CH 24 - Digestive System Infections Flashcards
1
Q
Cirrhosis
(definition)
A
Scarring of liver that interferes with normal liver function
2
Q
Dental caries
(definition)
A
Biofilm-mediated process that damages tooth enamel
3
Q
Dysbiosis
(definition)
A
Imbalance in normal microbiota
May be caused by taking antimicrobial medications
4
Q
Dysentery
(definiton)
A
Serious form of diarrhea characterized by blood, pus, & mucus in feces
5
Q
Gastroenteritis
(definition)
A
Acute inflammation of stomach & intestines
Syndrome of nausea, vomiting, diarrhea, abdominal pain
6
Q
Gingivitis
(definition)
A
Inflammation of gums
7
Q
Hemolytic Uremic Syndrome (HUS)
(definition)
A
Serious condition characterized by RBC breakdown & kidney failure
8
Q
Hepatitis
(definition)
A
Inflammation of the liver
9
Q
Microvilli
(defintion)
A
Tiny extensions from surfaces of cells such as those lining the intestinal villi
Increase surface area of mucosa
10
Q
Oral Rehydration Therapy (ORT)
(definition)
A
Treatment used to replace fluid & electrolytes lost due to diarrhea
11
Q
Potential Dangers in Thanksgiving Dinner
A
- Taenia solium (tapeworm)
- Clostridium botulinum
- Salmonella enterica (Campylobacter)
- Staphylococcus aureus
- Escherica coi
- Dental caries (Streptococcus mutans)
12
Q
Normal Microbiota of the Digestive System:
Esophagus/stomach/duodenum, oral cavity (tongue/teeth), lower small intestine/colon
A
Esophagus/stomach/duodenum:
- Few resident microbes
Oral cavity (tongue/teeth):
- Viridans streptococci
Lower small intestine & colon:
- Tremendous amount of microbes
- Act as microbial antagonists against transient microbes
13
Q
Antibiotic-Associated Diarrhea
A
Microbiota prevent colonization of some pathogenic bacteria
Use of antibiotics disrupts normal microbiota (mild to severe diarrhea)
Toxin-producing bacteria can colonize newly uninhabited intestine
- Damage epithelial cells
- Ex: Clostridium difficile
14
Q
Dental Caries:
Causative Agent
A
Streptococcus mutans
- G+ facultative anaerobe
- 10,000 CFU/mL in mouth
Other bacteria participate as well
15
Q
Streptococcus mutans Virulence Factors:
A
- Extracellular matrix of glucans from sucrose
- Tolerant to acidic environment
- Produce lactic acid when metabolizing sugars
16
Q
Dental Caries:
Symptoms
A
- Toothache
- Discoloration
- Roughening of enamel
- Tooth breakage
17
Q
Dental Caries:
Pathogenesis
A
- Attachment of bacteria to enamel & formation of cariogenic plaque
- Addition of sugars (sucrose) to environment causes drop in pH (~5)
- Due to fermentation
- Dissolves calcium phosphate of enamel
18
Q
Dental Caries:
Prevention
A
- Good oral hygiene
- Reduce/eliminate sugary foods - Fluoride
- Protects teeth from demineralization caused by acid
- Promotes remineralization
19
Q
Dental Caries:
Treatment
A
Drilling of diseased region & filling defect to restore contour of tooth
- Filling of composite or amalgam
20
Q
Peptic Ulcers:
Causative Agent
A
Helicobacter pylori
- G-
- Multiflagellated
- Microaerophile
21
Q
Peptic Ulcers:
Symptoms
A
- Stomach ache
- Abdominal pain
- Acid reflux
- Regurgitation
- Vomiting
- Belching
- Flatulence
- Nausea
22
Q
Untreated Helicobacter pylori Infection Can Cause:
A
- Peptic ulcers (duodenal or gastric)
- Gastroesophageal reflux (GERD)
- Cancers of esophagus & stomach
23
Q
Peptic Ulcers:
Pathogenesis
A
- Bacteria invade mucus & attach to gastric epithelial cells
- Helicobacter, its toxins, & inflammation cause layer of mucus to become thin
- Gastric acid destroys epithelial cells & underlying disease
24
Q
Peptic Ulcers:
Epidemiology (Urease Test)
A
Conversion of urea into CO2 can be detected in breath
Breakdown of urea by urease enzyme
- Releases ammonia & CO2
25
Peptic Ulcers:
Treatment
1. Proton pump inhibitors (PPIs)
- Reduce acid (heal stomach)
2. Antibiotics (kill bacteria)
- Clarithromycin
- Amoxicillin
26
Peptic Ulcers:
Barry Marshall
Drank H. pylori & developed ulcer
Marshall & Warren won Nobel Prize in 2005
27
Cholera:
Causative Agent
Vibrio cholerae
- G-
- Polar flagellum
Found naturally in aquatic environments (salt & fresh water)
Infects humans upon consumption of contaminated food & water
28
Cholera:
Symptoms
- Watery diarrhea in large volumes (1-6 L/hr; "rice-water" stool)
- Vomiting
- Muscle cramps
- Organ failure
- Cholera toxin (causes primary symptom)
29
Cholera:
Epidemiology
1.3-4 million cases/year
- 21-143,000 deaths/year (WHO)
1849 cholera epidemic
- 600 deaths/5000 population (12%)
30
Cholera:
Dr. John Snow
"Father" of modern epidemiology
Worked to determine source of cholera epidemic in London 1854
- Traced to single water source (water pump)
31
Cholera:
Pathogenesis
1. Bacteria ingested
