogenisis/ life cycle of Entamoeba histolytica?
egg -> cyst -> trophozoite -> mucosal cell lysis in host -> blood stream -> liver
Why is it important to treat Amebiasis with Iodoquinol or Parmomycin AND Nitromidazole?
Iodoquinol and Parmomycin are only effective in the lumen, Nitromidazole is effective in circulation
How do you diagnose and treat (almost!) all roundworm/Nematode infections (and which one cannot be diagnosed the same way)?
eggs in stool - not Enterobius burmicularis (pin worms)- AM scotch tape test, Benzimidazoles
What are the symptoms for Enterobius burmicularis (pin worms)?
perianal pruritis, insomnia, anorexia, peritoneal granuloma, vulvovaginitis
Describe the pathogenesis/life cycle of Necatur/Hookworm
larvae in soil -> skin (penetration) -> blood stream -> lungs -> cough up -> reswallow
Pruritic papillar erythematous rash and iron deficient anemia due to direct pathogen consumption are symptoms of what lower GI parasite?
Necatur/Hookworm
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.
Trichuris/Whipworm
Describe the symptoms and dx for Ascaris (Giant roundworm)
abdominal discomfort, intestinal block, cough, dx. - eggs with thick shell in stool, Charcot-Leyden crystals (non-specific)
What is the length of onset and dx for s. aureus?
1-7 hours
Toxin ID in stool or vomit
What are the 2 types of bacillus cereus and how do their pathogeneicites differ?
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
Which gram positive bacillus has an neurotoxin that irreversible blocks Ach at motor end plate and forms spore
Clostrdium Botulinm
What gram (+) bacillus is likely to be found buffet food and does not cause fever or vomiting. Sx usually lack 24 hours.
Clostridium perfingens
What is the mechanism of infection for Clostridium perfingens?
Enterotoxins bind endothelical cell junction receptors and make pores in host mucosa.
Describe the symptoms and diagnostic methods for campylobacter jejeuni
Bloody diarrhea, cramping, abdominal pain, fever for 1 week. Possible complication is Guilanne Barre.
Gram (-) rod - karmal rod -
How does salmonella enteritis cause diarrhea?
REplicates in cell walls and closes ion channels in the enterocytes and increases water and electrolyte excretion.
What are diagnostic criteria for salmonella enteritisi?
Has flagella, gram (-) rod, lactose (-), sulfide (+) - Use ssalmonella shigella agar - H2S+ ferric citrate turns black for salmonella
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
vivrio - similar to clostrdium and emetic bacillus cereus
Describe the sx for listeria monocytogenes and which groups are most suceptible
sx - fever, myalgia, meningitis, sepsis, liver infiltration?
most susceptible - pregnants, elderly, immunocomp.
Name the 3 subtypes of shigella
shigella Sonni - most common
shigella Flexnori - causes bacilarry dysentery
shigella Dystenteria - most severe
What is dysentery?
inflammaotry gastroenteritis causing frequent small bm, rectal pain and reactive arthritis
Why is shigella dysentery more severe than sunni and flexnori?
All invasive and cause macrophage apoptois and have T3ss but dystenery also has phage bourne shiga (vera) toxin that works on vascular endothelial cells
What are the symptoms for e coli gastroenteritis?
Diarrhea UTI Neonatal sepsis Gram (-) sepsis also fever and nausea/vomiting
Which e.coli causes traveler’s diarrhea. And what is the mechanism?
etec - entero-toxogenic e coli
activates adenylateate cyclase, increase cAMP, decrease NA abso, increase CL excretion and water follows.
Describe ehec mecahnism
enterohemorrhagic e coli
shiga toxin, does macrophage apoptosis and inflammatino, T3SS and actin rockets
Which serotypes of vibrio cause cholera? What are the sx?
Sero groups 1 and 139. Symptoms include ricewater stool, vomiting + symptoms of dehydration
Mechanism of vibrio cholera is just like what other bacteria?
Etec
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?
Salmonella typhi causing typoid fever
What is it called when c. diff becomes invasive
Pseudomembranous or fulminate colitis.
Which nematode/roundworm causes a raised red rash on the thighs and butt, stomach ache, GI/respiratory problems?
Strongyloides
Which nematode/roundworms infect via autoinfection?
Necator/Hookworm and Strongyloides (Nematode/roundworm)
What is the most common day care nematode/roundworm infection?
Enterobius burmicularis- pin worm
What are the two longest tapeworms we have studied?
Diphyllobothrium (fish) up to 30 ft. and Taenia (cysticercosis) up to 10 m
What are some symptoms of Schistosomiasis?
days- red itchy skin
months- fever, chills, cough, myalgia
chronic- abdominal pain, hepatomegaly, bloody stool/urine, kids (malnutrition, anemia, learning difficulties)
How do you prevent the spread of trematodes/flukes?
improve sanitation, don’t swim in contaminated water, mass admin. of praziquantel
Which nematode is associated with sheep farming and close living with dogs?
Echinococcous
What type of drug is Parmomycin and what side effects does it have?
Aminoglycoside antibiotic, SE: diarrhea
Which drug is contraindicated in Cryptosporidiosus?
Nitromidazoles
What classes of drugs are used to treat GI nematode/roundworm infections?
Benzamidazole and cholinergic antihelminths (cause paralysis- Levamasol and Pyrantel pamoate)
What is the mechanism for Benzamidazoles and describe their specificity?
Mech: bind parasite beta tubulin
Specificity: protozoa have different tubulin than eukaryokes
What is the drug of choice for tapeworms and some limitations?
Praziquantel
low efficacy against immature worms, necessitating second dose
Macrocyclic lactone binds chloride channels on nerve and muscle cells of these organisms?
Nematodes and Ascaris strongyloides
Why does macrocyclic lactone not affect human nerves and muscles?
the target chloride channels are solely located in the CNS in humans and macrocyclic lactone does not cross the BBB
what is the mechanism of action for Benzimadazoles?
Bind beta tubulin
What are the side effects of iodoquinol?
loss of visual acuity, thryoid disease cautions
