GI- Micro- Diarrhea Flashcards
Gatrotenteritis usually involves the stomach and the intestine and acute infectious diarrhea involves the and large intestine.
small intestine
small intestine
What are the 3 types of exotoxins?
Type I- Membrane-Acting Toxins
Type II- Membrane- Disrupting Toxins
Type III- Intracellular-Acting Toxins
Which exotoxin type binds to the host cell surface receptors and stimulate transmembrane signals (act in extracellular space)?
Ex- Superantigens (MHC and T cells) and some enterotoxins
Type I -Membrane -Acting toxins
Which exotoxin type acts on the host cell membranes and exert effects by damaging them?
-pore-forming toxins (C. Perfingens) and phospholipases and some enterotoxins
Type II- Membrane-Disrupting Toxins
Which extotoxin type has a binding region that binds a specific receptor (endocytosed) and activity regions that act on some intracellular target molecule?
-: A-B toxins and some enterotoxins
Type-III - Intracellular toxins
What type of toxins do enterotoxins express?
enterotoxins fall under all 3 enterotoxin types
What are protein toxins that cause diarrhea or vomiting where the host target is usually the intestines and sometimes Vagus N?
Enterotoxins
What exotoxin type is produced by Staphyloccocal enterotoxins A-E and and Heat-stable enterotoxin A (STa) and B(STb) of Escheriachia coli?
Type I- Membrane-acting toxins
What type of toxin is expressed by Clostridium perfringens?
Type II- membrane disrupting (pore forming)
What type of exotoxin type?
C. jejuni - Cytolethal distending toxin (Cj-CDT)
C. difficile Toxin A and B
Shiga toxins 1 & 2
Type III- Intracellular acting toxins (AB toxins)
What do the A and B subunits (Type III toxin) do?
A= activity (interacts with and usually interferes with intracellular processes).
A separates from B and gains access to cell cytoplasm
B=Binding (responsible for cellular specificity - mediates attachment and entry)
B mediates endocytosis into the cell
Which vibrio species is described:
Source of infection: fresh water
Route of infection: oral
clinical manifestation: cholera and gastroenteritis; rarely wound infections
Vibrio Cholerae O1 or O139
Which vibrio species is described:
Source of infection: seafood, sea water
Route of infection: oral and wound
clinical manifestation: gastroenteritis, wound and ear infxn
vibrio cholera (other strains- not O1 or O139)
Which vibrio species is described:
Source of infection: seafood
Route of infection: oral and wound exposure
clinical manifestation: Gastroenteritis & wound infections
Vibrio parahaemolyticus
Which vibrio species is described:
Source of infection: sea food, sea water
Route of infection: oral and wound exposure
clinical manifestation: gastroenteritis, wound infections, sepsis
Vibrio vulnificus
Describe vibrio species
gram negative
flagellated
Which vibrio is being described (cholerae, parahaemolyticus, or vulnificus):
Cholera- it begins with an abrupt onset of watery diarrhea and vomiting and can progress to severe dehydration, metabolic acidosis and hypokalemia, and hypovolemic shock
Gastroenteritis: milder form of diarrheal disease can occur in toxin-negative strains of V. cholerae O1 and non-O1 serotypes
Vibrio cholerae
Which vibrio is being described (cholerae, parahaemolyticus, or vulnificus):
gastroenteritis: it is generally self-limited, with an explosive onset of watery diarrhea and nausea, vomiting, abdominal cramps, headache, and low grade fever
wound infection: associated with exposure to contaminated water
vibrio parahaemolyticus
Which vibrio is being described (cholerae, parahaemolyticus, or vulnificus):
wound infection: severe, potentially fatal infections characterized by erythema, pain, bullae formation, tissue necrosis, septicemia
vibrio vulnificus
Which serogroups of v. cholerae can cause epidemic cholerae?
O1 and O139
Which V. cholerae virulence factors are described?
