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GI > Infectious Diarrhea > Flashcards

Infectious Diarrhea Flashcards

1
Q

What does the acute diarrhea clinical course look like?

A

Usually self limited
Average of 3-7 BM per day
Volume <1 L/day
Occurs mostly in winter months (viral)

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2
Q

What is the etiology of small bowel infectious diarrhea?

A

The small bowel becomes inflamed –> villous blunting –> malabsorption –> Gut microbiome utilization of substrate –> And cramping, bloating, gas and weight loss

Cellular or Intracellular leaking

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3
Q

What is the etiology of large bowel infectious diarrhea?

A

Lack of function –> lack of absorption –> frequent stools

Inflammation –> intracellular leakage –> frequent stools

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4
Q

What is the most common cause of gastroenteritis?

A

Viral

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5
Q

Bacterial agents that commonly cause acute gastrointestinal disease

A 
Salmonella
Shigella
Campylobacter
E. Coli O157:H7
Clostridium Difficile
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6
Q

Viral agents that commonly cause acute gastrointestinal disease

A

Calicivirus
Rotavirus
Adenovirus
Astrovirus

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7
Q

Protozoa that commonly cause acute gastrointestinal disease

A

Giardia
Cryptosporidium
Entamoeba histolytic

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8
Q

What is responsible for 40% of diarrhea in patients <15 yo?

A

Salmonella typhi (non-typhoid type)

Risk factors: summer and fall, young age, IBD, immune deficiencies

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9
Q

What is Typhoid fever?

A

Gallbladder colonization that can be associated with gallstones and a chronic carrier state

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10
Q

What are some characteristics of Salmonella that allow it to infect?

A

It quickly adapts to a low pH (stomach)
Uptake into cell, survives in modified phagosome and replicates
Induces migration of neutrophils –> inflammatory response

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11
Q

Salmonella are…

A

Gram negative encapsulated bacilli

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12
Q

Shigella are…

A

Gram negative bacilli, encapsulated, facultative anaerobes

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13
Q

How is shigella spread?

A

Fecal oral route – highly contagious (as few as 10 organisms, acid resistant)

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14
Q

Where does Shigella most commonly infect?

A

The left colon (ileum may also be involved) – can mimic Crohn’s disease

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15
Q

Should you give someone with Shigella antibiotics or antidiarrheal?

A

Antibiotic treatment shortens the clinical course

Antidiarrheal medications are contraindicated (delays bacterial clearance)

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16
Q

What are some things that the production of Shiga toxin can produce?

A

Hemolytic Uremic Syndrome, Seizures, or Reactive arthritis

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17
Q

What is the leading cause of acute bacterial diarrhea world wide?

A

Campylobacter jejuni

33% of food borne illnesses

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18
Q

How does Campylobacter jejuni present?

A

Usually an influenza-like prodrome (fever, malaise, myalgia)
Dysenter (15-50%)
Self limited - no abx
Watery or hemorrhagic – both small and large bowel symptoms

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19
Q

What are some other things that Campylobacter jejuni can do to patients?

A

Reactive arthritis or erythema nodosum
Guillain-Barre syndrome
Pseudoappendicitis

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20
Q

Giardia lamblia is a…

A

Flagellated protozoan

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21
Q

How do you get Giardia lamblia?

A

Fecally contaminated water or food

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22
Q

How does Giardia lamblia affect a patient?

A

Acute or chronic diarrhea with upper abdominal bloating

Small bowel disease

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23
Q

E. coli is a….

A

gram negative bacilli

Colonizes healthy GI tract

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24
Q

Principal cause of traveler’s diarrhea

Fecal-oral route

A

Enterotoxigenic E. coli (ETEC) organisms

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25
Q

What do Heat labile toxin (LT) and Heat stable toxin (ST) do?

A

LT: is simliar to cholera toxin
ST: increases intracellular cGMP with effects similar to the cAMP elevations caused by LT

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26
Q

How does elevated cAMP lead to diarrhea?

