1. Infectious Diarrhea
Nicole Leone
July 29th, 2013

2. Viral vs. Bacterial Age Presence of blood or mucus Exposures
Bacterial and parasitic agents generally cause gastroenteritis in children at an older age (2-4 years)
Viral pathogens cause gastroenteritis in children < 2yo
Presence of blood or mucus
Presence of gross blood or mucus suggests bacterial or parasitic infection
Bloody diarrhea is rare with viral gastroenteritis
Occult blood does not count
Exposures
Bacterial or parasitic agents are usually associated with foreign travel, exposure to poultry or other farm animals, consumption of processed meat
Fecal WBCs
Presence of fecal leukocytes suggests bacterial/parasitic etiology
Indicates inflammation, does not distinguish infectious vs. non-infectious

3. Work Up Fecal Leukocytes Stool Culture Stool for Ova and Parasites
Examining fecal smear stained with Wright stain
Stool Culture
Bacterial pathogen will be identified in 15-20% of cases
Not recommended for non-bloody diarrhea of brief duration in otherwise healthy children
Stool for Ova and Parasites
Indicated for children who have traveled to endemic area
Viral Antigen tests of stool
Helpful in distinguishing acute viral gastroenteritis from a bacterial process
Urine Culture
Infants and children with UTIs can have diarrhea
Abdominal Ultrasound
Useful to r/o intussusception, appendicitis

4. Salmonellosis
S.typhimurium and S.enteritidis are most common serotypes
S.enteritidis assoc. w/ foodborne disease (eggs)
Most common in children < 5yo, with highest incidence in 1st year
Younger patients have higher rates of associated bacteremia
Nausea, vomiting, fever, diarrhea, cramping
Occur within 8-72 hours of contaminated food ingestion
Higher dose of ingested bacteria correlates with increased severity of diarrhea
Bloody diarrhea is less common than with Shigella

5. Salmonellosis Course Treatment
< 5% develop invasive disease (bacteremia)
Bacteremia can lead to endocarditis, osteomyelitis
Usually self-limited, fever resolves within 72h, diarrhea within 4-10 days
Treatment
Supportive
Antibiotics are indicated for children < 3mos, and those at high risk for invasive disease (malignancies, hemoglobinopathies, HIV, chronic GI disease)
Antibiotics: Ampicillin/Amoxicillin, Bactrim, Cefotaxime, Ceftriaxone
Antibiotics are NOT indicated for patients with uncomplicated (non-invasive) gastroenteritis caused by NON-TYPHOIDAL SALMONELLA

6. Shigellosis Most common in children between 1-4yo
Present with high fever, abdominal cramps, watery diarrhea that becomes bloody and mucoid
Stool frequency is usually 8-10 per day
WBC can be normal or markedly elevated
Usually w/ high band count
Treatment
Antibiotics x 5 d eradicates organism from GI tract, reduces intensity and duration of illness, decreases spread
If acquired in US: Bactrim is 1st line
If acquired elsewhere: 3rd generation cephalosporin
Complications
Intestinal perforation, toxic megacolon, HUS, seizures, encephalopathy

7. Campylobacter Enterocolitis caused by C.jejuni or C.coli
Diarrhea, fever, abdominal pain, vomiting
50% with bloody stools
Febrile seizures may occur
Outbreaks common in children visiting dairy farms; organisms present in GI tracts of birds and animals
Neonatal infection
Acquired at time of birth ; Grossly bloody stools or fever may be only manifestation
Treatment
Most cases resolve spontaneously within 2 weeks
Azithromycin x 3-5 days eliminates the organism from the stool in 2-3d
Complications
Acute: Cholecystitis, Peritonitis, Rash, Septic pseudoaneurysm
Late: Reactive Arthritis, Guillain Barre Syndrome

8. E.coli Enterotoxigenic E.coli (ETEC) “Traveler’s Diarrhea”
Watery diarrhea in children
One of the most common bacterial causes of dehydration in children < 2yo in developing countries
Often causes diarrhea in travelers to tropical regions
Treatment: supportive; antibiotics shortens disease duration to 1 day
Enteropathogenic E.coli (EPEC)
Diarrheal illness most common in children < 6mo
Diagnosis via PCR
Enterohemorrhagic E.coli (EHEC)
Shiga toxin producing
E.coli O157:H7 is associated with HUS
Responsible for outbreaks of bloody diarrhea
Early antibiotic administration is assoc. w/ increased risk of HUS (?enhanced toxin release as bacteria are killed)

9. Yersinia enterolitica
Associated with bloody stools in 25% of patients
Presentation: fever and diarrhea
Stool usually contains WBCs, blood and mucus
Causes acute ileitis—mimics appendicitis and Crohn’s disease
Main reservoir in US is swine, most infectious occur after ingestion of raw or improperly prepared food
Includes unpasteurized milk
Treatment
Most cases spontaneously resolve within 2 weeks
No known benefit of antibiotics except for reduced excretion
Bactrim, Cefotaxime, Aminoglycosides are recommended choices

10. Clostridium difficile
Usually occurs after exposure to antibiotics
Especially ampicillin, clindamycin and cephalosporins
Varies from mild diarrhea to dysenteric syndrome
Diagnosis
Detection of C.difficile toxin by ELISA in stool
Stool culture does not differentiate toxin from non-toxin producing strains, and up to 50% of healthy infants can be colonized
Treatment
Antibiotics should be stopped or changed
If diarrhea persists or toxicity is present, PO flagyl or vancomycin is indicated for 7-10 days
IV flagyl can be considered in severely ill patient (No IV Vanco)

