Infectious Diarrhea Flashcards
How does the CDC define diarrhea in immuno-compromised individuals?
>1L/day
or
>20mL/kg/day
Acute diarrhea
- Outcome:
- BM/day:
- Volume/day:
- Most common time of year:
- Outcome: Usually self-limited
- BM/day: 3-7
- Volume/day: <1L
- Most common time of year: winter months (viral)
What is the length of the adult small intestine?
Where are most macronutrients absorbed?
SI: 3-8 meters in length
Most macronutrients are absorbed in the proximal 100-150 cm
What is the common etiology of small bowel infection?
Small bowel inflamed → Villous blunting → Malabsorption → Gut microbiome utilization of substrate → Abdominal cramping, bloating, gas and weight loss
What are the common etiologies of Large Bowel infection?
Lack of function → Lack of absorption → Frequent stools
or
Inflammation → Intracellular leakage → Frequent stools
What determines whether stool will be loose or regular in large bowel infectious disease?
Extent of colon involvement
What symptoms are associated with infectious large bowel?
Painful BM
Tenesmus
Urgency
Most gastroenteritis is ______ (bacterial/viral/fungal)
Viral
How is severe community acquired diarrhea defined?
- ≥ 4 fluid stools/day
- > 3 days
- 87% bacterial
Salmonella Typhi
- Classification:
- Food association:
- Animal association:
- Risk factors for infection:
- 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
Which type of salmonella is more common in the US?
Non-typhoid (40% in patients < 15 y/o)
What can happen if the gallbladder is colonized during typhoid fever?
May be associated with gall stones and a chronic carrier state
What are the symptoms of an acute salmonella infection?
- Anorexia
- Abdominal pain
- Bloating
- Nausea
- Vomiting
- Bloody diarrhea
Patients with what disease are particularly susceptible to Salmonella osteomyelitis?
Sickle cell disease
Describe the pathogenesis of Salmonella infection?
- Quickly adapts to low pH (antibiotics can help it evade microbiome)
- Uptake into cell → Survival in modified phagosome
- Replication → induce migration of neutrophils → inflammatory response
Non-typhoid salmonella is generally self-limited except:
High fevers, Severe diarrhea (> 10 stools/day), hospitalized patient
Shigella
- Classification:
- Route of transmission:
- Setting of transmission:
- Classification: Gram negative bacilli that are unencapsulated facultative anaerobes
- Route of transmission: fecal oral route HIGHLY CONTAGIOUS
- Setting of transmission: Daycare and institutional settings
- Describe the symptoms of Shigella infection:
- How can the clinical course be shortened?:
- What is contraindicated?:
- 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
- What part of the GI tract is most commonly effected by Shigella?:
- What are some rare features of Shigella?:
- 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
Campylobacter jejuni
- Source:
- Incubation period:
- Leading cause of ______ bacterial diarrhea
- Source: Undercooked poultry, unpasteurized milk or contaminated water
- Incubation period: up to 8 days
- Leading cause of acute bacterial diarrhea
Campylobacter jejuni
- Dysentery prevelance:
- Symptoms:
- Stool appearance:
- Dysentery prevelance: 15-50% of patients
- Symptoms: influenza-like prodrome
- Stool appearance: Watery or hemorrhagic, both small and large bowel symptoms
What are some complications of Campylobacter jejuni
- Reactive arthritis
- Erythema nodosum
- Guillain-Barre syndrome (peripheral → central paralysis)
- Abdominal pain
- “Pseudoappendicitis”
Giardia lamblia
- Classification:
- Source:
- Diarrhea classification (acute/chronic):
- Classification: Flagellated protozoan
- Source: fecally conaminated water or food
- Diarrhea classification (acute/chronic): acute OR chronic diarrhea with upper abdominal bloating
Escheria coli
- Classification:
- Types:
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)
Enterotoxigenic E. Coli (ETEC)
- Principal cause of _______ ______
- Route of transmission:
- Toxins:
- 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
What are the consequences of cAMP elevation in ETEC?
- secretion of Cl- thru its channel
- Prevention of reabsorption of NaCl at villus tips
- Net water secretion
Enteroinvasive E. Coli (EIEC)
- Cells invaded:
- Type of diarrhea:
- Resembles ______ in pathogenesis
Enteroinvasive E. Coli (EIEC)
- Cells invaded: gut epithelial cells
- Type of diarrhea: bloody diarrhea
- Resembles *Shigella *in pathogenesis
Enteroaggregative E. Coli (EAEC)
- Intearction with cells:
- Function of Flagellan:
- Intearction with cells: attaches to enterocytes by adherence fimbriae
- Function of Flagellan:
- Flagellan → Increased IL-8 → Intestinal inflammation
Enterohemorrhagic E. Coli (EHEC)
- AKA:
- Source:
- Associated syndrome:
- AKA: 0157:H7
- Source: Undercooked ground beef or mishandling of ground beef
- Associated syndrome: HUS
- Hemolysis, Thrombocytopenia, and Renal failure
What is a problem with giving antibiotics for EHEC?
