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GI/Nutrition > Infectious Diarrhea > Flashcards

Infectious Diarrhea Flashcards

1
Q

How does the CDC define diarrhea in immuno-compromised individuals?

A

>1L/day

or

>20mL/kg/day

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2
Q

Acute diarrhea

  • Outcome:
  • BM/day:
  • Volume/day:
  • Most common time of year:
A
  • Outcome: Usually self-limited
  • BM/day: 3-7
  • Volume/day: <1L
  • Most common time of year: winter months (viral)
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3
Q

What is the length of the adult small intestine?

Where are most macronutrients absorbed?

A

SI: 3-8 meters in length

Most macronutrients are absorbed in the proximal 100-150 cm

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4
Q

What is the common etiology of small bowel infection?

A

Small bowel inflamed → Villous blunting → Malabsorption → Gut microbiome utilization of substrate → Abdominal cramping, bloating, gas and weight loss

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5
Q

What are the common etiologies of Large Bowel infection?

A

Lack of function → Lack of absorption → Frequent stools

or

Inflammation → Intracellular leakage → Frequent stools

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6
Q

What determines whether stool will be loose or regular in large bowel infectious disease?

A

Extent of colon involvement

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7
Q

What symptoms are associated with infectious large bowel?

A

Painful BM

Tenesmus

Urgency

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8
Q

Most gastroenteritis is ______ (bacterial/viral/fungal)

A

Viral

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9
Q

How is severe community acquired diarrhea defined?

A
  • ≥ 4 fluid stools/day
  • > 3 days
  • 87% bacterial
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10
Q

Salmonella Typhi

  • Classification:
  • Food association:
  • Animal association:
  • Risk factors for infection:
A
  • Classification: gram negative encapsulated bacilli
  • Food association: poultry, eggs, milk
  • Animal association: turtles
  • Risk factors for infection: summer and fall; young age, IBD, immune deficiencies
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11
Q

Which type of salmonella is more common in the US?

A

Non-typhoid (40% in patients < 15 y/o)

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12
Q

What can happen if the gallbladder is colonized during typhoid fever?

A

May be associated with gall stones and a chronic carrier state

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13
Q

What are the symptoms of an acute salmonella infection?

A
  • Anorexia
  • Abdominal pain
  • Bloating
  • Nausea
  • Vomiting
  • Bloody diarrhea
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14
Q

Patients with what disease are particularly susceptible to Salmonella osteomyelitis?

A

Sickle cell disease

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15
Q

Describe the pathogenesis of Salmonella infection?

A
  1. Quickly adapts to low pH (antibiotics can help it evade microbiome)
  2. Uptake into cell → Survival in modified phagosome
  3. Replication → induce migration of neutrophils → inflammatory response
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16
Q

Non-typhoid salmonella is generally self-limited except:

A

High fevers, Severe diarrhea (> 10 stools/day), hospitalized patient

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17
Q

Shigella

  • Classification:
  • Route of transmission:
  • Setting of transmission:
A
  • Classification: Gram negative bacilli that are unencapsulated facultative anaerobes
  • Route of transmission: fecal oral route HIGHLY CONTAGIOUS
  • Setting of transmission: Daycare and institutional settings
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18
Q
  • Describe the symptoms of Shigella infection:
  • How can the clinical course be shortened?:
  • What is contraindicated?:
A
  • Describe the symptoms of Shigella infection:
    • ~6 days of diarrhea, fever, and abdominal pain
  • How can the clinical course be shortened?:
    • antibiotic treatment
  • What is contraindicated?:
    • Antidiarrheal medications
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19
Q
  • What part of the GI tract is most commonly effected by Shigella?:
  • What are some rare features of Shigella?:
A
  • What part of the GI tract is most commonly effected by Shigella?:
    • Most commonly effects the left colon but the ileum may also be involved
  • What are some rare features of Shigella?:
    • Hemolytic Uremic Syndrome (HUS), Seizures, or Reactive arthritis
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20
Q

