Lecture 13: Infectious Diarrhea Flashcards
What is acute infectious diarrhea?
Less than 4 weeks
What is chronic infectious diarrhea?
Greater than 4 weeks
History is key. What do we need to find?
- Characteristics of diarrhea (bloody/watery, osmotic?)
- child vs. elderly
- Travel history
- recently hospitalized
- Diet
- Medications
- Medical history (immunocompromised)
What things in the physical exam do we need to know?
Temperature > 103 Tenesmus Bloody diarrhea Prolonged course of over 2 weeks If you have these 4 things, you need to have diagnostic testing with hospitalization If not, you can treat symptoms
What is tenesmus?
Feeling like you have to go all the time but only a little comes out at a time
This is something that is characteristic of inflamed bowel
What are host factors for susceptibility for infection?
Gastric acidity (less acidic = less protection) Gastric mucus GI motility (slower motility = more chance of infection) Less intestinal microbial flora Systemic and local immune system deficit
What are bacteria-virulence factors to watch out for?
Adherence
Enterotoxin
Cytotoxin
Mucosal invasion
What is the classic enterotoxin? MoA of cholera?
Cholera enterotoxin
Vibrio cholera produces cholera toxin A and B
Cholera toxin A and B do two things
1. On the villus, cholera toxin A increases cAMP activity (because toxin B binds to GM1 ganglionosides) which inactivates HCO3/Cl and H/Na antiports (so less ions coming into the cell/therefore less fluid coming in)
2. On the crypt side, A and B toxin defuses through and activates cAMP to increase secretion of Cl-, thereby secreting more fluid/ions
Therefore, cholera makes you both absorb less and secrete more
Cholera toxin B is NON-toxic whle cholera toxin A is what is responsible for cAMP upregulation
What is the MoA of C diff?
Cytotoxins A and B
Are endocytosed
Glycosylates Rho and weakens the tight junctions
This increases inflammation and activates macrophages/neutrophils to come over
Cytotoxins = cell death!
-direct cytotoxicity
What is the difference between enterotoxin and cytotoxin?
Enterotoxin = toxin that changes function of cell but not cell death Cytotoxin = toxin that kills cell (direct cytotoxicity)
What does fever suggest about acute diarrhea?
- commonly associated with invasive pathogens
2. could be rotavirus in kids
What does vomiting suggest?
- viral diarrhea
- common in cholera
- common with staph aureaus
What does bloody stools suggest?
- invasive and cytotoxin-producing pathogens
- suspect EHEC infection in absence of fecal leukocytes
- NOT with viral agents and enterotoxins producing bacteria
What are the most common causes non-bloody infectious diarrhea?
Most common type of diarrhea
- viruses (most common)
- bacteria
- parasites
What is the most common non-bloody virus infectious diarrhea?
- Calcivirus (norovirus, Norwalk-like virus)
- Rotavirus
- Adenovirus
- Astrovirus
- Torovirus
What are the clinical symptoms of norovirus?
Very short (24-72 hours) SHORTEST Diarrhea, vomiting, abdominal cramps Fecal-oral
What are the characteristics of rotavirus?
1. fecal oral CHILDHOOD diarrhea Tropics = all year round Temperate = winter only Vomiting followed by watery diarrhea Duration = 5-7 days
What are the characteristics of adenovirus?
Adenovirus causes diarrhea
Serotypes 40 and 41
Children less than 2 years and immunocompromised
Duration = 5-12 days LONGEST
What bacteria are food-borne that lead to non-bloody diarrhea?
- Enterotoxigenic E. coli (ETEC)
- Diffusely adhering E. coli
- Vibrio cholera
- Non-cholera vibrio
What bacteria are non-food-borne that lead to non-bloody diarrhea?
- Aeromonas
- Bacteroides fragilis
- Diffusely adhering E. coli
What are causes on non-bloody parasitic diarrhea?