1.-hypersecretion of electrolytes and water
2-surface binding site receptor, mediates bacterial adherence to intestinal mucosal cells
3-adhesin factor
4-increases intestinal fluid secretion
5-increases intestinal permeability
1 cholera toxin
2 toxin coregulated pilus
3 chemotaxis
4 accessory cholera enterotoxin
5 zonula occludens toxin
Which Vibrio species:
- Kanagawa hemolysin (thermostable direct hemolysin [Vp-TDH]) - induces chloride secretion for watery diarrhea
- MOA includes increasing intracellular Ca2+
green colony on TCBS agar
V. parahaemolyticus
green colonies on the top
What is Kanagawa hemolysis and with which vibrio species is it associated?
B-hemolyticus on human blood agar, not sheep
[green colonies on Thiosulfate Citrate Bilesalts Sucrose (TCBS) agar because does not ferment sucrose]
V. parahaemolyticus
The V. cholerae toxins toxin coregulated pilus (TCP) and chemotaxis protein are what type of toxins?
attachment toxins to mucosa
Which 3 toxins contribute to waterry diarrhea in v. cholerae?
Cholera toxin (CTX)
Accessory cholera enterotoxin
zonula occludens toxin
note: rice water diarrhea (water, electrolytes, mucus)
V. cholerae produces no/some damage to the enterocytes, some/massive loss of fluid and electrolytes, no/some blood and WBCs in stool, and requires a high/low infectious dose?
no damage to enterocytes
massive loss
no blood and WBCs
high infectious dose
Describe the pathogenesis of V. cholerae?
Which V. cholerae toxin has 2 subunits that causes binding and endocytosis of the units in which the a is separated, stimulates GPCR, then AC pathway to increased cAMP and PKA to phosphorylated CFTR for electrolyte loss?
cholera toxin (CTP)
Which campylobacter species comes from poultry, cattle, sheep and can present with gastroenteritis, Guillain-Barre, and reactive arthritis?
Campylobacter jejuni
Which Campylobacter species is associated with pigs, poultry, sheep, and birds and is related to gastroenteritis and extraintestinal infections?
Campylobacter coli
Which diarrheal bacterial species is transmitted through consumption of undercooked or contaminated food or via contact with animals (a true zoonotic organism)?
campylobacter species
What is a major pathogen for inflammatory diarrhea and uses cytolethal distending toxin (CDT), a genotoxin, that causes histological damage to mucosal surfaces (absorptive microvilli) of the jejunum, ileum, and colon from e induction of G2/M cell cycle arrest leading to apoptosis ?
Campylobacter jejuni
What entero pathogen is associated with antibiotic use within the last 30 days that can result in pseudomembranous colitis (severe bloody diarrhea)?
C. difficile
Treatment with antibiotics causes massive death of the commensal bacteria that normally colonize the colon. This allows pathogenic bacteria to proliferate and to occupy an ecological niche that is normally occupied by harmless commensal bacteria. is an example of producing toxins that can cause severe bloody diarrhea in patients treated with antibiotics.
Clostridium difficle
What enteropathogenic species is being described:
- Two AB toxins
- Toxin A (TcdA) and B (TcdB) [both A or activity subunits] can activate glycosyltransferases that inactivate targets by adding a sugar moeity and can lead to apoptosis
- TcdA can activate inflammatory cells (cytokines, chemokines, ROS)
- TcdB activity leads to disruption of tight junctions and apoptosis.
Clostriodioides difficile
What is the virus that is a double capsid dsRNA (segmented) virus (which is unique) that can cause viral gastroenteritis?
- is associated more with diarrhea than vomit
- common in children 6 months - 2 yrs (<5 yrs worldwide)
- is also associated with respiratory symptoms
Reoviridae- Rotavirus
- rotovirus is/is not associated with food
- rotovirus has/ does not have a vaccine
- rotovirus is/is not common of persistent/chronic in HIV+
- is not associated with food
- does have a vaccine
- is not common in HIV+
What viral gastroenteritis is associated with children with T cell deficiencies, nursing homes, and college dorms?
Rotovirus
What is the clinical presentation of adults infected with rotovirus?
mild, asymptomatic
With rotovirus, a double capsid dsRNA virus, where does transcripton take place?
the capsid is uncoated and mRNA transcription occurs in the viral particle in the cytoplasm of host cell and then translation occurs in viroplasm (combo of viral and cellular components and lipids).
