Gastrointestinal System Flashcards
Name the 5 main components of the digestive system.
1) Mouth
2) Pharynx
3) Esophagus
4) Stomach
5) Small and large intestine
Name the 5 accessory structures of the GI tract.
1) Teeth and tongue
2) Salivary glands
3) Liver
4) Gallbladder
5) Pancreas
What is the typical cycle for microbial disease of the digestive system?
Fecal to oral cycle. This can be interrupted with effective sanitation.
How many tons of food pass through the GI tract in a lifetime?
25 tons
What percentage of the immune system is located in the intestinal tract? What form does it take?
80%
Gut-associated lymphoid tissue including lymph nodes and Peyer’s patches
Why are there few microorganisms in the stomach?
HCL production, very low pH
What kind of cells does the SI contain?
Paneth cells
Granule-filled phagocytic cells. Produce defensins (antibacterial protein) and lysozymes
What is the density of bacteria in the large intestine?
100 billion bacteria per gram of feces (anaerobes and facultative anaerobes)
How many different types of bacterial species are in the oral cavity?
700 different species
What are the most important types of bacteria in the oral cavity?
Streptococcus mutans is the most important cariogenic (plaque forming) organism. Gram-positive coccus, converts sucrose to lactic acid. Produces dextran, a polysaccharide that creates plaque.
Plaques attract what other carcinogenic bacteria?
Streptococci; filamentous Actinomyces
What do caries do?
Penetrate enamel into the dentin. Caused by gram positive rods and filamentous bacteria.
What happens if decay reaches the pulp?
May advance into soft tissues leading to abscess.
Gingivitis
Inflammation and infection of the gums. Caused by streptococci, actinomycetes and anaerobic gram-negative bacteria.
Periodontitis
Bone and tissue supporting the teeth are destroyed. Caused by Porphyromonas
Acute necrotizing ulcerative gingivitis (trench mouth) is caused by?
Caused by Prevotella intermedia
How do microorganisms spread in the GI tract?
Microorganisms penetrate into the small intestine and grow there or pass to other organs of the body.
How does the body respond to microorganisms in the SI?
M cells (micro fold cells) translocate antigens to the other side of the epithelium to Peyer’s patches.
What microorganisms are usually responsible for food poisoning?
Staphylococcus aureus, produces enterotoxin which is not killed by boiling. Serological type A, coagulates blood plasma.
Toxins are produced when S. aureus is allowed to incubate in food, what is this called?
Temperature abuse
Which bacteria are responsible for Bacillary Dysentery?
Genus Shigella (Shigellosis)
- Facultatively anaerobic
- gram-negative.
- Four species
- Produces Shiga toxin
What kind of dose is required to cause Shigellosis?
Small infectious dose. Attaaches to M cells, invades and spreads to other cells. Damages the intestinal wall. Can invade the bloodstream.
How is Shigellosis treated?
Fluoroquinolones and oral rehydration
What causes Salmonella?
Salmonella enterica Gram-negative Facultative anaerobe Nonendospore-forming rods Normal inhabitant of the human intestinal tract.
How does Salmonella enterica cause illness?
Invades intestinal mucosa and multiplies. Passes through M cells and enters the lymphatics. Replicates in macrophages.
What are the specifics of disease (incubation, signs and symptoms) of Salmonella?
Incubation of 12 to 36 hours.
Fever, nausea, pain and cramps, diarrhea.
What are the numbers of people affected by Salmonella?
1.4 million cases and 400 deaths annually.
What is Salmonella most associated with commercially?
Chicken and egg production as bacteria survives in the albumin.
What is typhoid fever caused by?
Salmonella typhi. Spread only by human feces. Rare in the U.S. due to sanitation.
How does Salmonella typhi bacteria spread?
Spread in phagocytes and release organisms in the bloodstream.
Signs and symptoms of typhoid fever?
