Gastrointestinal System Infections

Gastroenteritis

-Inflammatory process of the stomach or intestinal mucosal surface

-Associated with ingestion of contaminatd foods, water, poor sanitation/hygiene

-Infections vs intoxications

How many Canadians experience some food-related illness per year?

~4 million

Gastroenteritis- Infection

-Pathogen gains entry into GI tract; survive microbial antagonism

-Delay in appearance of GI symptoms (generally 1-3 days), while pathogen increases in sufficient numbers to cause damage

-Associated with fever

Gastroenteritis- Intoxication

-Associated with the ingestion of preformed toxin (exotoxin)

-Characterized by a sudden appearance of symptoms

~2-10 hours after consumption of the toxin

-Fever rarely a symptom

What is gastroenteritis characterized by?

-Abdominal pain/cramping

-Diarrhea

-Nausea and vomiting

-Dehydration, weight loss, fatigue

-Fever

-Acute diarrhea (<2 weeks)

Acute diarrhea

-Increased frequency of stools (more than 3 BM/day)

-Increased stool volume (>200 mL of fluid/day excreted in feces)

-Stools take the shape of their container; they are not formed

Non-inflammatory (secretory) diarrhea (Type I)

-Most common diarrheal syndrome in North America

-Typically caused by viruses e.g., norovirus, rotavirus

-More severe cases caused by bacteria (e.g., enterotoxigenic E.coli, Vibrio Cholerae)

-Associated with some parasites e.g., Giardia intestinalis

-Characterized by infection leading to large columes of watery diarrhea

Inflammatory diarrhea (Type II)

-Typically caused by bacteria that invade intestinal epithelial cells (e.g., damage intestinal wall)

-E.g., Shigella spp., Salmonella enterica, Campylobacter jejuni

-Characterized by frequent, small volume, loose stools

-Blood (gross or occult) often present, mucous and/or pus

Invasive diarrhea (Type III)

-Subset of inflammatory diarrhea associated with increased risk of bacteremia

-E.g., some Salmonella spp., enterohemorrhagic E.coli

Gastroenteritis- patient history

-Focus on disease severity and risk factors for significant disease

-Symptom duration; fever, abdominal pain, nausea, vomiting, dehydration and fatigue

-Description of diarrhea especially important to diagnosis (frequency, volume, visible blood, pus or mucous)

-Investigate potential for common source outbreak

-Inquire about friends and relatives with similar symptoms

-Travel history and recent antibiotic use

Physician consultation advised in all patients with any of the following symptoms:

-Fever (>38.5)

-Significant abdominal pain

-Dehydration

-Diarrhea persisting more than 7 days

-Visible blood and mucus/pus in stool

Short incubation period of gastroenteritis suggests what?

Ingestion of preformed toxin

Viral infection or food poisoning should be considered when _______ is a dominant symptom

Vomiting

Common incubation periods

Staphylococcal food poisoning 2-4 hours

Norovirus 12-48 hours

Salmonellosis 8-18 hours

E.coli O157:H7 1-3 days

Shigellosis 1-7 days

ETEC 1-3 days

Campylobacteriosis 2-5 days

Giardiasis 7-10 days

Risk factors for clinically significant disease (gastroenteritis)

-Age over 70

-Neonates

-Recent travel or camping

-Recent antibiotic use

-Immunosuppression (e.g., glucocorticoids, chemotherapy, etc.)

Gastroenteritis- physical exam

-Used to establish severity of disease; level of dehydration is especially important

-Decreased skin turgor

-Dry mucous membranes

-Tachycardia

-Orthostatic hypotension

Gastroenteritis infection- bacteria

-Cultures and/or multiplex PCR should be performed for patients with severe or persistent disease (>1 week)

-Not recommended if patient admitted for >72 hours, as likely C.difficile

Gastroenteritis infection- protozoa and helminths

-Studies for ova and parasites (and now parasite PCR) indicated in cases of persistent diarrhea despite antibiotic therapy, exposure to infants in daycare centres, international or wilderness travel, immunosuppression, raw fish consumption

-3 specimens may need to be collected on 3 separate days for O&P examination

Diarrhea

-Acute diarrhea is also associated with other conditions/disease states

-May represent the initial presentation of noninfectious and potentially life-threatening disease

-IBS, bowel obstruction, GI hemorrhage

-Medications can also cause diarrhea (metformin, colchicine, diuretics, ACE inhibitors, PPIs, magnesium containing antacids, antibiotics)

-A broad differential diagnosis should be considered upon initial investigation

What % of acute diarrhea are caused by GI infections or intoxications?