Campylobacter jejuni

  • Source:
  • Incubation period:
  • Leading cause of ______ bacterial diarrhea
A
  • Source: Undercooked poultry, unpasteurized milk or contaminated water
  • Incubation period: up to 8 days
  • Leading cause of acute bacterial diarrhea
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21
Q

Campylobacter jejuni

  • Dysentery prevelance:
  • Symptoms:
  • Stool appearance:
A
  • Dysentery prevelance: 15-50% of patients
  • Symptoms: influenza-like prodrome
  • Stool appearance: Watery or hemorrhagic, both small and large bowel symptoms
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22
Q

What are some complications of Campylobacter jejuni

A
  • Reactive arthritis
  • Erythema nodosum
  • Guillain-Barre syndrome (peripheral → central paralysis)
  • Abdominal pain
  • “Pseudoappendicitis”
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23
Q

Giardia lamblia

  • Classification:
  • Source:
  • Diarrhea classification (acute/chronic):
A
  • Classification: Flagellated protozoan
  • Source: fecally conaminated water or food
  • Diarrhea classification (acute/chronic): acute OR chronic diarrhea with upper abdominal bloating
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24
Q

Escheria coli

  • Classification:
  • Types:
A

Escheria coli

  • Classification: Gram-negative bacilli (colonizes the healthy GI tract)
  • Types:
    • Enterotoxigenic E. Coli (ETEC)
    • Enteroinvasiv E. Coli (EIEC)
    • Enteroaggregative E. Coli (EAEC)
    • Enterohemorrhagic E. Coli (EHEC)
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25
Q

Enterotoxigenic E. Coli (ETEC)

  • Principal cause of _______ ______
  • Route of transmission:
  • Toxins:
A
  • Principal cause of traveler’s diarrhea
  • Route of transmission: fecal-oral
  • Toxins:
    • Heat labile toxin (LT): similar to cholera toxin
    • Heat stabile toxin (ST): increases intracellular cGMP with effects similar to cAMP elevations caused by LT
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26
Q

What are the consequences of cAMP elevation in ETEC?

A
  1. secretion of Cl- thru its channel
  2. Prevention of reabsorption of NaCl at villus tips
  3. Net water secretion
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27
Q

Enteroinvasive E. Coli (EIEC)

  • Cells invaded:
  • Type of diarrhea:
  • Resembles ______ in pathogenesis
A

Enteroinvasive E. Coli (EIEC)

  • Cells invaded: gut epithelial cells
  • Type of diarrhea: bloody diarrhea
  • Resembles *Shigella *in pathogenesis
28
Q

Enteroaggregative E. Coli (EAEC)

  • Intearction with cells:
  • Function of Flagellan:
A
  • Intearction with cells: attaches to enterocytes by adherence fimbriae
  • Function of Flagellan:
    • Flagellan → Increased IL-8 → Intestinal inflammation
29
Q

Enterohemorrhagic E. Coli (EHEC)

  • AKA:
  • Source:
  • Associated syndrome:
A
  • AKA: 0157:H7
  • Source: Undercooked ground beef or mishandling of ground beef
  • Associated syndrome: HUS
    • Hemolysis, Thrombocytopenia, and Renal failure
30
Q

What is a problem with giving antibiotics for EHEC?

A

Antibiotics may induce HUS

31
Q

Vibrio Cholerae

  • Classification:
  • Source:
  • Toxin (and effects):
A
  • Classification: Gram-negative bacteria
  • Source: Contaminated drinking water; seafood
  • Toxin: Enterotoxin and cholera toxin which causes dz
    • Increased intracellular cAMP
    • Opens CFTR
    • Draws water into lumen with chloride into lumen
32
Q

Vibrio Cholerae

  • Outcome of most cases:
  • Outcome of Severe disease:
  • Incubation peroid:
A
  • Outcome of most cases: asymptomatic or mild diarrhea
  • Outcome of Severe disease: abrupt onset of water diarrhea and vomiting (may reach 1L/hour)
  • Incubation peroid: 1-5 days
33
Q