A

cAMP –> secretion of Cl- thru its channel –> prevents reabsorptoin of NaCl at villus tips –> net water secretion

27
Q

Resembles Shigella in its pathogenesis
Invades gut epithelial cells
produces a bloody diarrhea

A

Enteroinvasive E. coli organisms (EIEC)

28
Q

Attaches to enterocytes by adherence fimbriae

Flagellan –> increased IL-8 –> intestinal inflammation

A

Eneteroaggregative E. coli orangisms (EAEC)

29
Q

Acquired by undercooked or mishandling of ground beef

Associated with Hemolyic Uremic Syndrome (HUS)

A

Enterohemorrhagic E. coli (EHEC)

30
Q

What is HUS?

A

Hemolysis
Thrombocytopenia
Renal failure

*Antibiotics may induce HUS

31
Q

Vibrio cholerae is a….

A

Grame negative bacteria

32
Q

How do you acquire Vibrio cholerae?

A

Contaminated drinking water

Seafood-associated disease

33
Q

What does the cholera toxin do?

A

It causes an increase in intracellular cAMP which opens the cystic fibrosis transmembrane conductance regulator (CFTR) –> releases chloride ions into the lumen –> draws after into the lumen

34
Q

How do patients with Vibrio cholerae generally present?

A

Most are asymptomatic or suffer mild diarrhea
Severe disease – abrupt onset of water diarrhea and vomiting
Incubation period of 1-5 days

May reach up to 1 L per hour –> dehydration, hypotension, electrolyte imbalances, anuria, shock and death.

35
Q

Half of all gastroenteritis outbreaks worldwide
Acquired by contaminated food or water, but person-to-person transmission as well
Nausea, vomiting, watery diarrhea, and abdominal pain
Self limited

A

Norovirus

36
Q

Most common cause of childhood diarrhea and diarrhea-related deaths worldwide
Children between 6-24 months of age most vulnerable
Vaccine now available

A

Rotavirus

37
Q

Ascaris lumbricoides

A

Parasitic disease - nematodes
Infects more than 1 billion worldwide
Fecal-oral
Can cause ascaris pneumonitis

38
Q

Larvae live in fecally contaminated ground soil
Can penetrate unbroken skin (feet)
Migrate through the lungs to the trachea – swallowed
Mature into adult worms in the intestines
Eggs can hate within the intestine and release larvae that penetrate the mucosa –> vicious cycle referred to as auto infection
Persist for life and immunosuppressed can develop overwhelming infections

A

Strongyloides

39
Q

Hookworms
Infect 1 billion worldwide
Infection by larval penetration through the skin
Develop in lungs then migrate up the trachea and are swallowed
In duodenum, larvae mature and adult worms attach to the mucosa, suck blood and reproduce
Leading cause of Iron deficiency anemia in developing world

A

Necator americanus

Ancylostoma duodenale

40
Q

What are some causes of diarrhea to worry about specifically in immunocompromised patients?

A

Parasites: cryptosporidium parvum, isospora belli, cyclospora, microsporia
Bacteria: MAC
Viral: CMV, HSV, adenovirus
HIV-induced diarrhea – separate entity

41
Q

What is nosocomial diarrhea?

A

New diarrhea at least 72hours after admission
Increases the length of stay from 1 week to 1 month
Elderly - increased incidence and mortality

42
Q

What are some causes of nosocomial diarrhea?

A 
C. diff
Feeding tubes (osmotic) 
Medications
Fecal impaction (overflow incontinence) 
Ischemic colitis
BMT patients - GVHD
43
Q

When do you order stool cultures?

A 
Severely Ill 
Outbreaks
Require hospitalization 
Immunocompromised patients (HIV)
Patients with comorbidities (IBD) 
Employees that require neg stool culture to return to work
44
Q

How do stool for ova and parasites need to be conducted?

