Gastroenteritis Flashcards
ACUTE GASTROENTERITIS:
Clinical syndrome of——-
With or without——
———leading cause——
• Clinical syndrome of diarrhea → more than three stool episodes in 24hours
• With or without vomiting that usually lasts for several days
• Infectious diarrhea is a leading cause of morbidity & mortality in children around the world
ACUTE GASTROENTERITIS causes
Viral
Bacterial
Parasite
Viral ACUTE GASTROENTERITIS
General information
watery stools with no blood or mucus
- Is the most common cause of diarrhea in children globally
- Associated with vomiting as well as diarrhea
- Incubation periods of hours to days
- Self-limited illnesses lasting 3–7 days
Viral causes of gastroenteritis
1)Rotavirus
• Cause damage to microvilli
• Is the most frequent cause of diarrhea in young children during the winter months.
• Primary infection with rotavirus may cause moderate to severe disease in infancy but is less severe later in life.
• Globally, the rotavirus vaccine has resulted in significant reductions in the incidence of acute gastroenteritis and hospitalizations due to rotavirus.
2)Caliciviruses (Norovirus):
• Cause Mucosal lesion
• Occurs in people of all ages
• Highly contagious
Is the most common cause of outbreaks of acute gastroenteritis
3)- Astroviruses
→Mucosal lesion
4)- Enteric adenoviruses (serotypes 40 and 41)
Mucosal lesion
Campylobacter jejuni:
• Is spread by person-to-person contact and by contaminated water and food, especially poultry, raw milk, and cheese
• The organism invades the mucosa of the jejunum, ileum, and colon.
Clostridium difficile:
• Causes bloody diarrhea & colitis
• Usually associated with prior antibiotic exposure.
• The organism produces spores that spread from person to person
• Diagnosis is made by detection of toxin in the stool.
• Infants younger than 12 months:
Should not be tested for C. difficile
They are frequently asymptomatically colonized with the organism in their stool, possibly due to a lack of the receptorrequired for infection.
Escherichia Coli types
1)EnteroPathogenic Escherichia Coli (EPEC):
• No toxin produced
• Adheres to apical surface & flattens the villi →prevent absorption →watery diarrhea
• Usually occur in children
2)EnteroToxigenic Escherichia Coli (ETEC):
• Cause traveler’s diarrhea (watery)
• Produce:
❖
❖
Heat-labile (cholera-like) enterotoxin →stimulates adenylate cyclase by ADP ribosylation of Gs
Heat-stable enterotoxin →stimulate guanylate cyclase
3) EnteroInvasive Escherichia Coli (EIEC):
• Invades the colonic mucosa
• Producing widespread mucosal damage with acute inflammation similar to Shigella, But without toxin
• Diarrhea is usually bloody with fever
4)EnteroHemorrhagic Escherichia Coli (EHEC):
• Most important pathogen →O157:H7
• Produce Shiga-like toxin
• Responsible for a hemorrhagic colitis (bloody diarrhea)
• Most cases of diarrhea associated with Hemolytic Uremic Syndrome (HUS):
❖Presents with microangiopathic hemolytic anemia, thrombocytopenia, and renal failure (No fever)
-5)EnteroAggregative Escherichia Coli (EAEC)
Adherence, mucosal damage
- Nontyphoidal Salmonella:
Produces diarrhea by invading the intestinal mucosa
• A large inoculum of organisms is required for disease because Salmonella is killed by gastric acidity
The incubation period for gastroenteritis ranges from 6–72hours but is usually less than 24hours
• Pathogenic mechanism: Invasion, enterotoxin
• Transmitted through:
Contact with infected animals (chickens, iguanas, other reptiles, turtles)
Contaminated food products, such as dairy products, eggs, and poultry
Shigella dysenteriae:
• Cause disease by producing Shiga toxin
• The incubation period is 1–7 days.
• Infected adults may shed organisms for up to 1 month
• Infection is spread by person-to-person contact or by ingestion of contaminated food with 10–100 organisms (acid stable)
• The colon is selectively affected.
• High fever and febrile seizures may occur in addition to diarrhea.
• Pathogenic mechanism: Invasion, enterotoxin, cytotoxin
Vibrio types
Vibrio cholerae
Enterotoxin
- Vibrio parahaemolyticus
Invasion, cytotoxin
Yersinia enterocolitica:
Is transmitted by pets and contaminated food, especially chitterlings.
• Infants and young children:
Have a diarrheal disease
• Older children:
Have acute lesions of the terminal ileum or acute mesenteric lymphadenitis
Mimicking appendicitis or Crohn disease.
• Postinfectious arthritis, rash, and spondylopathy may develop.
Bacterial causes of gastroenteritis
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Parasitic causes of gastroenteritis
Entamoeba histolytica:
• Infect the colon
• Amebiasis occurs in warmer climates
• Flask lesion in the colon
• Produce Cyst that resistant to physical destruction, enzyme & cytotoxin
2)Giardia lamblia:
• Cyst resistant to physical destruction
• Transmitted through ingestion of cysts from:
Contact with an infected individual
from food or water contaminated with infected feces.
• The organism adheres to the microvilli of the duodenal and jejunal epithelium.
• Insidious onset of progressive anorexia, nausea, gaseousness, abdominal distention, watery diarrhea, secondary lactose intolerance, and weight loss is characteristic of giardiasis
3)Spore-forming intestinal protozoa:
• Cryptosporidium parvum:
Causes mild, watery diarrhea in immunocompetent persons that resolves without treatment.
It can produce severe, prolonged diarrhea in persons with AIDS
• Isospora belli
• Cyclospora cayetanensis
• Microsporidia
Mechanism of diarrhea:
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Investigation of gastroenteritis
INVESTEGATIONS:
1)A stool culture:
➢ Don by:
✓ Diarrheal sample
✓ Rectal swab Inserting a swab into the rectum, then rotating it to obtain organisms from the rectal mucosal surface. It has a higher yield for identifying enteric pathogens, which are more likely to be found on the rectal mucosal surface than in the diarrhea itself.
2)A stool Rotazyme:
Is a rapid test which identifies the presence of rotavirus in the diarrhea.
3)Serum electrolytes & glucose:
Helpful in determining the degree of electrolyte imbalance, metabolic acidosis and hypoglycemia
