Infections of the GI Tract Flashcards
What does the normal microbiome look like for the stomach, SI, & LI?
Stomach- sterile, contains only a few organisms because of low pH and enzymes
SI- streptococci, lactobacilli and yeasts, the proportions of which depend on dietary habits
LI- dense population of varied flora: Strep faecalis, Bacteroides spp, enterobacteriaceae, Clostridium spp, anaerobic streptococci
What is gastroenteritis, what is associated with it, and who commonly gets it?
Acute gastrointestinal illness usually due to infection.
You get vomiting and diarrhoea and it’s often associated with food poisoning.
Can occur at all ages, but infants principal group
Where is gastroenteritis more common?
More common in countries with poor hygiene standards, water sanitation problems.
What are some bacterial causes of gastroenteritis and their individual incubation periods?
look at the slides
What are some other non-bacterial causes of gastroenteritis and their incubation periods?
There are also viral and parasitic causes.
look at the slides
What are the main groups at risk of contracting gastroenteritis?
-Enteric hygiene difficulties
-Pre-school, creche children
-Food workers
-Health care staff
What is the commonest bacterial gastroenteritis in the Western world?
Gastroenteritis secondary to Campylobacter, with C. jejuni & C. coli being some of the most common diarrhoea-inducing agents in the Western world.
What are the characteristics of campylobacter?
Curved, slender, Gram negative bacilli
What are the signs and symptoms associated with campylobacter gastroenteritis?
-Incubation period which can be up to 4 days.
-these can be fever, myalgia, myalgia abdominal pain, and headaches.
-Diarrhoea occurs later & ranges from profuse, watery stools to bloody stools lasting up to one week.
-Patients may have prolonged carriage, however a chronic carrier state is rare
Can recurrent infection of campylobacter gastroenteritis occur?
Yes, in up to 25% of patients
Where can campylobacter be found?
In the gut or oral cavity
common sources are food (poultry; gut of bird), raw milk and dairy products
It can also infect young animals, like kittens or puppies, and then spread to humans
Caused by enterotoxins
How do you diagnose campylobacter gastroenteritis?
Via stool culture
Selective media, low Ox, 43C
Is treatment required for campylobacter gastroenteritis?
Not normally since it’s a self limiting infection
Erythromycin recommended for symptoms lasting more than 1 week
OR
If patient presents with worsening symptoms, dysentery, pyrexia, bacteraemia, is pregnant, or at risk of complications
(extremely young or elderly, immunocompromised, or those with liver cirrhosis)
Are there any post-infectious complications with campylobacter gastroenteritis?
Infection caused by salmonella bacteria.
This can cause a spectrum of diseases which can be divided into:
non-typhoidal types (causing self-limiting gastroenteritis)
typhoidal subtypes (like salmonella typhi, and salmonella paratyphi, which can cause typhoid fever)
What is the incubation period, symptoms & signs, and source of salmonellosis (non-typhoid)?
Incubation period : 1-2 days
Symptoms: Nausea, vomiting, diarrhoea, fever, abdominal pain and disseminated sepsis (severe sepsis)
Source: ingestion of contaminated food/water.
Also found in domestic animals and poultry e.g poultry, swine, cattle
Or from handling exotic pets
How long do the conditions caused by salmonella last and what are the possible outcomes?
Duration: 1-7 days
Gastroenteritis occurs in 75% of infections
Bacteraemia occurs in 5-10% of infections, often resulting in distant infections (e.g. CNS infections, endocarditis, or osteomyelitis)
Which groups are mostly affected by salmonella?
Infants, elderly and those with decreased stomach acid
How do you diagnose salmonella?
Stool culture
Enrichment and selective media
What is the treatment for salmonella infections?
Rehydration (treatment rarely necessary and antibiotic therapy is generally contraindicated as it would prolong the carriage of the organism in the convalescent phase and cause resistance)
Antibiotic therapy is only indicated for those with colitis, bacteraemia, haemoglobinopathies & immunocompromised states
Does salmonella have a high secondary spread?
Yes so it’s important to have strict contact precautions & clinical surveillance of contacts.
Describe the sources, and symptoms of Staphylococcus aureus.
Staphylococcus aureus - bacteria that can cause a range of infections of the skin, bone and heart valves.
When infected, it can cause nausea, vomiting and diarrhoea (25% of cases)
Usually due to cooked food not stored at 4 degrees/frozen immediately + food handler since organisms multiply in warm conditions
What is the incubation/duration period of staphylococcus aureus? What treatment is given?
Incubation: 1/2 - 6 hours.
