List the parts of the digestive system.
Mouth, pharynx, esophagus, stomach, small intestine, large intestine,
rectum, anus.
Accessory structures: teeth, tongue, salivary glands, liver,
gallbladder, pancreas.
What is Gut-Associated Lymphoid Tissue (GALT)?
Loosely organized lymphoid tissue and structures of the intestinal
tract where 80% of the immune system is located. Found in lymph nodes
and Peyer's patches.
Paneth Cells
Granule-filled phagocytic cells (found in small intestines) that are
part of antimicrobial defenses.
They phagocytize bacteria and produce antibacterial proteins
called defensins and lysozyme.
Dental plaque
a biofilm on teeth made of microbes and their products; involved in
formation of dental caries.
Dental caries
AKA: Tooth decay.
Pathogen: usually Streptococcus mutans.
Symptoms: discoloration or hole in tooth enamel.
Treatment: Remove decayed area.
Prevention: brushing, flossing, reducing dietary sucrose (glucose
+ fructose)
Other issues: plaques attract other cariogenic bacteria, such as
the filamentous Actinomyces
How does dental caries actually happen?
Caries penetrate from enamel to dentin as a result of gram + rods and
filamentous bacteria.
The decay can reach the pulp, which contains blood supply and
nerves --> may advance to soft tissues and cause abscesses.
Peridontal disease
Term for number of conditions characterized by inflammation and
degeneration of structures that support the teeth.
Caused by various pathogens, depending on specific type.
Includes: 1) Gingivitis, 2) Peridontitis, and 3) Acute necrotizing
ulcerative gingivitis (trench mouth)
Symptoms: bleeding gums, pus pockets.
Treatment: remove damaged area; antibiotics
Prevention: plaque removal
Gingivitis
Inflammation and infection of the gums, characterized by bleeding of
the gums during teeth brushing.
Caused by Streptococci, Actinomycetes, and anaerobic gram - bacteria.
Peridontitis
Gingivitis that progresses to a chronic condition in which bone and
supporting dental tissue are destroyed.
Caused by Porphyromonas
Acute Necrotizing Ulcerative Gingivitis
(AKA Vincent's Disease or trench mouth)
Primary pathogen: Prevotella intermedia
Symptoms: pain chewing, halitosis
Treatment: Remove damaged area, give Metronidazole
Prevention: brushing, flossing
Two categories of disease:
1) Infection
2) Intoxication
What is infection?
When a pathogen enters the GI tract and multiplies. Pathogen can
enter penetrate the intestinal mucosa and grow there OR pass to other
systemic organs.
Characterized by delay in appearance of GI disturbance while
pathogen multiplies. Usually have fever in response to pathogen.
What is Intoxication?
When pathogens cause disease by forming toxins that affect the GI
tract. Caused by the ingestion of such a preformed toxin.
Usually see a very sudden appearance of symptoms. Rarely see fever.
Dysentery
Any time severe diarrhea is accompanied by blood or mucus.
Gastroenteritis
Disease causing inflammation of the stomach and intestinal mucosa.
Leading cause: Staphylococcal food poisoning via S. aureus
enterotoxin ingestion.
Staphylococcal Food Poisoning
Pathogen: Staphylococcal aureus
Symptoms: nausea, vomitting, diarrhea
Intoxication or infection: Intoxication of enterotoxin
Diagnostic Test: Phage Typinga
How does one ingest the enterotoxin responsible for Staphylococcal
food poisoning?
The toxin is produced when the organism is allowed to incubate in
food (temperature abuse). It is not killed by boiling bc it withstands
high temperature and high osmotic pressure. It is also serological
type A (coagulates blood plasma)
Again, reheating will not eliminate the toxin--only the bacteria itself.
