GI Infections 3: Intoxications and Infections of Intestines Flashcards
What are the rules of thumb when considering symptoms and incubation time of food intoxication?
What are the 3 etiologies that cause food intoxication?
How is this diagnosed?
How is this treated?
How can this be prevented?
Rules of Thumb of Food Intoxication:
Sx: n/v/d
usually short incubation period (2-12h)
NO FEVER
Not an infection: no fever, no fecal WBC
3 Etiologies:
Staphylococcus aureus - G+ coccus
Bacillus cereus - G+ rod, spores, aerobe
Clostridium perfringens Type A - G+ rod, spores, anaerobe
Diagnosis:
Clinically
Food sources tested if public
Culture food
Immunoassay food
Treatment:
usually none
Hydrate
IV and electrolytes if severely dehydrated
Prevention:
proper handling of food
What are the unique features and manifestations of the etiologies that can cause food intoxication?
Include symptoms
incubation
typical associated foods
Unique Features and Manifestations
S. aureus
sx: projectile vomiting, little/no diarrhea, no fever
1-4 hour incubation
highly processed foods - stored or handled improperly (mayonaisse containing salads, dairy, creme, salted foods)
B. cereus type 1
sx: n/v, little/no diarrhea
2-3 hour incubation - INTOXICATION
fried rice is classic example, carb rich
spores germinate to make toxin
toxin is heat stable
B.cereus type 2
sx: profuse diarrhea, little/no vomiting
10-12 hour incubation - INFECTION no fever
cooking kills vegetative cells but spores survive
spores germinate in intestine
common in meats, milk, veggies, and fish
C.perfringens
sx: abd cramps, diarrhea
8-24 hour incubation
cooking kills cells, spores remain
slow cooling allows germination of vegetative cells
bacterial cells make toxin as spores in intestine
meats, meat products, gravy
Rank the 3 causes of food intoxication in how common they are.
What are the common causes
S. aureus
highly processed foods
second most common cause
B. cereus
uncommon-spore production important
Fried rice - emetic form (type 1)
type 2 meaty (protein) diarrhea
C. perfringens
most common
spore production important
food held too long on the stove warming
Which etiologies leading to food intoxication can cause tissue damage and which do not?
No tissue damage - S.aureus, C. perfringens, and B.cereus
Severe C.perfringens type C can cause diffuse necrotizing enteritis
Describe the enterotoxins of each etiological cause of food intoxication.
S. aureus - 8 enterotoxins (heat stable)
cause n/v
enterotoxins → serotonin release → vagal afferent → emesis
B.cereus - 2 types of enterotoxins
1. heat stable, causes n/v, high carb foods
depsipeptide cereulide binds/activates 5-HT3 receptors → afferent vagus nerve → emesis
2. heat labile, cause diarrhea, high protein foods
hemolysin BL and nonhemolytic enterotoxin
increase cAMP levels → increased ion secretion → water follows
C. perfringens
heat labile enterotoxin, watery diarrhea, meat with vegetative cells
vegetative cells → spores in small intestine where they produce toxin
toxin disrupts ion transport → water follows
What etiologic agents can cause viral gastroenteritis?
What type of viruses are they?
What are the general manifestations of viral gastroenteritis?
Describe the pathophysiology.
How is this diagnosed?
How is this treated?
How could this be prevented?
Etiologies:
Rotavirus - naked dsRNA
Norovirus - naked ssRNA
Sapovirus - naked ssRNA
Astroviruses - naked ssRNA
Coronavirus (SARS CoV2) - enveloped ssRNA
Adenovirus - dsDNA
Manifestations:
low grade fever
abd pain, watery diarrhea, n/v
Pathology:
viruses invade and destroy mature epithelial cells in small intestine → decrease absorption of sodium and water → watery diarrhea
Diagnosis:
none usually
Rotavirus - EIA of stool looking for antigen
SARS CoV2 - nucleic acid amplification to find RNA in stool
Treatment:
self-limiting
fluids and electrolytes
If shock, severe dehydration, or altered give IV fluids
antiemetics/antidiarrheals for adults - not children
Prevention:
natural immunity incomplete in infants resulting in many episodes of viral gastroenteritis
less severe with age
norovirus infected should not prepare food while symptomatic or up to 3 days after they resolve
2 Rotavirus vaccines
2 SARS CoV-2 vaccines
Norovirus vaccin in phase 3 trials - 5 to 7 years
Describe the differences in symptoms, duration, and season of the viruses that cause viral gastroenteritis.
Rotavirus - naked dsRNA
2nd most common (post vaccine) cause of diarrhea in infants less than 2 (winter diarrhea)
n/v/d lasting 4-8 days
Norovirus - naked ssRNA
all ages, most common in children and infants
winter vomiting disease
most common cause of gastroenteritis overall
sudden onset
low fever, n/v and watery diarrhea
duration 12-60 hours
Sapovirus - naked ssRNA
like norovirus but less common
contaminated surfaces, food and water
Astroviruses - naked ssRNA
uncommon winter disease
diarrhea, vomiting uncommon
occurs in patients less than 5 years old
SARS CoV-2 - enveloped ssRNA
33% of patients have GI symptoms (n/v/d, anorexia), ageusia (loss of taste) and anosmia (loss of smell)
20% of COVID19 diarrhea is the first symptom
digestive alone or with respiratory symptoms (dry cough, dyspnea, sob)
Adenovirus - dsDNA
diarrhea
like rotavirus but occurs in older infants
can cause itussusception
What three organisms can cause noninflammatory bacterial gastroenteritis?
What are the symptoms of noninflammatory bacterial gastroenteritis and how are these different than viral gastroenteritis?
Noninflammatory Gastroenteritis
Etiologies:
Escherichia coli
Vibrio parahaemolyticus
Vibrio cholerae
Symptoms:
large volume diarrhea and abd cramps
vomiting less common than viral
no invasions of small intestine
no fecal leukocytes and no fever
What are the 3 types of E. coli?
3 Types of E. coli:
Enterotoxigenic E. coli (ETEC)
LT and ST toxins
Entero aggregative E. coli (EAEC)
adhere, mucus, heat stable toxin, plasmid encodid toxin
Enteropathogenic E. coli (EPEC)
attaching-effacing histopathology
no toxin