2. Colonize small intestine
3. Express cholera toxin (CT)
- Encoded by lysogenic bacteriophage
32
Cholera:
Cholera Toxin (CT)
B subunit = binding
- Binds to gangliosides on epithelial cell surfaces
A subunit = active
1. Translocated
2. Catalyses ADP-ribosylation of Gs protein
3. Gs activates adenylate cyclase
4. Overproduction of cAMP
5. AMP causes ion channels to open
6. Massive secretion of ions & water into lumen
33
Cholera:
Treatment
Oral rehydration therapy (ORT)
- Electrolytes to successfully rehydrate pts
IV rehydration (non-responsive pts)
34
Cholera:
Prevention
Whole cell killed vaccine
- Somewhat protective but short-lived
- Doesn't work well in small children
Continued search for live vaccine
35
Shigellosis:
Causative Agent
Shigella
- G-
- Non-flagellated
Fecal-oral contact (primarily young children)
All species cause dysentery
36
Shigellosis:
Shigella species
1. S. flexneri
2. S. boydii
3. S. sonnei
4. S. dysenteriae
37
Shigellosis:
Pathogenesis
Invades cells in large intestine
1. Attaches to epithelial cell of colon
- Triggers endocytosis
- Multiplies in cytosol
2. Invades neighboring epithelial cells
- Avoids immune defenses
- Abscess forms as epithelial cells killed
3. Shigella that enters blood = quickly phagocytized & destroyed
38
Shigellosis:
Shiga Toxin (ST)
A-B toxin
- Carried on lysogenic bacterophage
Inhibits protein synthesis
Can cause hemolytic uremia syndrome (HUS)
- Associated with Enterohemorrhagic Escherichia coli (EHEC) which also carry ST NOT Shigella
39
Shigellosis:
Epidemiology
Human source of transmission (fecal-oral)
- Transmission occurs most often as result of overcrowding (common in day care)
NOT easily killed by stomach acid
Low infectious dose (as few as 10 organisms)
40
Shigellosis:
Prevention
Controlled by sanitary measures
NO vaccine
41
Shigellosis:
Treatment
Fluid & electrolyte replacement
Antibiotics
- Ampicillin & cotrimoxazole (shorten duration)
- 20% of Shigella species resistant
42
Escherichia coli Gastroenteritis:
Most diarrhea-causing E. coli fall into 4 groups
1. Enterotoxigenic E. coli (ETEC)
2. Enteroinvasive E. coli (EIEC)
3. Enteropathogenic E. coli (EPEC)
4. Enterohemorrhagic E. coli (EHEC)
43
Escherichia coli Gastroenteritis:
Enterotoxigenic E. coli (ETEC)
Most common cause of "traveler's diarrhea"
44
Escherichia coli Gastroenteritis:
Enteroinvasive E. coli (EIEC)
Disease closely resembles Shigella species
45
Escherichia coli Gastroenteritis:
Enteropathogenic E. coli (EPEC)
Causes outbreaks in hospital nurseries in developing countries
46
Escherichia coli Gastroenteritis:
Enterohemorrhagic E. coli
Often produces severe illness
- Production of Shiga toxin
Shiga toxin encoded on lysogenic bacteriophage
Many infected individuals develop hemolytic uremia syndrome (HUS)
Most common strain = O157:H7
47
Escherichia coli Gastroenteritis:
Symptoms
Infection depends on virulence of strain
Symptoms range from:
- Vomiting & loose stools
- Profuse diarrhea
- Severe cramps & bloody diarrhea
Recovery usually within 10 days
48
Escherichia coli Gastroenteritis:
Virulence factors
Depends on type of E. coli
1. Capsule
2. LPS
3. Pili
4. Toxins
49
Salmonellosis:
Causative Agent
Salmonella species
- G-
- Motile
Live in GI tract of animals
- Infect humans through contamination of water & food
50
Salmonellosis:
Types of Salmonella Associated with Human Diseases
1. S. enterica
2. S. typhi
Infect humans through contamination of water & food
51
Salmonellosis:
Symptoms
Gastroenteritis
- Nausea, vom, non-bloody stools
Vary depending on virulence of strain
Typically short-lived& milkd
52
Salmonellosis:
Pathogenesis
1. Ingested in contaminated food/water (chicken eggs)
2. Adhere to epithelial cells of small intestine
- Taken up by phagocytsosis (T3SS triggers)
3. Multiplies within phagosome
- Eventually kills host cells
4. Inflammatory response increases fluid secretion
- Diarrhea, fever, abdominal cramps
5. Salmonella shed in feces
53
Salmonellosis:
Serotype Typhi
Causes typhoid fever
Fecal-oral route
Can enter blood
- Phagocytized but NOT digested
- Phagocytes carry Salmonella to liver, spleen, bone marrow, & gallbladder
Can establish semipermanent in gallbladder
- Carriers can remain infected for years (even with treatment)
54
Salmonellosis:
Epidemiology
Bacteria survive long periods in environment
Chickens naturally carry (undercooked food source)
Household pets (turtles, iguanas, etc._
55
Salmonellosis:
Prevention
Cooking kills bacteria
Live attenuated vaccine
- Prevents typhoid fever
- 50-70% effective
56
Salmonellosis:
Treatment
Antibiotic therapy
Rehydration
57
Campylobacter jejuni
Pathogen
- G-
- Microaerophilic
Leading bacterial cause of diarrhea in US!!