Shigellosis (Bacterial Dysentery)
Pathogen: Shigella spp (Facultative anaerobe, gram -)
Symptoms: tissue damage, severe diarrhea, abdominal cramps, fever
Intoxication or infection: Both--infection + endotoxin, exotoxin,
and Shiga toxin
Diagnostic test: isolation of bacteria on selective media
Treatment: Fluoroquinolones and oral rehydration
Transmission: only person to person
Chiefly affects kids under 5 YOA
How does Shigellosis happen?
1) Shigell enters epithelial cell in intestinal tract lining (via
membrane ruffling)
2) Multiplies inside cell
3) Shigella invades neighboring epithelial cells, avoiding immune defenses
4) An abscess forms as epithelial cells are killed by infection.
Bacteria rarely spread to bloodstream
Salmonellosis
Pathogen: Salmonella enterica (gram -, facultative anaerobe, normal
inhabitant of GI tract)
Symptoms: fever, nausea and diarrhea, cramps, abdominal pain
(incubation of 12-36 hours)
Intoxication or infection: infection + endotoxin
Diagnostic test: isolation of bacteria on selective media,
serotyping; usually diagnosed direclty from the stool or by PCR
Treatment: oral rehydration
How does S. enterica cause Salmonellosis?
It invades intestinal mucosa and multiplies. It passes through M
cells and enters the lymphatics to replicate in macrophages.
It is associated with commercial chicken and egg production
(bacteria survive in the albumin)
Typhoid fever
Pathogen: Salmonella typhi
Spread only by human feces (rare in US due to sanitation).
Significant mortality
Symptoms: high fever, headache, intestinal wall ulceration
Intoxication or infection: Infection + endotoxin
Diagnostic test: isolation of bacteria on selective media, serotyping
Treatment: Chloramphenicol, quinolones, or cephalosporins
*Note: 1-3% of patients become chronic carries by harboring
organism in gallbladder
How is typhoid fever spread?
Bacteria spread throughout body in phagocytes, releasing organisms
into the bloodstream
Cholera
Pathogen: Vibrio cholerae (gram - rod with single flagellum,
associated with salty waters)
Symptoms: diarrhea with large water loss ("rice water
stools")--can lose 12-20 liters of fluid per day --> shock,
collapse, organ failure, and possible death
Treatment: rehydration (IV fluid replacement), and doxycycline
Why is Vibrio cholerae so damaging?
It produces the cholera toxin, which causes host cells to secrete
electrolytes and water --> causes rice water stools.
Also, it increases when sanitation and sewage disposal systems are
compromised--like after natural disasters (e.g Haiti outbreak after earthquake)
Disaster preparedness to prevent cholera after natural disasters
Oral rehydration solutions (salt, sugar, water)
Stockpiling vaccines
Ultimate solution: proper sanitation, water storage, handwashing
Noncholera Vibrios
*Adapted to salty coastal waters (e.g. Parahaemolyticus)
Require early antibiotic therapy
Escherichia coli Gastroenteritis
Pathogen: EPEC (Enteropathogenic), EIEC (Enteroinvasive), EAEC
(Enteroaggregative), and ETEC
Symptoms: diarrhea
Treatment: oral rehydration
Where is Enteropathogenic E Coli (EPEC) most seen? How does it wreak havoc?
In developing countries.
By causing host cells to form pedestals where bacteria attach
What kind of toxin does Enteroinvasive E. coli (EIEC) produce?
Shiga-like toxin, which is released upon host cell lysis. -->
causes hemorrhagic colitis and hemolytic uremic syndrome.
This is why is produces a Shigella-like dysentery.
Most outbreaks are due to serotype O157.H7.
Diagnosed by inability to ferment sorbitol and pulsed-field gel electrophoresis.
What kind of toxin does Enteroaggregative E. coli (EAEC) produce?
An enterotoxin that causes watery diarrhea.
It is only in humans.
