Lecture 18: Bacteria, Parasites and Toxin Mediated Gastroenteritis Flashcards
Rules for Avoiding Enteric Pathogens
“Cook it, boil it, peel it, or forget it”
Acute Gastroenteritis
Diarrheal disease of rapid onset, with or without accompanying symptoms that include nausea, vomiting, fever, or abdominal pain
Diarrhea
- Frequent passage of uninformed liquid stool (>3 or more loose watery stool per day)
Acute diarrhea: <14 days
Chronic diarrhea: >14 days
Dysentery
Blood or mucous in the stool
Bacterial Gastroenteritis
- Inflammation of GI tract due to bacteria
- Abdominal pain, bloody stool, loss of appetite, nausea and vomiting
Blood stool: associated with mucosal invasion of bacteria
Watery stool: no mucosal invasion - Typically bacterial gastroenteritis is associated with BBQ season
Acute Diarrhea (2 types)
Acute watery diarrhoea: most common, presents within 48hrs, usually self limiting, main complication is dehydration (rota, e. coli, vibrio cholera)
Acute bloody diarrhoea: passage of bloody stools, result of damage to intestinal mucosa by an invasive organism, complications like sepsis, malnutrition, and dehydration (shigella spp, entamoeba histolytica)
Viral Gastroenteritis
- small intestine
- watery diarrhea
- vomiting: +++ or +
- abdominal pain: + or -
- tenesmus: -
- anorexia: + or -
- systemic illness symptom: + or -
Bacterial Gastroenteritis
- colon
- blood, mucoid diarrhea
- vomiting: + or -
- abdominal pain: +++ or ++
- tenesmus: ++ or +
- anorexia: +++ or ++
- systemic illness symptom: +++ or ++
Bacterial Gastroenteritis Types
Salmonella
Campylobacter
Vibrio
Shigella
Bacterial Gastroenteritis Epidemiology
- one of most common causes of illness in children and adults
- acquired thru fecal-oral route, but contaminated water and food play a role
- age 3 children become infected by most common agents
- deaths usually a result of dehydration with episodes usually lasting 5-10 days
Pathophysiology of Enteric Pathogens
- alterations to natural defences of the body
- risk and disease associated with organism dose
- exposure to disease causing organism
Salmonella Risk Factors
- Gram -‘ve
- Majority of infections from beef, poultry, unpasteurized milk, unpasteurized eggs but any veg
- Inadequate thawing from freezing is a common source
- International travel
- reptiles carry salmonella in their gut
- stomach acid provides some protection
Clinically salmonella
- incubation period of 6-72 hrs
- usually tends to be relatively mild and self limiting
- under age of 2 + over age of 65 TREAT b/c increased risk
- diarrhea starts w fever, ab cramps, chills, myalgia, can be bloody, may be nausea or vomiting
- illness typically lasts 4-7 days and is usually self limiting
Pathogenesis of intestinal salmonella infection
- rapid invasion of GI mucosa following infection
xtra-intestinal salmonella
- called typhoid fever
- typically result of infection with salmonella typhi or salmonella paratyphi
- salmonella bacteria causes gastroenteritis can enter blood stream or body cavity by breaks in the intestinal wall
Treatment for Salmonella infections
- Intestinal salmonella spp.
- Often self limiting and does NOT need to be treated
- Treat with antibiotics for anyone <2 yrs or >65 yrs or immunocompromised
- ALWAYS treat xtra-intestinal Salmonella
- Starting to see increasing resistance
Shigella spp.
- Gram -‘ve bacilli
- Acquired via poultry, causes bloody stool
- Incubation of 1-7 days, with acute diarrhea in 1-2 days
- Organisms can be shed for up to 4 weeks after incubation
- Non motile bacteria
- Ingested pathogens can survive the gastric acidity and can cause illness by infection the colonic mucosa
Clinical presentation of Shigella spp.
- Sudden onset
- Initial symptoms include abdominal colic and cramps
- Progresses from watery diarrhea to bloody mucus filled stool
- Fever, headache, malaise and anorexia
Risk factors for Shigellosis
- Children in daycare centers
- International travelers
- Immunocompromised individuals
- Ppl living with inadequately tested water supply
Pathogenesis of Shigella spp.
- Significant proportion of damage is a result of host immune responses
- Bacteria also produce specific toxin that can lead to cell death
- Shiga toxin has 2 parts. Part B binds to cells and injects Part A which prevents protein synthesis and causes cell death
Pathogenesis of Shigella spp.