High fever, headache, intestinal wall ulceration. 1-3% of patients become chronic carriers as the organism hide in the gallbladder.
How is typhoid fever treated?
Chloramphenical, quinolones or cephalosporins
What causes Cholera?
Vibrio cholerae
Slightly curved, gram-negative rod with single polar flagellum. Associated with salty waters.
How does vibrio cholera cause illness?
Produces the cholera toxin. Toxin causes the host cells to secrete electrolytes and water. Can cause a person to lose 12 to 20 litters of fluid per day. Causes shock, collapse, organ failure and death.
How is cholera treated?
IV fluid replacement, oral rehydration with electrolyte replacement (salt, sugar and water).
Noncholera vibrios
Mostly adapted to salty coastal waters. Vibrio parahaemolyticus, found in saltwater estuaries, common cause of gastroenteritis. Raw oysters and crustaceans are associated with outbreaks. Requires early antibiotic therapy.
Enteropathogenic E.coli
- Diarrhea in developing countries
- Cause the host cells to form pedestals where bacteria attach
Enteroinvasive E. coli
Causes Shigella-like dysentery
Enteroaggregative E. coli (EAEC)
Only in humans. Produces an enterotoxin causing watery diarrhea.
Enterohemorrhagic E. coli (EHEC)
Produces Shiga-like toxin. Released upon the cell’s lysis. Most outbreaks due to serotype O157:H7
EHEC what is the main reservoir and what does it cause? How is it diagnosed?
- Cattle are the main reservoir.
- Causes hemorrhagic colitis and hemolytic uremic syndrome
- Diagnosed by inability to ferment sorbitol and pulsed-field gel electrophoresis
Traveler’s diarrhea causes and treatment?
- Most common cause is Enterotoxigenic Eschericia coli (ETEC)
- Second most common is EAEC Enteroaggregative E. coli
- Can also be caused by Salmonella, Shigella and Campylobacter
- Treatment with oral rehydration therapy and bismuth-containing preparations
Campylobacter gastroenteritis cause
- Caused by campylobacter jejuni (gram-negative, microaerophilic, spirally curved bacteria)
Where is campylobacter jejune found?
- Common in the intestines of poultry
- 60% of cattle excrete this organism in their feces and milk
What are the signs and symptoms of campylobecter gastroenteritis?
Fever, cramping, abdominal pain, diarrhea, dysentery
1 in 1000 cases of campylobacter lead to ….
Guillain-Barre syndrome
Peptic ulcer disease is caused by…
Helicobacter pylori
Infects 30-50% of the population in developed world.
How does helicobacter pylori survive in the stomach?
Grows in stomach acid by producing urease, converts urea into alkaline ammonia
How are peptic ulcers treated?
Treated with antimicrobial drugs and bismuth subsalicylate
What causes Yersinia gastroenteritis?
Yersinia enterocolitica and yersinia pseudotuberculosis
- gram-negative
- inhabits animals, transmitted in meat and milk
- grows at 4 degrees C
Signs and symptoms of Yersinia gastroenteritis? Treatment?
Diarrhea, fever, headache, abdominal pain (often misdiagnosed as appendicitis). Treated with antibiotics and oral rehydration.
Clostridium perfringens gastroenteritis
Gram-positive Endospore forming Obligately anaerobic rod Illness caused by exotoxin Also causes gas gangrene Symptoms mild, 8-12 hours after eating
Clostridium difficile associated diarrhea details, why so important?
Gram-positive
Endospore forming
Anaerobe
Causes MORE deaths than all other intestinal infections combined, mostly in health care settings.
How does Clostridium difficile cause death?
Creates life-threatening colitis through ulceration and perforation of the intestinal wall. Precipitated by extended use of antibiotics which eliminate competing normal intestinal bacteria.
Discuss bacillus cereus gastroenteritis.
- Large, gram-positive, endospore forming
- Common in soil and vegetation
- Spores survive heating, germinate and produce toxins
What does the mumps virus do?