More than 90% of cases

Gastroenteritis management

-Rehydration; focus of initial managment

-Goal; to pass relatively dilute urine every 2-4 hours

-Oral fluids (e.g., water, pedialyte) and table salt usually sufficient

-IV fluids recommended in cases of severe dehydration or persistent emesis

-Patients should eat judiciously until stools are formed

-Agents to control diarrhea should only be used in cases of non-inflammatory (secretory) diarrhea (bulking agents, bismuth compounds, antimotility drugs e.g., loperamide)

-Antimicrobial therapy typcially reserved for severe cases of infectious gastroenteritis

Gastroenteritis infection control

-Transmission; oral route (contaminated hands, food, water)

-Routine practices and contact precautions (pediatric or incontinent)

-Case notification and outbreak notification

-Source control to prevent new cases

Bacterial gastroenteritis- Campylobacter jejuni

-Gram negative, helical shaped bacteria; possess a capsule and flagellum; invade and damage intestinal epithelial cells

-Infection characterized by: fever, abdominal pain and cramping, malaise, blood streaked, inflammatory diarrhea (>10 BM per day)

-Symptoms typically resolve within 1 week

Leading cause of foodborne illness in North America

Campylobacter jejuni

~80% of retail chicken in contaminated with C.jejuni

~60% of cattle excrete the bacterium in feces and milk

Campylobacter jejuni transmission and treatment

-Transmission: ingestion of contaminated food & water, contact with animal feces

-Infectious dose: 500-800 microorganisms

-Antibiotic treatment in cases of severe illness or those at risk of severe illness and outcomes

-Associated with post-infection sequelae; Guillain-Barre syndrome and reactive arthritis

-Infection control (community): good hand hygiene after handling raw poultry, dog, and cat feces, proper refrigeration to prevent increases in bacterial numbers, pasteurization of milk and chlorination of water supply

Bacterial gastroenteritis- Salmonella enterica

-Gram negative, bacillus; invades and multiplies within intestinal mucosa

-Typhoid (enteric) fever (Typhi & Paratyphi serotypes):

-Salmonellosis (enteritidis & Tphimurium serotypes)

Salmonellosis

-Acute infection characterized by: abdominal pain and cramps, chills, fever, nausea, loss of appetite, headache, myalgias, malaise, inflammatory diarrhea (negative for blood in most cases)

-Symptoms typically resolve within a week, require supportive therapy only; antibiotics reserved for severe cases (e.g., bacteremia)

-Transmission: ingestion of contaminated food and water; raw or undercooked meats, eggs, raw fruits and vegetables, seafood. Fecal-oral route: people and pets

Salmonellosis infection control (community)

-Good sanitation practices to deter food contamination

-Proper refrigeration to prevent increases in bacterial numbers

-Avoid cross-contamination of uncooked foods with raw foods that may contain Salmonella enteritidis or Salmonella typhimurium

-Good hand hygiene after handling animals

Typhoid (enteric) fever (Typhi & Paratyphi serotypes)

-Transmitted from person to person, vaccine preventable

-Progressively high fevers, stomach pain, diarrhea, rash, headache, muscle aches, chills, cough, loss of appetite

Bacterial gastroenteritis: enterotoxigenic E. coli (ETEC)

-Gram-negative, bacillus

-Produces an enterotoxin (exotoxin) similar to Vibrio Cholerae

-Commonly referred to as "Traveler's Diarrhea"

-Infection characterized by: watery, non-inflammatory diarrhea, 4-5 loose/watery stools per day, abdominal cramps, bloating, nausea and vomiting, fever

-Symptoms typically resolve in 3-4 days

-Transmission: ingestion of contaminated food, water and ice (human or animal feces)

-In severe cases, patients experience dehydration, blood stools, persistent vomiting, and high fever (>38.9 C), antibiotics reserved for these cases

-Infection control: "boil it, cook it, peel it, or forget it", avoid consuming non-sterile sources of water

