(10-27) Digestive System Infections Flashcards
1. List the functions of the main components of the upper digestive tract. 2. List activities of the normal flora potentially of value to the host. 3. Give the most common sources of bacteria pathogenic for the intestine. 4. List the characteristics, causes, modes of transmission, prevention and treatment for the following diseases: Cholera, Escherichia coli O157:H7, Salmonellosis, Campylobacteriosis 5. List the symptoms, causes, pathogenesis, modes of transmission, treatment, if any, and pr
What are 3 names for the passageway running from mouth to anus?
- Digestive Tract
- Alimentary Canal
- Digestive System
Which body system is a major route of microbial invasion?
The Digestive System
What are the major divisions and main purpose of the digestive system?
- Divided into upper and lower tracts
2. Main purpose to provide nutrients to body
Which areas of the digestive tract have concentrated amounts of flora, and which areas have very little?
- Flora of digestive tract mainly found in the oral cavity and intestines
- Esophagus has very little flora
- Normal stomach is devoid of microorganisms (killed by stomach acid)
Which species of bacteria is most common in the oral cavity?
Streptococcal species
How does the host limit the number of bacteria on mucus membranes within the oral cavity?
Membrane cells within the oral cavity are constantly shedding.
Which oral cavity surface is non-shedding? Explain how bacteria take advantage of that non-shedding nature?
- Teeth are nonshedding surface
2. Large numbers of bacteria can collect and form biofilm
What is the term used for the masses of bacteria that form a biofilm on non-shedding oral cavity surfaces?
dental plaque
What are the comparative amounts of bacteria in the small versus large intestine?
- Small number of bacteria colonize small intestine
2. Large intestine contains very high numbers of organisms
How many bacteria are in a gram of feces?
Approximately 100 billion
The high population of bacteria within the large intestine is due to what factor?
The abundance of nutrients in feces
Which bacteria predominate the large intestine bacterial population?
Escherichia coli and other enterobacteria
How are normal intestinal flora beneficial to humans? List 2 ways.
- They prevent pathogenic colonization of large intestine
- They synthesize many useful vitamins
~ ex. Vitamin K
Escherichia coli and other enterobacteria predominate bacterial population and are an important source of what?
Opportunistic infections, especially of the urinary tract
List 4 symptoms of bacterial diseases of the lower digestive system.
- Diarrhea
- Loss of appetite
- Nausea and vomiting
- Sometimes fever
~ Gastroenteritis
How are bacterial diseases of the lower digestive system transmitted?
Via fecal-oral route, usually ingestion of food or drinking water
Which 3 kinds of bacteria account for almost all bacterial intestinal infections?
- Vibrio species
- Camplyobacter jejuni
- Enterobacteria
What is the causative agent in Cholera?
Vibrio cholerae
Describe the bacterial attributes of Vibrio cholerae.
- Gram negative
- Curved bacillus
- Salt tolerant
What are 3 symptoms of Cholera? Elaborate.
- Classic example of severe diarrhea
~ Can amount to loss of 20 liters of fluid per day - Vomiting common in most cases
~ Usually occurs at the onset of disease - Many suffer muscles cramps
~ Caused by loss of fluid and electrolytes
Describe how Cholera infections take hold.
- Large numbers must be ingested to effect disease due to sensitivity to stomach acid
- In small intestine, organisms adhere to epithelial lining and multiply there
Describe pathogenesis of Cholera, focusing on the action of A and B toxins.
- Vibrio cholerae produces toxin
- Cholera toxin responsible for symptoms has two parts
~ B fragment has no toxicity, serves to bind toxin to cells
~ A fragment responsible for toxicity, causes excess secretion of (Cl-) fluid
How can Cholera toxin be destroyed?
By heat
What are the most common and other implemented routes of transmission for Cholera?
- Fecal contamination of water is the most common source of transmission
- Crabs and vegetable fertilized with human feces have also been implicated
How many Vibrio cholerae can a person discharge?
Person with cholera may discharge at least 1 million bacteria per milliliter of feces
What are the 2 factors that play into Cholera prevention?
Prevention depends largely on:
- Adequate sanitation
- Availability of safe water supplies
What 3 things can travels do to avoid getting Cholera?
- cook food immediately before eating
- peel fruit personally
- avoid ice, unless made with boiled water
What is the treatment for Cholera and how does it affect the mortality rate?
- Treatment depends on rapid replacement of fluids and electrolytes
- Essential before irreversible damage to vital organs
- Replacement of fluids and electrolytes decreases mortality to less than 1%
Describe the symptoms of Escherichia coli Gastroenteritis, including severity.
- Depends largely on virulence of infecting strain
- Symptoms can range from vomiting and a few loose stools to profuse water diarrhea to severe cramps and bloody diarrhea
- Fever not usually prominent
How long does recovery from Escherichia coli Gastroenteritis take?
Recovery usually occurs within 10 days
Name the 2 important virulence factors that contribute to the pathogenesis of Escherichia coli Gastroenteritis.
- Production of enterotoxin
- Adherence to cells of small intestine
~ Virulence factors foster spread
List the 4 groups that most diarrhea-causing E. coli fall into.
- Enterotoxigenic E. coli (ETEC)
- Enteroinvasive E. coli (EIEC)
- Enteropathogenic E. coli (EPEC)
- Enterohemorrhagic E. coli (EHEC)
[P.I.T.H]
Describe 3 attributes of Enterotoxigenic E. coli (ETEC).
