Lecture 17 Flashcards by Joanne Huynh

What is the GI tract?

alimentary canal
- mouth
- pharynx (throat)
- esophagus
- stomach
- small and large intestine

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What are the accessory structures to the digestive system?

teeth and tongue
salivary glands
liver
gallbladder
pancreas

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How much of the immune system is in the intestinal tract? What is the tissue called?

70%
- Gut-associated lymphoid tissue (GALT)
- lymph nodes
- Peyer’s patches

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What are some examples of normal microbiota in the digestive system?

millions of bacteria in saliva
few microorganisms in the stomach (high acidity)
paneth cells in small intestines (granule-filled phagocytic cells that produce defensins)
aerobes and facultative anaerobes in large intestine
100 billion bacteria in feces

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What is staphylococcal food poisoning caused by?

enterotoxin produced by Staphylococcus aureus
- serological type A: coagulates blood plasma
- can’t be killed by boiling

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When are enterotoxins produced? What environment does it thrive in?

organism is allowed to incubate in food
high osmotic pressure and high temperature

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How can we detect enterotoxins?

phage typing traces sources of contamination

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What is another name for Shigellosis? What is it caused by?

bacillary dysentery
- Shigella
= facultatively anaerobic gram-negative
= 4 species
= produced by shiga toxin

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How can shigellosis be spread?

small infectious dose
- attaches to M cells, invades via micropinocytosis and spreads to other cells
- damages intestinal wall
- can invade bloodstream

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How is shigellosis diagnosed?

antibiotic sensitivity testing

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How is shigellosis treated?

fluoroquinolones + oral rehydration

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What is Salmonella Gastroenteritis caused by?

salmonella enterica
- gram-negative
- facultative anaerobe
- nonendospore-forming rods
- normal in the intestinal tract

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How does salmonella gastroenteritis work?

invades intestinal mucosa and multiplies
- passes through M cells and enters the lymphatics
- replicates in macrophages

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What is the incubation period of salmonella gastroenteritis? What are the symptoms?

12-36 hours
- fever
- nausea
- pain
- cramps
- diarrhea

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What is salmonella gastroenteritis associated with? How many cases annually?

commercial chicken and egg production (bacteria survive in the albumin)
- 1 million cases & 380 deaths annually

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How is salmonella gastroenteritis diagnosed?

from the stool or by PCR

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How is salmonella gastroenteritis treated?

oral hydration therapy

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What is typhoid fever caused by? How is it spread?

Salmonella serotype Typhi
- spread through feces only

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How does typhoid fever spread through the body?

in phagocytes
- releases organisms into the bloodstream

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What are symptoms of typhoid fever?

high fever
headache
intestinal wall ulceration

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How can typhoid fever be treated?

ceftriaxone
azithromycin

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What is cholera caused by? What is its characteristics?

Vibrio cholerae
- slightly curved gram-negative rod with single polar flagellum

What does Vibrio cholera produce? What is its purpose?

makes cholera toxin
- causes host cell to secrete electrolytes and water
- causes rice water stools

What is the treatment of cholera?

IV fluid replacement

How does incidence of cholera change after natural disasters?

cholera increases when sanitation and sewage disposal systems are compromised

How can you prepare for natural disasters?

- prepare oral rehydration solutions - stockpile vaccines - proper sanitation - water storage - handwashing

What are the 5 types of E. coli?

- enteropathogenic E. coli (EPEC) - Enteroinvasive E. coli (EIEC) - enteroaggregative E. coli (EAEC) - enterohemorrhagic E. coli (EHEC) - enterotoxigenic E. coli (ETEC)

What are the characteristics of EPEC?

diarrhea in developing countries - causes host cells to form pedestals where the bacteria attaches

What are the characteristics of EIEC?

causes shigella-like dysentery

What are the characteristics of EAEC?

only in humans - produces enterotoxin causing watery diarrhea

What are the characteristics of EHEC?

- produces shiga-like toxin - cattle = main reservoir - causes hemorrhagic colitis and hemolytic uremic syndrome

How is EHEC diagnosed?

inability to ferment sorbitol - ELISA test

What is the cause of traveler's diarrhea?

ETEC - salmonella - shigella - campylobacter

How is traveler's diarrhea treated?

- oral rehydration therapy - bismuth-containing preparations - antidiarrheal medications

What is the characteristic of Clostridium difficile-associated diarrhea?

- gram-positive, endospore-forming anaerobe - causes more deaths than all other intestinal infections combined

What happens in life-threatening colitis?

ulceration and perforation of the intestinal wall

What causes Giardiasis? What is the characteristic of it?

giardia intestinalis - flagellated protozoan - forms cysts in feces and water; trophozoites in the body - attaches to the intestinal wall

What are the symptoms of giardiasis?

- prolonged diarrhea - malaise - weight loss - flatulence - cramps - hydrogen sulfide in the breath or stools

How can giardiasis be diagnosed?

- microscopic examination of stool samples - serological fecal tests

How can giardiasis be treated?

metronidazole and nitazoxanide

What is Amebiasis caused by? What does the bacteria cause?

entamoeba histolytica - produces cysts that survive stomach acid - trophozoites produced form cysts in the intestines - multiply in the wall of the large intestine

What are symptoms of amebiasis?

- blood and mucus in feces - can perforate intestinal wall, causing abscesses - organisms invade liver

How can amebiasis be detected and treated?

serological EIA tests - treat with metronidazole

What is beef tapeworm caused by?

taenia saginata

What is pork tapeworm caused by?

taenia solium

What is fish tapeworm caused by?

diphyllobthrium latum

What is taeniasis?

adult tapeworm infects intestines

What is cysticercosis?

infection with larval stage by ingesting eggs

What is ophthalmic cysticercosis?

larvae lodge in the eye

What is neurocysticercosis?

larvae develop in the CNS

What is the 3-stage life cycle of the tapeworm?

1) eggs excreted in feces and ingested by animals 2) eggs hatch into larval cysticercus that lodges in muscle 3) human ingests undercooked meet with cysticerci and develops into adult tapeworms in the intestine

How can tapeworms be diagnosed?

eggs or segments in the feces

How can tapeworms be treated?

praziquantel and niclosamide