Dukoral oral vaccine

-Adults and children at least 2 years of age

-Contains killed V.Cholerae and attenuated V.Cholerae enterotoxin

-Confers 3 months of protection, dosing should be initiated at least 2 weeks before their trip departure to protect against ETEC

-Can also be used for protection against cholera (timelines for administration change for some age groups)

Enterohemorrhagic E.coli (EHEC)

-E.Coli 01 57:H7 is the most common strain circulating in Canada

-Produces a verocytotoxin (aka shiga toxin) that damages intestinal mucosa, causing lesions and bleeding; microbe can attach to neutrophils and then travel throughout the bloodstream

-Infection characterized by: low-grade fever (30% of patients), abdominal cramping, pain and tenderness, inflammatory diarrhea (10 or more BM/day), infection progresses to hemorrhagic colitis 40-60% of patients (within 24 hours)

-In healthy adults, symptoms resolve within 1 week

-Transmission: contaminated raw milk, water, fruit juice, undercooked ground beef, and produce (spinich, sprouts). Person-to person (fecal-oral)

-Infection control (community): avoid consuming non-sterile sources of food and water, observe public health notifications related to contaminated foods, proper cooking of contaminated meats

Hemolytic Uremic Syndrome (HUS)

-Complication of EHEC

-Fever, abdominal pain, pale skin tone, fatigue and irritability

-Unexaplained small bruises or bleeding from nose and mouth, decreased urination, swelling of face, hands, and feet

-Destruction of RBCs, low platelts, acute kidney injury

-Complications occuring in 5-15% of cases (extremes of age most vulnerable), occurs 5-10 days after symptom onset

-Toxin (verocytotoxin/shiga) damages endothelial cells of small vessels in the kidneys; triggers clot formation and obstruction of the glomeruli resulting in acute kidney failure

-Risk aggravated by anti-motility drugs and antibiotics

-Treatment: IV fluids/electrolytes, red blood cell and platelet transfusions, kidney dialysis (required in 50% of patients)

Leading cause of acute kidney failure in children

Hemolytic uremic syndrome from EHEC

-Most cases resolve with no long-term sequelae

Shigella spp.

-Gram negative bacillus, closely related to E.coli

-S.Sonnei most common species in North America

-Children between 2-4 most susceptible

-Produce invasins, and an enterotoxin similar to V.Cholerae

-Transmission: contaminated food and water, person to person (fecal-oral)

-Associated with poor hygienic conditions (institutions) and overcrowding

-Infectious dose 10-100 organisms

Shigellosis

-Inflammatory diarrhea; often bloody and watery, but may contain pus and mucous

-Abdominal cramps, rectal pain, fever, nausea

-Symptoms typically resolve in 2-3 days, carrier status ~4 weeks

-Antibiotic treatment reserved in severe cases only

-Infection control; good sanitation practices to reduce food contamination & proper hygiene

Shigella dysenteriae

Severe purulent (mucous and pus) bloody stools; antibiotic therapy required; produces Shiga toxin/verocytotoxin similar to EHEC

Clostridioides difficile

-Gram positive anaerobic, endospore-forming bacillus

-Part of intestinal microbiome in 5% of adults (20-25% of older adults) and 50% of newborns

-Transmission through fecal-oral route

-Produce exotoxins that cause inflammation of the colon accompanied by increased fluid secretion and permeability of intestinal mucosa

-Enterotoxin (toxin A) and cytotoxin (toxin B)

Enterotoxin (Toxin A)

Diarrhea and inflammation

Cytotoxin (Toxin B)

Induces cell damage and facilitates lesion formation

C.diff antibiotic-associated diarrhea

-Suspect in any client who has diarrhea in association with broad-spectrum antibiotic exposure (<3 months of disease onset)

-Clindamycin, cephalosporins, broad-spectrum penicillins, and fluoroquinolones

-Typically associated with hospitals and nursing homes, but community cases increasing

-Symptoms include: 3-10+ watery stools in a 24-hour period, mild lower abdominal cramping and fever

-15% recover spontaneously with discontinuation of causative antibiotic

-Can advance to pseudomembranous colitis; life-threatening complication associated with declining host factors

Pseudomembranous colitis

-Complication of C.diff

->10 bloody stools per day (pus may be present), intestinal lesions (connective tissues, dying leukocytes, dead cells)