- Significant proportion of damage is a result of host immune responses
- Bacteria also produce specific toxin that can lead to cell death
- Shiga toxin has 2 parts. Part B binds to cells and injects Part A which prevents protein synthesis and causes cell death
Infection of Shigella spp.
- Hard to control outbreaks
- Ill patients and workers should not be allowed to return for at least 24 hrs
- Ppl should refrain from rec water venues for 1 week after symptoms resolve
Treatment/Prevention for Shigella spp.
- Most intestinal cases are self-limiting, mild cases doesn’t require antibiotics
- Severe cases should be treated with antimicrobials or in anyone that has underlying immunodeficiency
- Antibiotics can shorten duration of illness and to prevent the spread of infection
- Wash hands, ensure food is handled appropriately
E. coli diarrhea
- Gram -‘ve bacilli commonly in GI tract
- Specific pathotypes are associated with diarrhea NOT all E. coli produce infection
Risk factors for developing E. coli diarrhea
- E. coli with specific virulence factor
- Consumption of undercooked beef and unpasteurized foods
- Consumption of raw vegetables
- Visiting farms and/or working in farms
- Travel - common cause of “travellers diarrhea”
STEC
Hemolytic Uremic Syndrome (HUS) most often associated with E. coli (O157 has very BAD outcomes) O157:H7 but others also present
Complications with STEC infections
- Serious and typically develops 7 days after the onset the diarrhea
- More than 50% of children require dialysis and 3-5% of children will die
- HUS can develop neurologic complications
- HUS is associated with antibiotic therapy
Campylobacter spp.
- Gram -‘ve curved bacteria
- Diarrhea, abdominal pain, malaise and fever
- Incubation time usually 2-5 days can present with mild symptoms that last 1-2 days resembles viral gastroenteritis
Risk factors for Campylobacteriosis
- campylobacter spp is normal flora in chickens and wild birds
- improper cooking of poultry and unpasteurized eggs, milk and other animal products are all potential sources
- outbreaks are rare but happen
- transmission documents from mammalian pets
Pathogenesis of Campylobacter Infections
- Fever, abdominal pain, and cramps
- Bloody mucoid stool with minimal vomiting
- Self resolving w rehydration therapy
- Antimicrobial therapy is indicated for more serious presentations
Yersinia enterocolitica
- Gram -‘ve bacteria - only 3 are pathogens
- Yersinia enterocolitica causes age-specific syndromes presenting with fever, watery stool, abdominal pain, and acute lymphadenitis
- Major of all cases occur in children under age of 24 months
Pathogenesis of Yersinia enterocolitica
- Fecal-oral transmission from animals to humans
- Found in contaminated foods including pork, tofu, unpasteurized animal products
- Incubation is 4-6 days
- Tissue invasion associated w bloody diarrhea
- Mostly self-limiting
Toxin Mediated Gastroenteritis
- Rapid onset - diarrhea, vomiting, and abdominal cramps most common presentations
- Toxin pre-formed in food is heat stable and not sensitive to degradation
- Organisms produce toxins after ingestion
- Clostridium spp. produce spores which are resistant to stomach acids and cooking
Pathogenesis of Giardia
- Has a trough and cyst
- Very enviro stable
- Gets destroyed by stomach acid
- Infection is slight
- Lead to development of diarrhea, excess gas, stomach or abdominal cramps, nausea
- Transmission via the cyst
- Incubation period is 1-3 weeks
Detection/transmission and treatment of Giardia
- Contaminated water, hands, food, and other fomites
- Transmission by asympt carriers
- Some self-limiting and may require treatment but more serious infections should be treated with anti-parasitic drugs
- Ensure patients are not dehydrated
- Detection by EIA or PCR or ova/parasite detection
Entamoeba histolytica Gastroenteritis
- Syndromes include non-invasive intestinal amebiasis infection
- Can lead to liver abscess
- Gradual onset of symptoms over 1-3 weeks
- Offensive odour of stool simulating bacillary dysentery or ulcerative colitis
- Detection via ova/parasites, PCR, and antigen detection
Transmission/Epidemiology of Entamoeba histolytica
- Global, but common in lower socioeconomic status
- Transmitted via asympt. ppl and contaminated water
- Cysts once ingested are unaffected by gastric acid and lead to disease
- Can go for yrs without diagnoses