Targets parotid glands causing painful swelling for 16 to 18 days after exposure.
How is the mumps virus transmitted?
It is transmitted in the saliva and respiratory secretions. It multiplies in the respiratory tract and reaches the salivary glands via the bloodstream. It may cause orchitis, meningitis, ovary inflammation and pancreatitis
What is hepatitis?
Inflammation of the liver. May result from drug or chemical toxicity, Epstein-Barr virus, cytomegalovirus, or hepatitis viruses
Hepatitis A virus characteristics
- Single-stranded RNA; lacks an envelope.
- Entry via the oral route, multiplies in the epithelial lining of the intestinal tract
- Spreads to the liver, kidneys and spleen
Signs and symptoms of hep A
- Anorexia, malaise, nausea, diarrhea, fever, chills
- Later jaundice and dark urine
- Symptoms last 2 to 21 days; low mortality
How is Hep A detected and treated?
- Detected via IgM anti-HAV
- Treated with immunoglobulin
- Inactivated vaccine for prevention
Hepatitis B virus characteristics
- Double-stranded DNA; enveloped
- Resembles retroviruses
How is Hep B transmitted?
Via blood and bodily fluids, up to 1 billion viruses per ml of blood. Contain complete visions (Dane particle)
Hepatits B is detected as…
Spherical particles and filamentous particles that lack DNA and contain hep B surface antigen
Acute hep B
- Often subclinical
- Similar symptoms to hep A, gradual recovery
- Fulminant in 1% of cases leading to sudden massive liver damage that can be fatal
Chronic hep B
HBeAg
- Involves 10% of infected patients
- May lead to liver cirrhosis or liver cancer
- Presence of HBeAg indicates a vigorously replicating virus
- Treated with interferons and nucleoside analogs
Hepatitis C virus characterisitcs
- Single-stranded RNA; enveloped
- Often transfusion-transmitted
- Destroys the liver by using genetic variation to evade the immune response
What kills more people in the U.S., AIDS or Hep C?
Hep C
How many cases of Hep C become chronic?
85%
25% develop liver cirrhosis or cancer
How is Hep C treated?
Peginterferon and ribavirin. There is no vaccine
Hepatitis D
- Acute (coinfection) and chronic (superinfection) forms
- Linked to hepatitis B infection
Hepatitis E
- Spread by fecal-oral transmission, similar to Hep a
- Endemic in areas with poor sanitation
Amebic Dysentery (Amebiasis) is caused by? How does it cause illness?
- Entamoeba histolytica
- Produces cysts that survive stomach acid
- Trophozoites produced from cysts in the intestines, these multiply in the wall of the large intestine, perforate and cause abscesses.
EXAM: What is a clue that differentiates amebic dysentery from other types of dysentery we have discussed?
There is blood in the feces in addition to mucus
How is amebiasis detected?
Treated?
- Detection with latex agglutination and FA tests
- Treated with metronidazole plus iodoquinol
Beef tapeworm
Taenia saginata
Pork tapeworm
Taenia solium
Fish tapeworm
Diphyllobothrium latum
Taeniasis
adult tapeworm infects the intestine
Cysticercosis
infection with the larval stage by ingesting eggs
Opthalmic cysticercosis
larvae lodge in the ey
Neurocysticercosis
larvae develop in the central nervous system
What is the three-stage life cycle of tapeworms?
1) Eggs are excreted in the feces and ingested by animals
2) Eggs hatch into a larval cysticercus that lodges in the muscle
3) Human ingests undercooked meat containing cysticerci which develop into adult tapeworms in the intestine
How is taeniasis diagnosed
Diagnosed with eggs or worm segments in the feces
How is tapeworm infection treated?
Praziquantel and albendazole
Hydatid disease caused by?
Caused by tapeworm Echinococcus granulosus
How does the Echinococcus granulosus tapeworm cause disease? How is it diagnosed? Treated?