Norovirus

  • Source:
  • Areas of high risk:
  • Symptoms:
A

Norovirus

  • Source: contaminated food or water (person to person transmission as well)
  • Areas of high risk: Schools, hospitals, nursing homes, cruise ships
  • Symptoms: Nausea, vomiting, watery diarrhea, and abdominal pain
34
Q

Rotavirus

  • Age group at risk:
  • Symptoms:
  • Improvement with vaccine?:
A
  • Age group at risk: Children between 6 and 24 months of age
  • Symptoms: Vomiting and watery diarrhea for several days
  • Improvement with vaccine?: Data pending; previously the most common cause of childhood diarrhea
35
Q

Ascaris lumbricoides

  • Classification:
  • Transmission:
  • Disease association:
A
  • Classification: Nematode
  • Transmission: Fecal-oral
  • Disease association: can cause Ascaris pneumonitis
36
Q

Strongyloides

  • Transmission route:
  • Pathogenisis in the body:
  • Who is susceptible to overwhelming infections?:
A
  • Transmission route: can penetrate unbroken skin such as feet
  • Pathogenisis in the body:
    • Migrates through the lungs to to the trachea from where they are swallowed
    • Mature into adult worms in the intestines
    • Eggs can hatch in the intestine and release larvae that penetrate mucosa
  • Who is susceptible to overwhelming infections?:
    • Immunosuppressed individuals
37
Q

Necator Americanus and Ancylostoma duodenale

  • Classification:
  • Infection route:
  • Leading cause of _____ deficiency in the developing world
A
  • Classification: Hookworms
  • Infection route: Larval penetration through the skin → lungs → duodenum (swallowed) → suck blood and reproduce
  • Leading cause of **iron **deficiency in the developing world
38
Q

Immunocompromised hosts are susceptible to…(besides the typical players)

A
  • Parasites: cryptosporidium parvum, Isospora belli, Cyclospora, and Microsporia
  • Bacteria: MAC (mycobacterium avian complex)
  • Viral: CMV, HSV, adenovirus
39
Q

How is Nosocomial Diarrhea classified?

What determines is severity

A
  • New Diarrhea at least 72 hours after admission
  • Severity and length of stay depends mostly on age
40
Q

What are some nosocomial causes of diarrhea?

A
  • C. diff
  • Tube feeds
  • Medications
  • Fecal impaction
  • Ishemic Colitis
  • BMT patients
41
Q

Why is histology often unable to determine specific infections?

A

Most bacterial infections all induce a similar histopathology (Umbrella term: Acute self-limited colitis)

42
Q

What is the best way to identify bacterial pathogens in diarrhea associated infections?

A

Stool cultures

  • Pathogens are generally excreted continuously
43
Q

When are stool cultures indicated in diarrhea?

A
  • Severely ill
  • Outbreaks
  • Hospitalization
  • Immunocompromised patients (HIV)
  • Patients with comorbidities
  • At-risk employees (food handlers, daycare…)
44
Q

When do you order stool analysis for parasitic infection?

A
  • Persisiten diarrhea > 14 days
  • Travel to mountainous regions
  • Exposre to infants in daycare centers
  • Immune compromised
  • Community waterborne outbreak

Usually useless bc ova shed intermittently

45
Q

What treatment is indicated for infectious diarrhea? What circumstances must be true for this treatment to be effective?

A

HYDRATION!

  • Provided:
    • Intestinal glucose absorption via sodium-glucose cotransport remains intact
    • Intestine able to absorb water if glucose and salt are also present
46
Q

What other oral solutions are available for rehydration?

A
  • WHO-ORS (orally rehydrating solution)
  • Rehydralyte
  • Pedialyte available OTC
  • Gatorade not adequate for severely ill patients, but likely adequate for otherwise healthy patients
47
Q

When is IV rehydration indicated?