Which virus that produces viral gastroenteritis is one of the few viruses that produces toxin?
rotovirus
Why does infection with rotovirus lead to diarrhea and dehydration?
virus infects tips of villi in small intestine
infected cells are lysed by new virus
immature epithelial cells have reduced absorptive capacity (sugar, salts, water)
fluid accumulates in lumen
diarrhea and dehydration
Rotavirus non-structural protein 4 (NSP4) is released from infected and stimulates enterochromaffin cells (ECs, one type of enteroendocrine cell) to release 5- hydroxytryptamine (5-HT)15, a neurotransmitter that regulates gastrointestinal motility and induces nausea and .
enterocytes
vomiting
acute diarrhea lasts?
persistent diarrhea lasts?
chronic diarrhea lasts?
acute= 0-13 days
persistent= 14-29
Chronic = 30 +days
What 3 organisms or biological agents are mainly associated with vomiting?
preformed toxins
enteric viruses
nematodes
Which 7 pathologic agents are associated with watery diarrhea?
enteric viruses
c. perfingens
c. diff
vibrio species
enterobacteriaceae
protozoa
tapeworms
Which 4 infectious agents are involved with inflammatory diarrhea (fever, mucoid, bloody)?
enterobacteriaceae
campylobacter spp
entamoeba histolytica
noncholera vibrios
Enteric viruses can be involved with both vomiting and diarrhea
watery diarrhea
Enterobacteriaceae can be associated with both watery diarrhea and diarrhea
inflammatory diarrhea (fever, mucoid, bloody)
Which diarrheal type is associated with usually being self-limited, enteric viruses?
acute diarrhea (0-13 days)
What diarrheal length type is associated with protozoal infection?
persistent diarrhea (14-29 days)
Which diarrheal length type can be associated with immunocompromised?
chronic diarrhea (30+ days)
Which 2 enteric pathogens are associated with high fever and which is associated with afebfrile?
high fever= bacterial etiology, E. histolytica
afebrile= STEC (Shiga toxin producing E coli)
What pathogen is associated with watery diarrhea, vomiting, abdominal cramps, and fever?
Incubation 6 h - 2 days
Duration 48h- 7 days
Salmonella
What pathogen is associated with watery diarrhea, vomiting, abdominal cramps, and fever?
Incubation: 1-2 days
Duration: weeks
Enteropathogenic E. Coli (EPEC)
Which pathogens are associated with fever?
Salmonella
campylobacter
shigella
yersinia enterocolitica
enteropathogenic E. Coli (EPEC)
Enteroinvasive E. Coli (EIEC)
Which 2 E. Coli types are associated with watery diarrhea and and which 2 with bloody diarrhea?
watery- enteropathogenic (EPEC), enterotoxigenic (ETEC)
bloody- Enterohaemorrhagic (EHEC), Enteroinvasive (EIEC)
EPEC, ETEC, EHEC, and EIEC are all associated with diarrhea and .
vomiting
Which enteric pathogen is most associated with children 6-18 mnths?
Birth to 3 months and age over 50 and a history of atherosclerosis?
1-7 yrs old?
young adults?
rotavirus -6 to 18 mnths
nontyphoidal Salmonella- Birth to 3 months and age over 50 and a history of atherosclerosis
shigella- 1-7 yrs old
campylobacter- young adults
Immunocompromised people are most at risk for which 5 enteric pathogens?
Salmonella, Cryptosporidium, Campylobacter, Shigella, Yersinia
What 2 enteric pathogens are associated with hemochromatosis or hemoglobinopathy?
Y. enterocollitica and Salmonella
What level of infectious dose?
Shigella
STEC
Norovirus
Rotovirus
Giardia
Cryptosporidium
low infectious dose (<500)
What level of infectious dose?
Salmonella
Campylobacter jejuni
Moderate infectious dose
What level of infectious dose?
Enteroinvasive E. Coli
Enterotoxigenic E. Coli
Enteropathic E. Coli
Vibrio Cholerae
high infectious dose
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