- Eggs are ingested and migrate to liver, lungs or brain and develop into a cyst that can grow and hold up to 15 litters of fluid. If it ruptures it may cause anaphylactic shock.
- Diagnosed with serological tests, X rays, CT and MRI
- Treated with surgical removal or albendazole
Enterobius vermicularis
Pinworm, a tiny nematode, lays eggs around the anus causing local itching
How are pinworms treated?
Pyrantel pamoate and mebendazole
Name some hookworms
Necator americanus
Ancylostoma duodenale
How do hookworms cause illness? What are the symptoms?
- Attach to the intestinal wall and feeds on blood and tissue
- Causes anemia, lethargic behaviour and pica
How do hookworms infect people?
Carried from human feces in soil that contacts bare skin
EXAM: Ascariasis, cause and how common?
- Caused by nematode Ascaris lumbricoides
- 30% of the worldwide population is infected.
What is the cycle of ascariasis?
- Eggs shed in feces and ingested by another person
- Hatch into larvae and pass into the bloodstream and lungs
- Larvae migrate to the throat and are swallowed
- Larvae develop into adult worms in the intestinal tract and emerge from anus, mouth or nose
Ascariasis treatment?
Treated with mebendazole or albendazole
Whipworm (trichuris trichiura)
Size, cycle
- 30 to 50mm in length
- Distribution similar to A. lumbricoides
- Eggs are ingested and enter intestinal glands
- Eggs hatch and grow on the intestinal surface
- Adult worm buries into the intestinal mucosa and live as a parasite feeding on cell contents and blood
What kind of symptoms do whipworms cause?
Anemia, malnutrition, retarded growth.
Trichinellosis caused by? How does it infect people?
Trichinella spiralis
- Encysted larvae are ingested from undercooked pork and other meats
- Digestion removes the cyst wall and the worm matures into an adult
- Adults produce larvae in the intestines that invade tissues and for knew cysts
What symptoms do trichinellosis cause?
Fever, eye swelling, GI upset
Rotavirus
- Common in children; low mortality
- 2 to 3 day incubation; low grade fever, diarrhea, vomiting
- Prevented with live oral vaccine
Norovirus
- Caliciviruses
- Fecal-oral transmission
- Low infectious dose
- 18 to 48 hour incubation; diarrhea and vomiting
- Detected with PCR and EIA tests
What can mycotoxins (produced by fungi) cause?
1) Blood diseases
2) Nervous system disorders
3) Kidney damage
4) Liver damage
5) Cancer
What is ergot poisoning caused by and what does it do?
Mycotoxins produced by Claviceps purpurea.
- Occurs in grains
- Restricts blood flow (gangrene) and causes hallucinations.
What is the cause of aflatoxin poisoning and what does it do?
Mycotoxins produced by Aspergillus flavus.
- Likely to be found on peanuts
- Causes liver cirrhosis and liver cancer
What is giardiasis caused by?
Caused by Giardia intestinalis, a flagellated protozoan. It forms cysts in feces and water which become active trophozoites in the body. These attach to the intestinal wall with suckers.
What are the signs and symptoms of giardia?
Prolonged diarrhea Malaise Weight loss Flatulence Cramps Hydrogen sulphide can be detected on the breath or in the stool.
How is giardia diagnosed and treated?
String test, ELISA, or FA.
Treated with metronidazole and nitazoxanide
What is cryptosporidiosis caused by and what does it do?
- -> Caused by Cryptosporidium parvum and C. hominid.
- -> Transmitted through drinking water
- -> Ingested oocysts release sporozoites.
- -> Cholera-like diarrhea for 10-14 days
Cyclospora diarrheal infection is caused by? Treatment?
Parasite Cyclospora cayetanensis from feces contaminated water. Causes days or weeks of watery diarrhea. Treated with trimethoprim and sulfamethoxazole.
