Gastrointestinal Infections Flashcards
Obtain a good medical history, what information is pertinent?
Certain sexual practices Hospitalizations LTC facilities Child care facilities Foodborne or waterborne International travel Antimicrobial agents Immunocompromised host Animal exposure
Diarrhea defined:
↓in the consistency of bowel movements (i.e. unformed stool); ↑ in frequency of stools (> 3 per day)
NOTE:
Infectious diarrhea
Vomiting and diarrhea are responsible for much of the morbidity & mortality
Acute diarrhea
<14 days duration
Chronic diarrhea
≥ 14 days duration
Acute infectious diarrhea (I.D.):
Globally
-Younger children (< 5 yrs) are at higher risk of death from acute dehydrating diarrhea
In the United States:
-Highest risk of mortality is the elderly (as opposed to children, in the developing world)
Others at risk: travelers, campers, pts in chronic care facilities, military personnel stationed abroad, immunocompromised pts
Watery diarrhea vs. dysentery
Diarrhea is a condition that involves the frequent passing of loose or watery stools.
Dysentery is an intestinal inflammation, especially in the colon, that can lead to severe diarrhea with mucus or blood in the feces.
Watery diarrhea:
- appearance
- volume
- number per day
- reducing substances
- pH
- occult blood
- fecal PMNs
- watery
- increased: ++/+++
- < 10
- 0 to +++
- 5 - 7.5
- negative
- absent or few
Dysentary:
- appearance
- volume
- number per day
- reducing substances
- pH
- occult blood
- fecal PMNs
- bloody
- increased: +/++
- > 10
- 0
- 6 – 7.5
- positive
- many
Watery diarrhea:
Complications
1. dehydration
2. others
- could be severe
2. acidosis; shock; electrolyte imbalances
Dysentary:
Complications
1. dehydration
2. others
- mild
2. tenesmus; rectal prolapse; seizure
Watery diarrhea: Etiology
Vibrio cholerae
Enterotoxigenic E. coli (ETEC)
Rotaviruses
Noroviruses
Dysentary: Etiology
Shigella Salmonella Campylobacter spp. Enterohemorrhagic E. coli (EHEC) Yersinia spp. Clostridioides difficile
DYSENTERY
(bloody; inflammatory)
Cause:
Signs and Sx:
Cause is mostly bacterial (i.e. EHEC, Shigella, Salmonella, & Campylobacter)
Mucoid stool ± blood
Lower abdominal cramping w/ pain
Fever is more common
Colon is affected
Colonic ulceration occurs in addition to infection of upper epithelial cells
Cells are attacked and destroyed
Antimicrobials can eradicate the pathogen and stop the inflammation
Major systemic complications are possible
Almost always requires antibiotic treatment (IV antibiotics may be needed). EXCEPT for EHEC do NOT use antibiotics in EHEC!!
WATERY DIARRHEA
(enterotoxigenic; noninflammatory)
Cause:
Signs and Sx:
Cause is mostly viral (Norovirus & rotavirus > ETEC & Cholera)
Watery stool; no blood or mucous
± Cramping & pain
Fever is uncommon
Small bowel is affected
Infection & targeting of intestinal lumen & upper epithelial cells
No cell death; infection is due to toxins
Antimicrobials don’t eradicate the toxin
Less serious than dysentery; dehydration is major risk
Antimicrobial treatment not needed (oral or IV rehydration may be necessary)
Causative Organisms
Watery diarrhea (enterotoxigenic)
Non-invasive:
Rotavirus
Norovirus
Enterotoxigenic E. coli
Cholera (not in the U.S.)
Causative Organisms
Dysentery (bloody diarrhea)
Invasive
Shigella Salmonella Campylobacter Enterohemorrhagic E. coli Yersinia enterocolitica Clostridioides difficile
Watery diarrhea:
Norovirus
Account for > 90% of viral gastroenteritis among all age groups
Healthcare systems, cruise ships, college dorms
(previously known as Norwalk-like viruses)
Watery diarrhea:
Rotavirus
Is ubiquitous and infects most children < 5 yrs
After infection, 40% of children are protected against subsequent infection
Watery diarrhea: Vibrio cholerae (Cholera)
Gram-negative bacillus (similar to enterobacteriaceae)
Toxigenic C. cholerae serogroups 01 or 0139
Severe and voluminous diarrhea (watery diarrhea)
Not common in the U.S. due to sanitation of water systems
Watery diarrhea:
Enterotoxigenic E. coli (ETEC)
Accounts for ½ of all cases of E. coli diarrhea
Most common cause of traveler’s diarrhea
A common cause of food- and water-associated outbreaks
E. coli causing watery diarrhea
Toxin-producing:
Enteroaggregative E. coli (EAEC)
Enterotoxigenic E. coli (ETEC)
E. coli causing watery diarrhea
Non-toxin-producing
Enteroinvasive E. coli (EIEC)
Enteropathogenic E. coli (EPEC)
E. coli causing dysentery
Toxin-producing
Enterohemorrhagic E. coli (EHEC)
Viral Gastroenteritis
Norovirus:
All age groups Peak in winter 2-3 days Fecal-oral, food, water, environment Nausea, vomiting diarrhea, abdominal cramps, myalgia
Viral Gastroenteritis:
Rotavirus:
6 months to 2 years
October to April
3-7 days
Fecal-oral, water, food
Nausea, vomiting, diarrhea, fever, abdominal pain, lactose intolerance
Bacterial Gastroenteritis: E. coli
Enterotoxigenic
E. coli (ETEC)
Watery
- Toxin Production?