-On colonoscopy, the inflamed colonic mucosa contains small, raised, yellowish plaques

C. diff treatment

-Discontinuation of implicated antimicrobial agent and supportive therapy

-Vancomycin to treat C.diff if symptoms do not resolve

-Relapse in 20-30% of patients; for those that fail 2 rounds of antibiotic therapy may benefit from fecal microbiota transplant

C. diff complications

-Toxic megacolonl gross distension of colon causing the bowel wall to dilate and thin, increased risk of rupture

-Bowel perforation; due to damage to intestinal wall

C. diff infection control (hospital)

-Contact precautions and single room with a dedicated bathroom preferred

-Do not share equipment; ensure consistent environmental cleaning and disinfection

-Hand washing with soap and water preferred, due to absence of sporicidal activity in waterless antiseptic handwashes

Viral gastrointestinal infections commonly characterized by:

-Secretory diarrhea

-Abdominal cramping

-Nausea and vomiting

-Fever, chills & clammy skin

-Weight loss and lack of appetite

-Symptoms commonly appear within 24 hours of infection and resolve within 12-60 hours after symptom onset

Viral gastroenteritis

-Viruses infect epithelial cells of the intestinal tract where they undergo lytic replication

-As the host cell's die, the normal function of the GI tract is lost

-Self-limiting: once epithelial layer is destroyed, replacement cells grow, and function is restored

-Transmission: contaminated food and water (fecal-oral), person to person, aerosols from vomit

Viral gastroenteritis- Rotavirus

-Incubation period of 2-3 days

-Most common in children between 6 months and 2 years

-Prior to immunization, accounted for ~50% of cases of childhood diarrhea requiring hospitalization (due to dehydration)

-Symptoms persist (high fever, vomiting, diarrhea) for ~1 week

-Peak incidence in February-May

-Infection control (hospital): routine practices and contact precautions

-Infected children shed ~1000 organisms per gram of stool

Rotarix

-Oral vaccine for rotavirus

-PO, 2 doses at 2 and 4 months of age

Norovirus

-Leading cause of viral gastroenteritis; seasonality (November-April)

-Primarily transmitted through the fecal-oral route via direct contact or indirect through contaminated fomites, food and water, transmission via aerosolized vomit

-Infectious dose: ~10-100 viral particles, incubation period of 12-48 hours

-Symptoms include: secretory diarrhea, nausea & vomiting, stomach cramps, fatigue, low grade fever, chills, headache

-Symptoms persist for approx. 1-3 days

-Patients can shed asymptomatically for up to 14 days post resolution of symptoms

Norovirus diagnosis, infection control, and treatment

-PCR-based diagnostic panels increasingly available for clinical diagnosis

-Infection control: can live on hard surfaces for as long as 3 weeks, resistant to many disinfectants

-Hospital: routine practices and contact precautions, cohort affected patients to separate airspaces and toilet facilities

-Public: good hand hygiene is critical; wash hands with soap and water; hand sanitizer does not work well against norovirus

-Treatment: supportive

Intoxications

-Associated with the ingestion of preformed enterotoxin

-Enterotoxigenic strains of Staphlococcus aureus are the most common cause of intoxication in Canada

-Colonized food handlers shed the microbe from their skin and into food during preparation

-Often referred to as "food poisoning"

-Sudden onset of nausea, vomiting, abdominal cramps and diarrhea, in the absence of fever, suggests food poisoning

-Especially if symptoms present within 1-16 hours after exposure and resolve in less than 24 hours

-Self-limiting illness; fluid replacement (oral rehydration usually sufficient) in cases of mild dehydration, antemetic drugs

Intoxications- Staphylococcus aureus

-Gram positive cocci-shaped bacteria

-Strains produce an enterotoxin that is heat stable and can survive roughly 30 minutes of boiling

-Once toxin is formed, it cannot be destroyed- even if food is reheated

-Takes ~2 hours for bacteria to grow and secrete toxin in food

-Causes no obvious signs of spoilage or change in the food's taste

Foods commonly associated with intoxications

-Boiled and fried rice

-Undercooked meat and poultry dishes, soups and sauces (e.g., gravy)

-Processed meats, custard pastries, potato salad

-Inappropriately stored leftovers