Traveler's Diarrhea
Pathogen: most common cause is ETEC, 2nd most common is EAEC. (Also
caused by Salmonella, Shigella, and Campylobacter)
Treatment: oral rehydration therapy and bismuth-containing preparations
Campylobacter Gastroenteritis
Pathogen: Campylobacter jejuni (gram -, microaerophilic, spirally curved)
*leading cause of foodborne illness in US (common in poultry
intestines; 60% of cattle excrete organism in feces and milk)
Symptoms: fever, abdominal pain, diarrhea, dysentery; 1/1000 cases
--> Guillain-Barre syndrome
Infection or intoxication: infection
Treatment: none.
Helicobacter Peptic Ulcer Disease
Pathogen: Helicobacter pylori (infects 30-50% of population in
developed world)
Grows in stomach acid by producing urease, which converts urea to
alkaline ammonia --> disrupts stomach mucosa and causes inflammation
Symptoms: peptic ulcers
Treatment: antimicrobial drugs and bismuth subsalicylate
Diagnostic test: biopsy, culture, and urea breath test.
Yersinia Gastroenteritis
Pathogen: Yersinia enterocolitica and Yersinia pseudotuberculosis
(gram -, inhabits animals, transmitted in meat and milk, grows at 4
deg C)
Symptoms: Diarrhea, fever, headache, abdominal pain.
**Often misdiagnosed as appendicitis
Treatment: antibiotics and oral rehydration
Clostridium perfringens Gastroenteritis
Pathogen: C. perfringens (gram +, endospore forming, obligate
anaerobic rod)
*Assoc. w/foods containing animal intestinal contents (creates low
O2 level and produces exotoxin)
Symptoms: usually limited to diarrhea, but can cause gas gangrene
(usually mild symptoms that start 8-12 hrs after ingestion)
Treatment: oral rehydration
Clostridium difficile Associated Diarrhea
Pathogen: C. difficile (gram +, endospore-forming anaerobe)
Symptoms: mild diarrhea to colitis
Diagnostic test: cytotoxin assay
Treatment: Metronidazole, vancomycin
Is C. difficile-associated diarrhea life threatening?
Yes, it can be. It causes more deaths than all other intestinal
infections combined, mostly in health care settings.
The colitis it sometimes causes can be especially life threatening
as it can involve ulceration and perforation of the intestinal wall.
What is C. difficile associated diarrhea usually precipitated by?
Extended antibiotic use, which eliminates competing intestinal bacteria.
Bacillus cereus Gastroenteritis
Pathogen: B. cereus (large, gram +, endospore forming) *common in
soil and vegetation; spores survive heating, germinate, and produce
toxins--diff toxins cause diff symptoms.
Symptoms: may take form of diarrhea, nausea, vomiting
Intoxication or infection: intoxication
Treatment: none.
Mumps Virus
Pathogen: Paramyxovirus
Symptoms: painful swelling of parotid glands. May cause orchitis
(swelling of testes), meningitis, ovary inflammation, or pancreatitis.
Incubation: 16-18 days
Transmission: via saliva and respiratory secretions (multiples in
respiratory tract and reaches salivary glands via bloodstream)
Prevention: MMR vaccine
Hepatitis
Inflammation of the liver.
Causes: drug or chemical toxicity, Epstein-Barr Virus (EBV),
cytomegalovirus (CMV), or the hepatitis viruses
Hepatitis A
Pathogen: Hepatitis A Virus (HAV), Piconaviridae (Single stranded RNA
virus w/o envelope)
Entry: via oral route; multiplies in epithelial lining of
intestinal tract before spreading to liver, kidneys, and spleen
Symptoms: mostly subliclinical; fever, anorexia, malaise, nausea,
diarrhea, chills. In severe cases, eventually jaundice and dark urine.
Last 2-21 days; low mortality. NO chronic disease.
Diagnostic test: IgM anti-HAV antibodies
Treatment: immunoglobulins
Prevention: Inactivated virus vaccine
Hepatitis B
Pathogen: Hepatitis B Virus (HBV), Hepadnaviridae (double stranded
DNA virus, enveloped--resembles retroviruses)
Transmission: via blood and bodily fluids (parenteral and sexual contact)
Symptoms: like HAV, but w/o headache and more likely to progress
to severe liver damage and can be chronic dz that leads to liver
cirrhosis or liver cancer.
