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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
What do Heat labile toxin (LT) and Heat stable toxin (ST) do?
LT: is simliar to cholera toxin ST: increases intracellular cGMP with effects similar to the cAMP elevations caused by LT
26
How does elevated cAMP lead to diarrhea?
cAMP --> secretion of Cl- thru its channel --> prevents reabsorptoin of NaCl at villus tips --> net water secretion
27
Resembles Shigella in its pathogenesis Invades gut epithelial cells produces a bloody diarrhea
Enteroinvasive E. coli organisms (EIEC)
28
Attaches to enterocytes by adherence fimbriae | Flagellan --> increased IL-8 --> intestinal inflammation
Eneteroaggregative E. coli orangisms (EAEC)
29
Acquired by undercooked or mishandling of ground beef | Associated with Hemolyic Uremic Syndrome (HUS)
Enterohemorrhagic E. coli (EHEC)
30
What is HUS?
Hemolysis Thrombocytopenia Renal failure *Antibiotics may induce HUS
31
Vibrio cholerae is a....
Grame negative bacteria
32
How do you acquire Vibrio cholerae?
Contaminated drinking water | Seafood-associated disease
33
What does the cholera toxin do?
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
How do patients with Vibrio cholerae generally present?
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
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
Norovirus
36
Most common cause of childhood diarrhea and diarrhea-related deaths worldwide Children between 6-24 months of age most vulnerable Vaccine now available
Rotavirus
37
Ascaris lumbricoides
Parasitic disease - nematodes Infects more than 1 billion worldwide Fecal-oral Can cause ascaris pneumonitis
38
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
Strongyloides
39
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
Necator americanus | Ancylostoma duodenale
40
What are some causes of diarrhea to worry about specifically in immunocompromised patients?
Parasites: cryptosporidium parvum, isospora belli, cyclospora, microsporia Bacteria: MAC Viral: CMV, HSV, adenovirus HIV-induced diarrhea -- separate entity
41
What is nosocomial diarrhea?
New diarrhea at least 72hours after admission Increases the length of stay from 1 week to 1 month Elderly - increased incidence and mortality
42
What are some causes of nosocomial diarrhea?
``` C. diff Feeding tubes (osmotic) Medications Fecal impaction (overflow incontinence) Ischemic colitis BMT patients - GVHD ```
43
When do you order stool cultures?
``` Severely Ill Outbreaks Require hospitalization Immunocompromised patients (HIV) Patients with comorbidities (IBD) Employees that require neg stool culture to return to work ```
44
How do stool for ova and parasites need to be conducted?
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
When do you order an O & P?
``` Persistent diarrhea > 14 days Travel to mountainous regions Exposure to infants in daycare centers Immune compromised Community waterborne outbreak ```
46
When do you use ELISAs or DFA microscopy>
To check for Giardiasis & Cryptosporidium antigen in stool Sensitivities > 90% Specificity close to 100%
47
What is ALWAYS the first line treatment?
Hydration, hydration, hydration
48
When should IV rehydration be used?
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
What abx should be used for traveler's diarrhea?
Prompt treatment with fluoroquinolone or TMP-SMX -- can reduce duration from 3-5 days to 1-2 days
50
What are some indications to use empiric antibiotics?
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
Should anti motility agents be used for diarrhea?
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
C. diff is....
a gram positive spore forming anaerobic bacteria ** Found to be associated with use of abx especially Clindamycin
53
What are some of the risk factors for the development of C. diff?
``` Recent abx use Age (does not cause disease in infants) Duration of hospital stay Chemo IBS AIDs ```
54
Why should you wash your hands when dealing with C. diff as opposed to using hand sanitizer?
It is a spore -- so not killed with alcohol
55
What toxins does C. diff produce?
Toxin A Toxin B Binary (present in much more virulent strains)
56
How do you test for Toxin A and B?
PCR -- new standard and lower false negative rate
57
What is the hypervirulent strain of C. diff?
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
C. diff infections are increasing in which populations?
Young, healthy Women in peri-partum No exposure to abx
59
How does C. diff typically present?
``` Bloody, watery diarrhea Fever Abdominal pain Leukocytosis Pseudomembranous colitis ``` In severe forms: toxic megacolon, sepsis/cytokine storm, colonic perforation and death
60
How do you treat C. diff?
Vancomycin and metronidazole mainstay therapies Out-patient: Metro In-patient: Vanco
61
What constitutes C. diff severe disease?
Age > 65 Cr > 1.5x baseline WBC > 15K
62
What percentage of patients experience recurrence of C. diff infection? What are some risk factors for recurrence?
10-35% of patients Risk factors: Continued antibiotics, age and co-morbidities, antacid medication
63
What is the treatment for recurrence of C. diff?
``` Repeat Metronidazole Vancomycin (if not tried) -- longer course with taper Rifaximin Probiotics Fidaxomicin Oral IVIG ```
64
How does Fidaxomicin (Dificid) work?
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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