Lecture 17 Flashcards
What is the GI tract?
alimentary canal
- mouth
- pharynx (throat)
- esophagus
- stomach
- small and large intestine
What are the accessory structures to the digestive system?
- teeth and tongue
- salivary glands
- liver
- gallbladder
- pancreas
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
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
What is staphylococcal food poisoning caused by?
enterotoxin produced by Staphylococcus aureus
- serological type A: coagulates blood plasma
- can’t be killed by boiling
When are enterotoxins produced? What environment does it thrive in?
- organism is allowed to incubate in food
- high osmotic pressure and high temperature
How can we detect enterotoxins?
phage typing traces sources of contamination
What is another name for Shigellosis? What is it caused by?
bacillary dysentery
- Shigella
= facultatively anaerobic gram-negative
= 4 species
= produced by shiga toxin
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
How is shigellosis diagnosed?
antibiotic sensitivity testing
How is shigellosis treated?
fluoroquinolones + oral rehydration
What is Salmonella Gastroenteritis caused by?
salmonella enterica
- gram-negative
- facultative anaerobe
- nonendospore-forming rods
- normal in the intestinal tract
How does salmonella gastroenteritis work?
invades intestinal mucosa and multiplies
- passes through M cells and enters the lymphatics
- replicates in macrophages
What is the incubation period of salmonella gastroenteritis? What are the symptoms?
12-36 hours
- fever
- nausea
- pain
- cramps
- diarrhea
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
How is salmonella gastroenteritis diagnosed?
from the stool or by PCR
How is salmonella gastroenteritis treated?
oral hydration therapy
What is typhoid fever caused by? How is it spread?
Salmonella serotype Typhi
- spread through feces only
How does typhoid fever spread through the body?
in phagocytes
- releases organisms into the bloodstream
What are symptoms of typhoid fever?
- high fever
- headache
- intestinal wall ulceration
How can typhoid fever be treated?
- ceftriaxone
- azithromycin
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