Incubation: 4-26 weeks
Diagnostic: IgM antibodies + viral components (can find Complete
virions called Dane particles, as well as spherical and filamentous
particles lacking DNA but containing HH surface Antigen called HBsAG)
Treatment: Hepatitis B immunoglobulin. For chronic dz, treat
w/interferons and nucleoside analogs.
Prevention: vaccine (genetically modified vaccine produced in yeast)
Hepatitis C
Pathogen: Hepatits C Virus (HCV) (Single stranded RNA enveloped), Flaviviridae
Transmission: Parenteral (often transfusion transmitted)
Symptoms: similar to HBV, more likely to become chronic
Treatment: Peginterferon and Ribavirin
No vaccine.
How does HCV evade immune response?
It uses genetic variation to evade immune response and destroy the
liver. This is why 85% cases become chronic, with 25% developing liver
cirrhosis or cancer.
It kills more in the US than AIDS.
Hepatitis D
Pathogen: Hepatitis D Virus (HDV), Deltaviridae
Transmission: Parenteral; REQUIRES co-infection with HBV.
Acute (coinfection) and chronic (superinfection) forms.
HBV vaccine is protective.
Hepatits E
Pathogen: Hepatitis E Virus, Calciviridae
Transmissoin: Fecal-oral (endemic in areas w/poor sanitation)
Symptoms: Similar to HAV, but with especially high mortality in
pregnant women.
HAV vaccine is protective.
Viral Gastroenteritis
Can be caused by: 1) Rotavirus or 2) Norovirus
Viral Gastroenteritis: Rotavirus
Pathogen: Rotavirus
Incubation: 2-3 days
Symptoms: low grade fever, diarrhea, vomiting
Common in children, low mortality
Detection: EIA test
Prevention: live oral vaccine
Treatment: oral rehydration
Viral Gastroenteritis: Norovirus
Pathogen: Calciviruses
Transmission: Fecal-oral (low infectious dose)
Incubation: 18-48 hrs
Symptoms: diarrhea and vomiting
Detection: PCR and EIA tests
Mycotoxins
Toxins produced by fungi that can cause blood diseases, nervous
system disorders, kidney damage, liver damage, and cancer.
Ergot poisoning
Causative agent: mycotoxins produced by Clavipeps purpurea
Symptoms: Restricted blood flow to limbs (gangrene) and hallucinations
Reservoir: fungus growing on grains
Treatment: none
Alfatoxin poisoning
Causative agent: mycotoxins produced by Aspergillus flavus
Symptoms: liver cirrhosis or liver cancer
Reservoir: fungus growing on food, esp peanuts
Treatment: none
Giardiasis
Pathogen: Giardia intestinalis
Symptoms: Protozoan adheres to intestinal wall, which may inhibit
nutritional absorption and cause diarrhea --> prolonged diarrhea,
malaise, weight loss, flatulence, cramps, hydrogen sulfide detected in
breath or stools
Reservoir: water, feces (forms cysts in feces and water,
trophozoites in body)
Diagnosis: String test, ELISA, or FA test
Treatment: Metronidazole and nitazoxanide
Cryptosporidosis
Pathogen: Cryptosporidium parvum and C. hominis (ingested oocysts
release sporozoites which invade intestinal epithelium)
Transmission: drinking water (resistant to chlorination)
Symptoms: Cholera-like Diarrhea for 10-14 days, life threatening in
immunocompromised patients
Reservoir: cattle, water.
Diagnosis: FA test or immunoassay
Treatment: Nitazoxanide
Cyclospora Diarrheal Infection
Pathogen: Cyclospora cayetanensis
Symptoms: days or weeks of watery diarrhea (caused by oocysts
ingested from drinking water contaminated with feces)
No satisfactory diagnostic tests
Treatment: Trimethoprim and Sulfamethoxazole
Amebic dystenery (Amebiasis)
Pathogen: Entamoeba histolytica (produces cysts that survive stomach
acid; trophozoites produced from cysts in intestines multiple in wall
of large intestine)
Symptoms: Amoeba lyses epithelial cells of intestine and perforate
intestinal wall, causing abscesses --> significant mortality rate.