A

Many false negatives b/c ova shed intermittently
Repeat 3 x – 3 consecutive days, 24 hours apart
Useless in most patients
Not cost effective

45
Q

When do you order an O & P?

A 
Persistent diarrhea > 14 days
Travel to mountainous regions
Exposure to infants in daycare centers
Immune compromised
Community waterborne outbreak
46
Q

When do you use ELISAs or DFA microscopy>

A

To check for Giardiasis & Cryptosporidium antigen in stool
Sensitivities > 90%
Specificity close to 100%

47
Q

What is ALWAYS the first line treatment?

A

Hydration, hydration, hydration

48
Q

When should IV rehydration be used?

A

When they cannot tolerate oral – vomiting, excessive diarrhea
If there is an electrolyte imbalance – infant period (kidney fxn not mature), patients on diuretics, cardiac meds or similar meds

49
Q

What abx should be used for traveler’s diarrhea?

A

Prompt treatment with fluoroquinolone or TMP-SMX – can reduce duration from 3-5 days to 1-2 days

50
Q

What are some indications to use empiric antibiotics?

A

Fever, bloddy diarrhea and presence of occult blood or fecal leukocytes
Greater than 8 stools per day, vol depletion symptoms > 1 week, hospitalized and immunocompromised

*Use Fluoroquinolone for 3-5 days – or Azithromycin/Erythromycin if resistance suspected

51
Q

Should anti motility agents be used for diarrhea?

A

Most of the time they are not needed – but Loperamide or diphenoxylate may be used
Only if fever is absent and stools are not blood

** remember these drugs may facilitate the development of HUS in EHEC

52
Q

C. diff is….

A

a gram positive spore forming anaerobic bacteria

** Found to be associated with use of abx especially Clindamycin

53
Q

What are some of the risk factors for the development of C. diff?

A 
Recent abx use
Age (does not cause disease in infants)
Duration of hospital stay 
Chemo
IBS
AIDs
54
Q

Why should you wash your hands when dealing with C. diff as opposed to using hand sanitizer?

A

It is a spore – so not killed with alcohol

55
Q

What toxins does C. diff produce?

A

Toxin A
Toxin B
Binary (present in much more virulent strains)

56
Q

How do you test for Toxin A and B?

A

PCR – new standard and lower false negative rate

57
Q

What is the hypervirulent strain of C. diff?

A

BI/NAP1/O27 strain
16x more toxin A
23x more toxin B
tcdC gene (toxin regulator gene) mutation

Increase fluoroquinolone resistance
Mortality rates up to 6.9% and higher rate of toxic megacolon

58
Q

C. diff infections are increasing in which populations?

A

Young, healthy
Women in peri-partum
No exposure to abx

59
Q

How does C. diff typically present?

A 
Bloody, watery diarrhea
Fever
Abdominal pain
Leukocytosis
Pseudomembranous colitis

In severe forms: toxic megacolon, sepsis/cytokine storm, colonic perforation and death

60
Q

How do you treat C. diff?

A

Vancomycin and metronidazole mainstay therapies
Out-patient: Metro
In-patient: Vanco

61
Q

What constitutes C. diff severe disease?

A

Age > 65
Cr > 1.5x baseline
WBC > 15K

62
Q

What percentage of patients experience recurrence of C. diff infection? What are some risk factors for recurrence?

A

10-35% of patients

Risk factors: Continued antibiotics, age and co-morbidities, antacid medication

63
Q

What is the treatment for recurrence of C. diff?

A 
Repeat Metronidazole
Vancomycin (if not tried) -- longer course with taper 
Rifaximin
Probiotics
Fidaxomicin 
Oral IVIG
64
Q

How does Fidaxomicin (Dificid) work?

A

Inhibits RNA polymerase
Useful for gram positive aerobes and anaerobes
Low serum conc, high fecal conc

** really expensive

GI (34 decks)

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