- Incubation period
- Duration
- Mode of transmission
- Common symptoms
- YES
- 1-3 days
- 3-4 days
- Contaminated food or water with human or animal feces
- Watery diarrhea and abdominal cramping
Responsible for ½ of all E. coli diarrheal illness; common cause of food/water outbreaks
Bacterial Gastroenteritis: E. coli
Entero-hemorrhagic
E. coli (EHEC):
Dysentary
- Toxin Production?
- Incubation period
- Duration
- Mode of transmission
- Common symptoms
- YES
- 3-4 days
- NR
- Uncooked beef or unpasteurized milk or juice
- Gastroenteritis, enterocolitis, sometimes bloody diarrhea and hemolytic-uremic syndrome
Bacterial Gastroenteritis:
Vibrio cholerae
- Incubation period
- Duration
- Mode of transmission
- Common symptoms
- 2 – 3 days
- 1 – 3 days
- Contaminated food or water with human feces usually in areas of inadequate treatment of sewage and drinking water
- Profuse watery diarrhea, vomiting, and leg cramps; Death can work within hours without treatment
Bacterial Gastroenteritis:
Salmonella nontyphoidal
- Incubation period
- Duration
- Mode of transmission
- Common symptoms
- 12 – 36 hours
- 1 – 5 days
- Contaminated food, water, or contact with infected animals
- Diarrhea (sometimes bloody), fever, and abdominal cramps
Bacterial Gastroenteritis:
Shigella spp.
- Incubation period
- Duration
- Mode of transmission
- Common symptoms
- 1 – 3 days
- 1 – 7 days
- Fecal-oral contaminated food or water with infected human feces
- Watery or bloody diarrhea (8-10 stools/day), severe abdominal pain, fever, and malaise
Enterohemorrhagic E. coli (EHEC):
Include strains that include:
Shigatoxigenic Escherichia coli (STEC)
Produces shiga toxin
Causes 50-60% of all EHEC infections
A type of EHEC, E. coli 0157:H7
can cause bloody diarrhea and hemolytic uremic syndrome (anemia and kidney failure)
A minority of the strains cause illness in humans
The strains that DO cause illness in humans are collectively known as Enterohemorrhagic E. coli (EHEC)
Major causes of foodborne illness
(Nontyphoid) Salmonella enterica
Gram-negative bacilli
Belongs to the Enterobacteriaceae family
Gastroenteritis is cause by:
- Serotypes Typhimurium and Enteritidis
- In the U.S. the largest burden of Salmonella infection is due to nontyphoidal serotypes
Shigella spp.
Produces shigellosis
Associated with poor sanitation or personal hygiene, inadequate water supply, malnutrition, and increased population density
S. sonnei and S. flexneri:
-The most common causes of gastroenteritis in the U.S.
S. dysenteriae type 1 and S. boydii
-Commonly acquired during travel
Watery Diarrhea (Acute Gastroenteritis) Enterotoxigenic E. coli (ETEC)
Produces watery diarrhea due to severe intestinal water secretion
Produces 2 toxins
-Heat-stable toxin (ST); heat-labile toxin (LT)
Watery Diarrhea (Acute Gastroenteritis) Rotavirus
Produces a viral enterotoxin
Induces changes in fluid balance by destroying the epithelial lining of the intestine, and vascular damage and ischemia in villi.
Watery Diarrhea (Acute Gastroenteritis)
Altered movement of ions and water, resulting in increased colonic secretion
Classic enteric pathogens that cause watery diarrhea in the U.S.
-V. cholerae, ETEC, rotavirus, and norovirus
Watery Diarrhea (Acute Gastroenteritis) V. cholerae
Produces classical secretory diarrhea due to cholera toxin
Toxin consists of 2 subunits, A and B
Toxin acts along the entire intestinal tract
Net effect of the cholera toxin: fluid secretion exceeds absorptive capacity
Inflammatory diarrhea (Dysentery)
Caused by 2 groups of organisms:
1.) Enterotoxin-producing, noninvasive bacteria
Adhere to the mucosa, activate cytokines, stimulate the intestinal mucosa to release inflammatory mediators