Detection: latex agglutination or FA tests
Treatment: metronidazole + Iodoquinol
Tapeworms
3 major types:
Beef tapeworm: Taenia saginata
Pork tapeworm: Taenia solium
Fish tapework: Diphyllobothrium latum
Diagnosis: eggs or segments in feces
Treatment: Praziquantel and Albendazole
Taeniasis
adult tapeworm infection of intestines
Cysticercosis
Tapeworm infection from larval stage by infecting eggs
Ophthalmic Cysticercosis
Tapeworm infection when larvae lodge in the eye
Neurocysticercosis
Tapeworm infection when larvae develop in central nervous system
Describe the 3-stage life cycle of a tapeworm
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 intestines
Hydatid Disease
Pathogen: Echinococcus granulosus
Symptoms: Eggs are ingested and migrate to liver, lungs, or
brain--> Develop into HYDATID CYST that can grow and hold 15 L
fluid --> may rupture and cause anaphylactic shock
Diagnosis: serological tests, X rays, CT or MRI
Treatment: Surgical removal or Albendazole
Pinworms
Pathogen: Enterobius vermicularis (tiny nematode)
Symptoms: local itching around anus (from nematode laying eggs)
Diagnostic: microscopic exam
Treatment: Pyrantel Pamoate and Mebendazole
Hookworms
Pathogen: Necator americanus and Ancylostoma duodenale (nematodes)
--> attach to intestinal wall and feed on blood and tissue
Symptoms: anemia, lethargic behavior,and craving for peculiar foods (pica)
Carried from human feces in soil that contact bare skin
Treatment: Mebendazole
Ascariasis
Pathogen: Ascaris lumbricoies (nematode)
Symptoms: Few (nematodes live off undigested intestinal contents)
Treatment: Mebendazole or Albendazole
30% of world population is infected.
How is Ascariasis transmitted?
1)Eggs shed in the feces and are ingested by another person.
2)Eggs hatch into larvae and pass into bloodstream and lungs.
3)Larvae migrate to throat and are swallowed.
4) They develop into adult worms in the intestinal tract and emerge
from anus, mouth, or nose.
Whipworm
Pathogen: Trichuris trichiuria
Symptoms: Anemia, malnutrition, and retarded growth
Treatment: Mebendazole or Albendazole
How is Whipworm transmitted?
1) Eggs are ingested and enter the intestinal glands
2) Eggs hatch and grow on intestinal surface
3) Adult worm buries into the intestinal mucosa and lives as a
parasite, feeding on cell contents and blood
Trichinellosis
Pathogen: Trichinella spiralis
Symptoms: fever, eye swelling, GI upset
Treatment: Mebendazole or Albendazole
How is Trichinellosis transmitted?
1) Encysted larvae are ingested from undercooked pork and other meats.
2) Digestion removes the cyst wall and the worm matures into an adult
3) Adults produce larvae in the intestines that invade tissues and
form new cysts
Bacterial diseases of the mouth
Dental caries, plaque, tartar, peridontal disease, gingivitis, peridontitis
dental plaque
accumulation of microbes and their products on teeth
dental tartar
calcified plaque
Bacterial diseases of the lower digestive system
1) staphylococcal food poisoning
2) salmonellosis
3) typhoid fever
4) shigellosis
5) cholera
6) E. coli gastroenteritis
7) Bacterial gastroenteritis
8) ulcers
9) C. difficile
Enterotoxin
Exotoxin in the digestive system; survives 30 min of boiling.