Antibiotics may induce HUS
Vibrio Cholerae
- Classification:
- Source:
- Toxin (and effects):
- 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
Vibrio Cholerae
- Outcome of most cases:
- Outcome of Severe disease:
- Incubation peroid:
- 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
Norovirus
- Source:
- Areas of high risk:
- Symptoms:
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
Rotavirus
- Age group at risk:
- Symptoms:
- Improvement with vaccine?:
- 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
Ascaris lumbricoides
- Classification:
- Transmission:
- Disease association:
- Classification: Nematode
- Transmission: Fecal-oral
- Disease association: can cause Ascaris pneumonitis
Strongyloides
- Transmission route:
- Pathogenisis in the body:
- Who is susceptible to overwhelming infections?:
- 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
Necator Americanus and Ancylostoma duodenale
- Classification:
- Infection route:
- Leading cause of _____ deficiency in the developing world
- 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
Immunocompromised hosts are susceptible to…(besides the typical players)
- Parasites: cryptosporidium parvum, Isospora belli, Cyclospora, and Microsporia
- Bacteria: MAC (mycobacterium avian complex)
- Viral: CMV, HSV, adenovirus
How is Nosocomial Diarrhea classified?
What determines is severity
- New Diarrhea at least 72 hours after admission
- Severity and length of stay depends mostly on age
What are some nosocomial causes of diarrhea?
- C. diff
- Tube feeds
- Medications
- Fecal impaction
- Ishemic Colitis
- BMT patients
Why is histology often unable to determine specific infections?
Most bacterial infections all induce a similar histopathology (Umbrella term: Acute self-limited colitis)
What is the best way to identify bacterial pathogens in diarrhea associated infections?
Stool cultures
- Pathogens are generally excreted continuously
When are stool cultures indicated in diarrhea?
- Severely ill
- Outbreaks
- Hospitalization
- Immunocompromised patients (HIV)
- Patients with comorbidities
- At-risk employees (food handlers, daycare…)
When do you order stool analysis for parasitic infection?
- 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
What treatment is indicated for infectious diarrhea? What circumstances must be true for this treatment to be effective?
HYDRATION!
- Provided:
- Intestinal glucose absorption via sodium-glucose cotransport remains intact
- Intestine able to absorb water if glucose and salt are also present
What other oral solutions are available for rehydration?
- WHO-ORS (orally rehydrating solution)
- Rehydralyte
- Pedialyte available OTC
- Gatorade not adequate for severely ill patients, but likely adequate for otherwise healthy patients
When is IV rehydration indicated?
- Indicated when the patient cannot tolerate oral rehydration
- Electrolyte imbalance
- Infant period (Kidney is not mature)
- Patients on diuretics
What empiric antibiotics are used to treat Traveler’s Diarrhea?
Prompt treatment with fluorquinolone or TMP-SMZ (can reduce duration from 3-5 to 1-2 days)
What are the indications for empiric antibiotics?
- 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
What are alternative agents to use in travelers diarrhea?
Azithromycin and erythromycin (if fluoroquinolone resistance is suspected)
When would antimotility agents be indicated?
ONLY if fever is absent and stools are not bloody
Loperamide or diphenoxylate
Clostridium Difficile
- Classification:
- Risk Factors:
- Route of transmission:
- 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
Why can C. Diff persists even with hand sanitizer use?
C. DIff spores cannot be removed with hand sanitizer (require soap and water)
What are the Clostridium difficile toxins?
- Toxin A (potent enterotoxin)
- Toxin B (cytotoxin in vitro)
- Binary Toxin (NAP1/027)
What are the C. Diff virulence factors?
- Flagellar proteins
- Surface layer proteins
- Surface exposed adhesion proteins
How are C. DIff toxins tested?
C. Diff NAAT testing only for toxin B
**PCR testing **is becoming the new standard (lower false negative rate)
What is the hypervirulent strain of C. Diff?
What gene is mutated?
- BI/NAP2/027 strains
- 16x more toxin A
- 23x more toxin B
- tcdC gene (toxin regulator gene) mutation
- Increase FQ resistance
What is one of the main risks with the BI/NAP1/027 strain of C. diff?
Toxic megacolon
What is the possible cause of increasing C. diff incidence outside of the hospital?
- Colonization and carriage reported in cows
- C. diff has been isolated from a retail groun meat purchased in Canada
C. Diff clinical presentation?
Severe forms?
- Clinical presentation
- Bloody watery diarrhea
- Fever
- Abdominal pain
- Leukocytosis
- Pseudomembranous colitis
- Severe: toxic megacolon, sepsis, cytokine storm, death
What are methods of C. Diff prevention?
- Wearing gloves only
- Hand washing
- Isolation gowns
- Use antibiotics judiciously
How is C. Diff treated?
Vancomycin and metronidazole are mainstay therapies
- Out-patient: Metronidazole
- In-patient and toxic: Vancomycin
What are risk factors for severe C. Diff infection?
- Age > 65 y/o
- Cr > 1.5 times baseline
- WBC > 15K
What percentage of patients will experience recurrence of C. Diff after initial infection?
10-35%
What treatments are used for a recurrence of C. Diff?
- Repeat metronidazole course
- Vancomycin if not tried
- Rifaximin
- Probiotics
- Fidaxomicin
- Oral IVIG
What is the MOA of Fidaxomicin?
What types of bacteria is it effective against?
Inhibits RNA polymerase
Effective against gram positive aerobes and anaerobes
What new treatment can be used in recurrent C. Diff infection and has up to 95% efficacy?
Fecal transplant