58
Campylobacter jejuni:
Symptoms
Watery/foul-smelling diarrhea
Followed by:
- Bloody stools
- Fever
- Severe abdominal pain
59
Campylobacter jejuni:
Virulence Factors
1. Adhesins
2. Cytotoxins
3. Endotoxin
60
Campylobacter jejuni:
Major Source/Transmission
Major source = chickens
- 24% of raw chicken contains Campylobacter
- Commensal part of microbiome of chicken (no disease)
Transmitted fecal-oral route
61
Campylobacter jejuni:
Diagnosis
Based on S/S
62
Campylobacter jejuni:
Prevention
Proper hygiene after handling raw poultry
63
Campylobacter jejuni:
Treatment
Most cases resolve without treatment
64
Campylobacter jejuni:
Guillan-Barre Syndrome
Sequelae
~40% of cases due to Campylobacter
65
Viral Gastroenteritis:
Causative Agents
1. Cailciviruses
2. Astroviruses
3. Rotaviruses
- Most common cause in small children
- dsDNA
66
Viral Gastroenteritis:
Symptoms
- Abdominal pain
- Cramping
- Diarrhea
- Nausea
- Vomiting
67
Viral Gastroenteritis:
Pathogenesis
Rotaviruses infect epithelial cells of small intestine
Damaged lining fails to absorb fluids
- Watery diarrhea
68
Viral Gastroenteritis:
Epidemiology
More cases occur in winter
Transmitted fecal-oral route
69
Viral Gastroenteritis:
Treatment
Fluid & electrolyte replacement
70
Viral Gastroenteritis:
Prevention
Vaccine for rotavirus
71
Norovirus
ssRNA virus
- Small
- Non-enveloped
- Calicivirus family
Originally caused Norwalk Virus
72
Norovirus:
Symptoms
- Nausea
- Vomiting
- Watery diarrhea
Symptoms subside in 12-60 hrs
73
Norovirus:
Pathogenesis
Infects epithelium of upper small intestine
- Epithelial cell death
- Decreases production of digestive enzymes
Epithelium recovers in ~2 weeks
74
Norovirus:
Epidemiology
23 million cases in US annually
Transmission = fecal-oral route
Outbreaks often occur in institutions, cruise ships, etc.
- Contaminated food/water
75
Norovirus:
Prevention
Hand washing & disinfectants
NO vaccine
76
Norovirus:
Treatment
NO proven antiviral med
77
Viral Hepatitis:
Symptoms
- Jaundice
- Abdominal pain
- Fatigue
- Nausea
- Vomiting
- Appetite loss
Symptoms may occur years after infection
78
Viral Hepatitis:
Pathogenesis
Hepatitis A virus (HAV)
- Fecal-oral route
Other Hepatitis viruses (HBV, HCV)
- Sexual contact or blood-borne
Host immune system responses = responsible for liver damage`
79
Viral Hepatitis:
Diagnosis
- Jaundice
- Enlarged liver
- Fluid in abdomen
Most individuals with HAV will be sick for several weeks but recover completely
80
Viral Hepatitis:
Prevention
Good hygiene
Vaccine against HAV
81
Giardia Infections:
Causative Agent
Giardia lamblia
- Diarrhea-causing protozoan
1 of most frequent causes of human waterborne disease in US
82
Giardia Infections:
Transmission (& pathogenesis)
1. Ingestion of cyst
- Fecal contaminated food/water, streams
- Chlorination doesn't kill (boiling & filtration works)
2. Trophozoite adheres to small intestine via sucking disk
- Interferes with fat absorption
83
Giardia Infections:
Symptoms
- Non-bloody, foul-smelling diarrhea
- Abdominal cramps
84
Entamoeba histolytic
(general overview)
Diarrhea
- Ranging from mild asymptomatic to severe dysentery
May invade intestinal mucosa
- Causes erosions
May penetrate portal blood circulation
- Forms abscesses in liver & lung
100,000 deaths worldwide