A
  • Indicated when the patient cannot tolerate oral rehydration
  • Electrolyte imbalance
    • Infant period (Kidney is not mature)
    • Patients on diuretics
48
Q

What empiric antibiotics are used to treat Traveler’s Diarrhea?

A

Prompt treatment with fluorquinolone or TMP-SMZ (can reduce duration from 3-5 to 1-2 days)

49
Q

What are the indications for empiric antibiotics?

A
  • Fever, bloody diarrhea, occult blood or fecal leukocytes in the stool (don’t use with EHEC or C. Diff)
  • Greater than 8 stools/day, volume depletion, symptoms > 1 week
50
Q

What are alternative agents to use in travelers diarrhea?

A

Azithromycin and erythromycin (if fluoroquinolone resistance is suspected)

51
Q

When would antimotility agents be indicated?

A

ONLY if fever is absent and stools are not bloody

Loperamide or diphenoxylate

52
Q

Clostridium Difficile

  • Classification:
  • Risk Factors:
  • Route of transmission:
A
  • Classification: gram positive spore forming anaerobic bacteria
  • Risk Factors:
    • Recent antibiotic use
    • Duration of hospital stay
    • Age (not disease causing in infants)
    • Immunosuppression
  • Route of transmission: Fecal-oral
53
Q

Why can C. Diff persists even with hand sanitizer use?

A

C. DIff spores cannot be removed with hand sanitizer (require soap and water)

54
Q

What are the Clostridium difficile toxins?

A
  • Toxin A (potent enterotoxin)
  • Toxin B (cytotoxin in vitro)
  • Binary Toxin (NAP1/027)
55
Q

What are the C. Diff virulence factors?

A
  • Flagellar proteins
  • Surface layer proteins
  • Surface exposed adhesion proteins
56
Q

How are C. DIff toxins tested?

A

C. Diff NAAT testing only for toxin B

**PCR testing **is becoming the new standard (lower false negative rate)

57
Q

What is the hypervirulent strain of C. Diff?

What gene is mutated?

A
  • BI/NAP2/027 strains
    • 16x more toxin A
    • 23x more toxin B
  • tcdC gene (toxin regulator gene) mutation
    • Increase FQ resistance
58
Q

What is one of the main risks with the BI/NAP1/027 strain of C. diff?

A

Toxic megacolon

59
Q

What is the possible cause of increasing C. diff incidence outside of the hospital?

A
  • Colonization and carriage reported in cows
  • C. diff has been isolated from a retail groun meat purchased in Canada
60
Q

C. Diff clinical presentation?

Severe forms?

A
  • Clinical presentation
    • Bloody watery diarrhea
    • Fever
    • Abdominal pain
    • Leukocytosis
    • Pseudomembranous colitis
  • Severe: toxic megacolon, sepsis, cytokine storm, death
61
Q

What are methods of C. Diff prevention?

A
  • Wearing gloves only
  • Hand washing
  • Isolation gowns
  • Use antibiotics judiciously
62
Q

How is C. Diff treated?

A

Vancomycin and metronidazole are mainstay therapies

  • Out-patient: Metronidazole
  • In-patient and toxic: Vancomycin
63
Q

What are risk factors for severe C. Diff infection?

A
  • Age > 65 y/o
  • Cr > 1.5 times baseline
  • WBC > 15K
64
Q

What percentage of patients will experience recurrence of C. Diff after initial infection?

A

10-35%

65
Q

What treatments are used for a recurrence of C. Diff?

A
  • Repeat metronidazole course
  • Vancomycin if not tried
  • Rifaximin
  • Probiotics
  • Fidaxomicin
  • Oral IVIG
66
Q

What is the MOA of Fidaxomicin?

What types of bacteria is it effective against?

A

Inhibits RNA polymerase

Effective against gram positive aerobes and anaerobes

67
Q

What new treatment can be used in recurrent C. Diff infection and has up to 95% efficacy?

A

Fecal transplant

GI/Nutrition (36 decks)

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