11. Cryptosporidium
Most common parasitic cause of acute foodborne diarrhea in US
Intracellular protozoan parasiteinterferes with intestinal absorption/secretionsecretory diarrhea
More common in children 1-9yo
Immunocompetent hosts: severely dehydrating, but self-limited diarrheal illness
Diarrhea, malaise, nausea, anorexia, crampy abdominal pain, fever
Fecal WBCs or blood rare
Immunocompromised hosts: life-threatening illness
Fecal-oral transmission (ingestion of oocysts), waterborne outbreaks
Diagnosis: microscopic examination of stool
Treatment
Supportive
Resolves without therapy in days in normal hosts
**Esp dangerous in patients with HIV

12. Giardiasis Diagnosis: stool microscopy
Giardia lamblia is flagellated protozoan parasite
Seen in daycare center outbreaks, illness in international travelers
Children < 5yo have highest rates of infection
Transmitted via fecal-oral, water, food, sexual intercourse
Diarrhea sudden in onset, watery, foul smelling w/ steatorrhea
Assoc w/ abd cramps, malaise, weight loss
Symptoms can last up to 4 wks
Diagnosis: stool microscopy
Treatment: all symptomatic patients
Metronidazole, Tinidazole, Nitazoxanide
**giardia cysts survive readily in mountain streamsgiardiasis is important cause of diarrheal illness in hikers
Giardia trophozoite

13. Rotavirus
Most commonly recognized viral pathogen of diarrheal disease in children
Makes up 30-70% of hospitalizations for AGE
Stools are watery or yellow without mucus or blood
Minimal to moderate fecal WBCs are seen in 30%
Higher incidence of vomiting and fever
Respiratory symptoms seen in 30-50%
Associated with more severe dehydration than other viral gastroenteritis
Detected in 25-30% of preschool age children who require hospitalization for diarrhea, vomiting and/or fever
Treatment
Supportive
Preventive: Rotavirus oral live vaccine at 2, 4, 6 mos

14. Adenovirus Makes up 5-10% of hospitalizations for AGE
Serotypes 40 and 41 cause AGE; these strains DO NOT cause respiratory symptoms
Average age of illness is 1-2yrs
Incubation period 8-10d, symptoms last 5-12d
Diarrhea + vomiting and fever
No seasonality
Treatment
Supportive

15. Norovirus
Transmission mainly via fecal-oral route, but airborne transmission can occur
Outbreaks in daycare, schools
Illness varies from mild febrile illness with watery diarrhea to more severe with vomiting, headache and constitutional symptoms
Incubation period is 24-48hrs, abrupt onset of symptoms, course lasts < 48hrs
Most present with both vomiting and diarrhea
Stools are usually non-bloody, non-mucusy, lack fecal WBCs
Fever present in 50%

16. Question #1
A previously healthy 17yo F presents to your office with 2 days of diarrhea associated with bleeding and tenesmus. She denies any history of abdominal pain, fevers, joint pains, constipation or weight loss. Growth and development are normal. She is in HS, lives at home with her parents and 1 male sibling and she volunteers 2 afternoons each week at an animal shelter. Fam Hx indicates that her mother has idiopathic ulcerative colitis and is being treated for a recent symptomatic flare. PE demonstrates a somewhat uncomfortable young woman with HR 80, BP 100/70. Abdomen is soft, non-distended without organomegaly, and there is moderate, direct tenderness in LLQ. Rectal exam demonstrates moderate tenderness and produces mucus streaked with gross blood.

17. Question #1 Of the following, the MOST likely cause of her illness is:
A. Campylobacter jejuni infection
B. Clostridium difficile infection
C. Entamoeba histolytica infection
D. Escherichia coli O157:H7 infection
E. Shigella dysenteriae infection
Symptoms of colitis: hematochezia, tenesmus
Campylobacter found in GI tract of animals (domestic and wild poultry, dogs, cats), dogs have been implicated in transmission, in kennel environments
C. diff: MCC of antibiotic associated colitis
Entamoeba infection is rare cause of infectious colitis in US
E.coli can be assoc w/ petting zoos, usually causes ENTERITIS
Shigella, often found in child care centers and areas with crowded living conditions

18. Question #2
A 10 week old, bottle-fed infant presents to your office on January 5th with bloody diarrhea and fever. There are no known sick contacts, although the family recently had a gathering on NYE and served chitterlings. The infant is febrile but appears well, and results of the PE are unremarkable. She has a diarrheal stool with a small amount of mucus and blood in it while you are examining her. The peripheral WBC is 15 with 70% PMNs, 20% lymphs, 10% monos. Hgb is 11 and platelets are 260.

19. Question #2
Of the following, the stool study MOST likely to establish the diagnosis is:
A. a culture on routine media
B. a culture on selective media
C. a polymerase chain reaction assay
D. a toxin assay
E. an ova and parasite assay
Chitterlings = pork intestines
Diarrhea likely caused by Yersinia enterocolitica, diagnosis must be established by sending a stool culture to be processed on selective media (CIN agar)
Routine stool culture detects Salmonella, Shigella, pathogenic E.coli
Right answer; infant likely infected when hands of caregivers are contaminated and not washed prior to handling infant
PCR is not commercially available
Toxin assay is for C.diff; since 50% of healthy infants can be colonized with C.diff, stool toxin assay would not be helpful
Bottle fed infant would be unlikely to have been exposed to a parasite