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S2B1: Infectious Disease > Gastrointestinal infections V > Flashcards

Gastrointestinal infections V Flashcards

1
Q
A
  • 1-3 can occur both in infection & intoxicaion
  • long incubation time – infection
  • short incubation time – intoxication
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2
Q

What is food intoxication?

Symptoms?

Common etilogies?

A
  • Food intoxication: intoxication/toxemia following ingestion of food
  • Symptoms
    • short incubation times (2-12 hrs)
    • rapid onset
    • not an infection –
      • no fever
      • absence fecal leukocytes
  • Etiologies
    • Staphylococcus aureus – gram + cocci
    • Bacillus cereus– gram + bacilli aerobe
    • Clostridium perfringens Type A– gram + bacilli anaerobe
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3
Q

What are unique feautures of food intoxication caused by S. aureus?

A
  • Symptoms
    • projectile vomitinng
    • little or no diarrhea
    • no fever
  • 1-4 incubation
  • contaminated foods usually stored or handled improperly (highly processed)
    • mayonnaise containing salads
    • creme puffs
    • dairy products
    • salted foods
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4
Q

What are unique feautures of food intoxication caused by B. cereus?

A
  • Type 1 – grow in carbs
    • symptoms
      • nausea, vomiting, little if any diarrhea
    • incubation– 2-3 hours – INTOXICATION
    • Food examples
      • fried rice
      • cooking rice kills cells,
        • improperly stored
        • spores geminate & make toxin
          • toxin is heat stable
          • ingest reheated food
  • Type 2– grow in proteins
    • symptoms
      • profuse diarrhea, little if any vomiting (still no fever)
      • incubation time – 10-12 hours – INFECTION
    • Example-
      • meats, milk, vegetables, and fish
      • cooking food kills vegetative cells, but spores survive
        • ingest spores
          • germinate in intestine
          • cells grow & make toxin in intestine
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5
Q

What are unique feautures of food intoxication caused by C. perfringens?

A
  • Symptoms
    • abdominal cramps and diarrhea
    • diarrhea in less than 24 hrs
  • incubation – 8-24 hrs
  • Examples
    • meats, meat products, gravy
    • cooking food kills cells, spores remain
      • slow cooling of food spores germinate adn large number of cells grow
      • bacterial cells make toxin when the becoem spores in the intestine
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6
Q

Compare and contrast the epidemiology of food intoxication caused by S. aureus, B. cereus, and C. perfringens

A
  • S. aureus
    • highly processed foods
    • second most comon cause
  • B. cereus
    • uncommon– spore production important
    • fried rice leading food source for emetic form (type 1)
  • C. perfringens
    • most common cause of food poisoning
    • spore production important
    • food held too long on the stove warming
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7
Q

Describe the general pathology of food intoxication

A
  • Pathology
    • usually not tissue damage wtih S. aureus, C. perfringens, and B. cereus
    • severe cases of C. perfringens Type C can get a diffuse, necrotizing, enteritis
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8
Q

Describe the toxins produced by S. aureus, B. cereus, and C. perfringens

A
  • S. aureus 8 enterotoxins that are heat stable – nausea and vomiting
    • enterotoxins causes serotonin release; binds to vagal afferent neurons causign emesis
  • B. cereus has 2 types enterotoxins
    • Type I
      • heat stable & causes nausea and vomiting depsipeptide cereulide - binds/activates 5-HT3 receptors that increase afferent vagus nerve stimulation
      • associated with high carbohydrate containing food
    • Type II
      • heat labile enterotoxins caues diarrhea
      • hemolysin BL and nonhemolytic enterotoxin
      • associated with high protein foods
        • increases cAMP levels - increased ion secretion- water follows
  • C. perfringens
    • heat labile enterotoxin - watery diarrhea
      • cells go from vegetative cells to spores in small intestine and produce toxin
      • toxin disrupts ion transport
      • water follows the ions
      • meat products wtih many Clostridium vegetative cells growing in it
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9
Q

How is food intoxication diagnosed?

A
  • clinical grounds
    • people usually get over this in a relatively short period of time
  • food sources are tested if associated with public institutions
    • culture food
    • immunoassay foods
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10
Q

What is the treatment for food intoxication?

prevention?

A
  • Treatment
    • none usually
    • make sure patient is drinking plenty of fluids
    • in severly dehydrated give IV fluids and electrolytes
  • Prevention
    • proper handling of foods
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11
Q
A
  • Bacillus cereus Type I
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12
Q
A
  • Depsipeptide cerulide
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13
Q
A
  • Clostridium perfringens
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14
Q
A
  • Staphylococcus aureus
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15
Q

What are the most common etiological causes of viral gastroenteritis?

A
  • Rotavirus (naked ds RNA)
  • Norovirus (naked ssRNA)
  • Sapovirus (naked ssRNA)
  • Astrovirus (naked ssRNA)
  • Coronavirus (SARS CoV-2-enveloped ssRNA)
  • Adenovirus (dsDNA)
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16
Q

What are the general manisfestations of viral gastroenteritis?

A
  • low grade fever
  • abdominal pain
  • watery diarrhea
  • nausea
  • vomiting
17
Q

Uniqe aspects of rotavirus caused gastroenteritis?