Causes of bacterial gastroenteritis
1) Campylobacteria
2) Yersenia
3) Clostridium perfringens
4) Bacillus cereus
Viral diseases of the digestive system
Mumps, hepatitis, viral gastroenteritis
Viral gastroenteritis causes
90% rotavirus or norovirus (calciviruses)
Protozoan diseases of GI system
1) Giardiasis
2) Cryptosporidiosis
3) Cyclospora
4) Amebic dysentery
Why can Helicobacter survive in gastric juice?
It neutralizes acid by making an enzyme
T/F: Clostridium and Bacillus are endospore forming bacteria that
cause gastroenteritis.
True.
3 viruses responsible for inflammation of the liver.
1) Hep C
2) Hep B
3) Cyomegalovirus
Most of the normal microbiota of the digestive system are found in the
small and large intestines
Dental plaque is an example of ____
a biofilm
Which is the correct sequence of events regarding the stages of tooth
decay? 1. Dentin decay 2. Enamel decay 3. Plaque 4. Pulp decay
3,2,1,4 (Plaque > Enamel decay > Dentin decay > Pulp decay)
Which of the following statements about salmonellosis is
FALSE?- A healthy carrier state exists. - Severity of
disease depends on number of organisms ingested. - It is often
associated with poultry products. -The mortality rate is high.
- It is a bacterial infection
The mortality rate is high
Poultry products are a likely source of infection by_____.
Salmonella enterica.
The most common cause of traveler's diarrhea is __.
E. coli.
Helicobacter pylori can grow in the stomach because it ____.
possesses an enzyme that neutralizes HCl.
A patient exhibits hemorrhagic colitis and is treated via intravenous
rehydration. The pathogen is a gram-negative rod. It is isolated and
differentiated from related organisms based on its inability to
ferment sorbitol. What is a likely diagnosis?
E. Coli Gastroenteritis
Rice water stools" are characteristic of ____.
Cholera.
Which of the following statements about staphylococcal food poisoning
is FALSE?-It is characterized by rapid onset and short duration
of symptoms. - It is caused by ingesting an enterotoxin. -
It can be prevented by adequate refrigeration of food. -It is
treated by replacing water and electrolytes. -It can be
prevented by heating foods to 50�C for 15 minutes.
It can be prevented by heating foods to 50�C for 15 minutes.
Which of the following NOT true for both hepatitis B and hepatitis C
infection? The virus can cause a chronic disease. The
infection is transmitted through blood and body fluids.
The disease is prevented by vaccination.
Diagnosis can be achieved through testing the blood for antibodies.
The disease is prevented by vaccination.
What do hepatitis A and hepatitis B have in common?
Both can be prevented by a vaccine.
John went to a picnic. He took some leftover chicken and rice home,
heated it on the stove, ate it, and got sick two hours later. John
thought the heating made his food safe because it would have killed
any bacteria present. He didn't know that __________ produces a
heat-stable toxin.
Staphylococcus aureus.
A patient presents with diarrhea that has lasted for weeks and is
accompanied by malaise, flatulence, weight loss, and abdominal cramps.
You detect the odor of sulfur on his breath. Based on the signs and
symptoms, you suspect __________, a protozoan. It is not easily found
in stool samples, so you do a string test.
Giardiasis
Clostridium difficile-associated diarrhea is usually preceded by
extended use of antiobiotics.
Disease-causing exotoxins are produced by all of the following
organisms EXCEPT Staphylococcus aureus Vibrio cholerae
Clostridium perfringens Clostridium botulinum
Shigella dysenteriae
Shigella dysenteriae
Which of the helminthic diseases is a common infestation found in the
southeastern United States?
Ascaris lumbricoides
All of the following infections can result form drinking contaminated
water EXCEPT cholera. giardiasis. cryptosporidiosis.
Cyclospora infection.
Trichenellosis
Trichenellosis
Aflatoxin is a(n) ________ associated with ingestion of contaminated ________.
mycotoxin; peanuts
Bacterial intoxications differ from bacterial infections of the
digestive system in that intoxications
have shorter incubation times
What is a Dane particle?
the infectious virion that causes HBV