- Most common cause of traveler’s diarrhea
- Posses adhesins that allow intestinal colonization
- Some secrete toxins (similar to cholera toxin)
Describe the damaging effect of Enteroinvasive E. coli (EIEC).
Destruction of intestinal cells leads to bloody diarrhea
Describe where Enteropathogenic E. coli (EPEC) is typically found.
Causes outbreaks in hospital nurseries and bottle fed infants in developing countries
Describe 4 attributes of Enterohemorrhagic E. coli (EHEC).
- Discovered in 1982
- Often produces severe illness due to production of potent group of toxins that interfere with protein synthesis
- Hemolytic Uremic Syndrome
~ Disseminated intravascular coagulation in kidneys - Most common strain O157:H7
In which 3 ways do Escherichia coli Gastroenteritis epidemics occur?
- Person-to-person spread
- Contaminated food and water
- Unpasteurized milk and juices
Name 3 sources of pathogenic E. coli strains.
- Humans
- Domestic animals
- Wild animals
Which are 3 preventative measures of Escherichia coli Gastroenteritis directed at?
- Hand washing
- Pasteurization of drinks
- Proper food preparation
What does treatment for Escherichia coli Gastroenteritis include?
- Replacement of fluids and electrolytes
- Infants may require antibiotics
- Traveler’s diarrhea can be controlled with bismuth preparations
~ ex. Pepto-Bismal
How do antibiotics affect Escherichia coli Gastroenteritis infections in adults?
Antibiotics tend to prolong the disease in adults
List 5 symptoms of Salmonellosis.
- Diarrhea
- Abdominal pain
- Nausea
- Vomiting
- Fever
Which 2 factors determine how much symptoms of Salmonellosis vary?
- virulence of strain
2. number of infecting organisms
What are the typical duration and severity of symptoms in a Salmonellosis infection?
Symptoms are generally short-lived and mild.
Describe the bacterial attributes of the causative agent of Salmonellosis.
- Salmonella species
- Motile
- Gram negative
- Enterobacteria
Describe the pathogenesis of Salmonellosis.
- Bacteria adhere to receptors on epithelial cells of lower small intestine
- Cells take up bacteria through phagocytosis
- Bacteria multiply within phagosome discharged through exocytosis
Which bodily fluid are Salmonella sensitive to, and what are the infective implications?
- Stomach acid
2. Large number required for infection
Why does diarrhea occur in Salmonellosis infections?
Inflammatory response increases fluid secretion resulting in diarrhea
Explain why some strains of serotype Salmonella Typhi are not easily eliminated from the body.
- Organisms cross membrane and resist killing by macrophages
- Bacteria multiply within macrophages then carried to bloodstream
- Organisms are released when macrophages die and invade tissues
- Can result in abscess, septicemia, and shock
How long can Salmonella bacteria survive in the environment?
Long periods of time.
Which demographic are commonly infected with Salmonellosis?
Children
Describe the pathogenesis of Salmonellosis.
- Bacteria adhere to receptors on epithelial cells of lower small intestine
- Cells take up bacteria through phagocytosis
- Bacteria multiply within phagosome discharged through exocytosis
Why does diarrhea occur in Salmonellosis infections?
Inflammatory response increases fluid secretion resulting in diarrhea
Explain why some strains of serotype Salmonella Typhi are not easily eliminated from the body.
- Organisms cross membrane and resist killing by macrophages
- Bacteria multiply within macrophages then carried to bloodstream
- Organisms are released when macrophages die and invade tissues
- Can result in abscess, septicemia, and shock
How long can Salmonella bacteria survive in the environment?
Long periods of time.
List 5 symptoms of Hepatitis A.
- Fatigue
- Fever
- Loss of appetite
- Nausea
- Jaundice
What are the symptoms of Hepatitis A in children less than 6 years old? What is the most common symptom?
- Nearly 70% of children less than 6 years old are asymptomatic
- Jaundice most common
How many adults with Hepatitis A require hospitalization and how long do they usually take to recover?
- 20% of adults require hospitalization
2. Full recovery in about 2 months
What was Hepatitis A formerly called?
Infectious Hepatitis
How is Hepatitis A transmitted?
Transmission is from ingestion of contaminated food or water. [The fecal-oral route.]
Describe the pathogenesis of Hepatitis A.
- Ingested virus reaches liver by unknown route
~ Liver is the main site of viral replication
~ It’s the only tissue known to be damaged - Virus is released into bile
- Virus laden bile eliminated in feces
Where do many Hepatitis A infections originate? Explain how and why it occurs.
- Many outbreaks originated from restaurants
- Due to infected food handler
- Raw shellfish frequent source of infection
What is the causative agent of Hepatitis A?
Hepatitis A virus (HAV)
Describe the viral attributes of Hepatitis A.
- Small
- Single stranded RNA genome
- Belongs to picornavirus family
- Given name hepatovirus
- Only one serotype
What are the implications of Hepatitis A only having one serotype?
- The invariability of Hep A makes it good target for vaccine.
- Vaccine available since 1995
~ It is indicated for travelers, sewer workers, and healthcare workers
What can be given to people who have been exposed to Hepatitis A, and when must it be given?
- Gamma globulin contains HAV antibody and can be given to individuals that have been exposed
- It can give short-term protection if given within 2 weeks of exposure