A
  • second most common in babies <2
    • vomiting and diarrhea can last 4-8 days
    • winter
  • was first before vaccine
18
Q

Uniqe aspects of caliciverde caused gastroenteritis?

A
  • Noroviruses
    • sudden onset of low-grade fever, nausea, vomiting and water diarrhea
    • infants/children/adults/ - winter
    • symptoms last 12-60 hrs
    • most common cause overall
    • most common in children and infants
  • Sapovirus
    • like norovirus; less common
  • Astrovirus
    • diarrhea, vomiting is uncommon
    • in children less than 5
    • winter
19
Q

Uniqe aspects of SARS CoV-2 caused gastroenteritis?

A
  • Digestive symptoms can occur alone or wth respiratory symptoms
  • In 20% of patients with COVID-19 diarrhea is the first symptom
  • 33% of mild COVID-19 paients have digestive system symptoms
    • diarrhea, nausea, vomiting, anorexia, loss of taste (ageusia) and loss of smell (anosmia)
  • if patient has digestive symptoms a little over half have respiratory symptoms too
  • Ageusia and anosmia are uniqe to this virus and rarely occur in other gastroenteritis viruses
20
Q

Uniqe aspects of adenovirus caused gastroenteritis?

A
  • like rotavirus (winter diarrhea)
  • in older infants
  • can cause intussusception (one part of the intestine slides inside an ajdacent part)
21
Q
A
  • Fever
22
Q

Desscrive the pathology of viral gastroenteritis

A
  • viruses invade and destroy mature epithelial cells
  • infect cells in the small intestine
    • causes decrease in absorption or sodium and water from bowel lumen
    • watery diarrhea results
  • ** look at handout or virulence factor file for details
23
Q

How is viral gastroenteritis diagnosed and treated?

A
  • Diagnosed
    • none are usually performed
    • rotavirus infections- EIA of stool to look for rotavirus antigen
    • Nucleic acid amplification tests can be used to detect SARS CoV-2 RNA in feces
  • Treatment
    • self-limiting disease
    • fluids and electryolytes by mouth
    • if in shock, severe dehydration, or decreased consciousness
      • give IV fluids
    • Antiemetics and antidiarrheal drugs for adults but not recommended for children
24
Q

Prevention of viral gastroenteritis

A
  • Prevention
    • natural immunity is incomplete in infants
    • they will have many episodes of viral gastroenteritis
    • less severe as we age
    • persons infected with norovirus should not prepare food while symptomatic or up to 3 days after symptoms resolve
  • Two rotavirus vaccines are available
  • Tow SAS CoV-2 vacciens are available
  • Norovirus vaccine in phase 3 trials- maybe in 5-7 years
25
Q

What are the general characteristics of noninflammatory bacterial gastroenteritis?

Common etiological causes?

A
  • Features
    • large volume diarrhea and abdominal cramps
    • comiting less common than in viral
    • no invasion of small intestine
    • no fecal leukocytes
  • Etiological agents
    • Escheria coli
    • Vibrio parahaemolyticus
    • Vibrio cholerae
26
Q

What are the 3 types of E. coli that can produce noninflammatory bacterial gastroenteritis?

Pathology of each?

A
  • Enterotoxigenic E coli (ETEC)- infantile diarrhea & Traveler’s diarrhea
    • LT (heat labile) and ST (heat stable) toxins
    • LT-ADP ribosylates GTP-bindign protein
      • activates adenylate cyclase
        • increase protein kinase
          • stimulate Cl- secretion adn inhibits NaCl absorption
    • ST- stimulates guanylate cyclase
      • increase cGMP
        • stimulates Cl- secretion and inhibits NaCl absorption
  • Enteraggregative E. coli (EAEC)- Traveler’s diarrhea; more persistent
    • adhere (aggregative adherence fimbriae I)
      • stacked brick arrangement
    • mucus
      • produces biofilm
    • heat stable toxin– produces 2
      • plasmid encoded toxin
      • toxins induce fluid secretion– watery diarrhea
  • Enteropathogenic E/ coli (EPEC)- infants less than 6 months old
    • Attaching- bundle forming pili
    • Effacing- inject Tir binds to intimin
      • actin polymerization
        • loss of surface integrity –> cell death
    • no toxin
27
Q

What is the most common cause of traveler’s diarrhea?

A
  • ETEC
    • 30-50% of travelers to high-risk areas will get TD
    • ingesting contaminated water and food
28
Q

What is the diagnostic critera for noninflammtory bacterial gastroenteritis?

Treatment?

Prevention?

A
  • Diagnosis
    • no usually done
    • grow E. coli on macConkey agar
      • test for LT toxin on mammalian cells or with ELISA or usa a DNA probe to detect LT gene
  • Treatment
    • peroral or intravenous fluids and elctrolytes
    • bismuth subsalicylate for cramps
    • antibiotics
  • Prevention
    • instructions concerning food and beverage selection
    • use of bismuth subsalicylate
    • prophylactic antibotics for immunosuppressed and immunocompromised

S2B1: Infectious Disease (6 decks)

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