- Giardia
- Cryptosporidium
- Cyclospora
- Trichella spiralis
- Dientamoeba fragilis
- Blastocystis hominis
- Strongyloides
What are causes of BLOODY infectious diarrhea?
- food borne bacteria
i. Shigella
ii. Salmonella
iii. Campylobacter
iv. Enterohemorrhagic E. coli (EHEC)
v. Enteroinvasive E. coli
vi. E. coli - Non-food borne bacteria
C. Difficile (rarely) - Parasites
-E. histolytica
-schistosomiasis
What is proctitis?
An inflammation of the anus and the lining of the rectum
What happens when you have proctitis and tenesmus, that are pseudo diarrhea (because low volume just increased frequency)?
- gonorrhea
- treponema pallidum
- chlamydia
- herpes simplex 2
- shigella
What are food-borne toxin mediated diarrhea?
- Clostridium perfingens
- Staph aureus
- bacillus cereus
- clostridium botulinum
- bacillus anthracis
In immunosuppressed patients?
- nonbloody
i. microsporidia
ii. cryptosporidium
iii. cyclospora
iv. isospora - bloody
i. CMV
ii. HSV
If you have diarrhea that starts in the hospital, what do you look for?
C. diff
What are the causes of traveler’s diarrhea?
- parasites
i. giardia
ii. E. histolytica
iii. Cryptosporidium - Bacteria
i. Ecoli (ETEC and EAEC)
ii. Campylobacter
iii. Shigella
iv. Salmonella
v. Aeromonas
vi. Plesiomonas
vi. Vibrio spp
How do you evaluate an immunocompromised patient with diarrhea?
Look for CMV
Also look for an “spor” types of parasites
What are the three groups of patients?
- normal
- immunocompromised
- hospital acquired (just look for C diff)
What causes bloody stool via pork (or meat)?
Yersinia
What are not causes of bloody stool?
- giardia
- cryptosporidium
- plesiomonas
All of them are watery
How do you diagnose acute diarrhea?
Look for Fecal Leukocytes (fecal lactoferrin and calprotectin) -allows you to look for inflammation CBC Stool culture Stool ova and parasites (ELISA for giardia) Stool C diff
What are the big 3 for diarrhea stool analysis?
- Salmonella
- Shigella
- Campylobacter
Also can be - Aeromonas
- Plesiomonas
What are the causes of chronic diarrhea (inflammatory)?
- bacteria
i. C diff
ii. Aeromonas
iii. Yersinia
iv. Salmonella
v. Campylobacter
vi. Tuberculosis
vii. Gonorrhea
viii. Treponema pallidum
ix. chlamydia - Viral
i. CMV
ii. HSV (proctitis) - Parasites
i. E. hystolytica
ii. Strongyloides
iii. Schistosomiasis
What are the causes of malabsorptive/osmotic diarrhea?
- Tropheryma whipplei (Whipple’s)
- systemic infection, followed by weight loss, neurologic symptoms, cardiac inflammation, hyperpigmentation, arthralgia
- Giardia
What is the diagnostic criteria for Whipple’s?
Done by endoscopy
Lipid laden macrophages in histology
Darker area = Tropheryma whipplei
What are the causes of SECRETORY chronic diarrhea?
- Cryptosporidium
- Cyclospora
- Microsporidia
- Isospora
What is the diagnostic evaluation of chronic diarrhea?
- C. diff
- crypto + giardia (looking for osmotic)
- Culture = aeromonas
- Fecal fat (qualitative)
If you see eosinophils in your CBC, what is the cause of diarrhea?
Parasitic (something with “spor” in it)
What is an example of a case where you do NOT treat infectious diarrhea?
Enterohemorrhagic E. coli
Treatment with antibiotics may lead to hemolytic uremic syndrome (HUS)
What do you do if you suspect EHEC?
Do not treat with antibiotics!
Hemolytic uremic syndrome
What is the significance of hemolytic uremic syndrome?
HUS
Something that can occur as a result of antibiotic treatment of EHEC