Duration: 1-24 hrs (rarely 48)
Treatment: self-limiting, no treatment required
What is Bacillus cereus?
Aerobic spore-forming gram-positive bacillus which can contaminate foods such as rice, cereals, raw, dried & processed foods
It survives cooking/boiling by sporulation
What does the Bacillus cereus toxin cause?
Two types of poisoning: emetic (vomiting) and diarrhoeal (rare)
Symptoms (nausea & vomiting) usually occur within 2 to 6 hours after ingestion of contaminated food
Symptoms can last for 6 to 10 hours
No treatment required; self limiting
How can you prevent Bacillus cereus infection?
Adequate food hygiene & correct storage of food.
What is Shigellosis and what can it cause?
Most common species in developed countries producing mildest symptoms.
Due to contaminated food + water
Causes fever, malaise, self-limiting eatery diarrhoea (can have mucus, pus and blood)
Incubation: 48hrs
Locally invasive in large bowel
Which species of Shigella is most likely to cause complications and how do you diagnose & treat this?
S. dysenteriae infection is most likely to cause complications such as HUS, dysentery, and toxic megacolon
Diagnosis- isolate organism on selective culture media
Treatment- rehydration
Antibiotics indicated for most patients- ciprofloxacin
What is cryptosporidiosis?
A self limiting diarrhoeal illness in children that causes nausea & vomiting.
How is cryptosporidiosis acquired?
By drinking contaminated water containing cysts of Crypto parvum found in infected cattle or humans and passed on in stools.
Why is elimination of cryptosporidiosis difficult?
Because it’s very resistant to chlorination
A more severe illness results in those that are immunocompromised e.g. like in those that have AIDS
How is cryptosporidiosis diagnosed?
By finding cysts in stool (acid ‘fast’)
There is no specific treatment
What is Clostridium perfringens responsible for?
Gas gangrene and food poisoning
How is Clostridium perfringens transmitted?
Heat resistant spores survive in contaminated foods during the heating procedure
After food is ingested- sporulation occurs in the GUT and an enterotoxin is produced
Also contamination of an open wound
What are the symptoms, treatment, and prevention of Clostridium perfringens?
Symptoms- abdominal pain and watery diarrhoea
Treatment- symptomatic, no antibiotics
Prevention- good food hygiene, adequate cooking of food to kill the organisms
What are the principal causes of infantile gastroenteritis?
Viral:
-rotavirus (the most common cause)
-noroviruses (Norwalk like)
Bacterial:
Escherichia coli
Different strains are classified based on their serological and virulence properties:
enteropathogenic; enterohaemorrhagic; enterotoxigenic; enteroinvasive
What is the incubation period of viral gastroenteritis and what are the symptoms?
-Incubation period: 2-4 days
-Presents as acute diarrhoea of mild to moderate severity, may be vomiting
-Common in winter months
How is viral gastroenteritis diagnosed & treated?
Diagnosed by detection of rotavirus antigen in stool.
Treatment is supportive care as medication not necessary.
What can enteropathogenic E. coli cause (EPEC)?
More than 20 (O) serotypes have been identified in outbreaks of infantile diarrhoea.
What can EPEC affect, how is it spread, and what are the symptoms, and how do you treat it?
Small intestine affected (local destruction of intestinal epithelial cells)
Spread by contaminated food
Symptoms include fever, nausea, vomiting, non-bloody stools
Self-limiting, supportive care, no specific antibiotic treatment
What 2 types of diarrhoea can EPEC cause?
Infantile gastroenteritis (acute & profuse)
traveller’s diarrhoea (accompanied by abdominal pain & vomiting)
Both produce NON-BLOODY stools
Organism attaches to the small bowel and causes diarrhoea through enterotoxins
What does enterohaemorrhagic E. coli (EHEC) produce?
Shiga toxin (STEC) or verotoxin (VTEC)
These ultimately cause colitis after an incubation period of 3-5 days
What is the most common strain of EHEC & what does it cause?
O157:H7
Diarrhoea, bloody colitis, HUS (5%)
How can EHEC infection occur and how should you treat it?
Ingestion of undercooked hamburger, salami, sprouts, and unpasteurised milk
Antibiotics and antimotility agents should be avoided if EHEC infection is suspected clinically
What symptoms are associated with ETEC and how is it treated?
Ranges from mild to severe watery diarrhoea, cramps
Rehydration is main state of therapy
Antibiotics (quinolones, TMPSMX, and rifaximin) often are given empirically for moderate to severe traveller’s diarrhoea
What symptoms does enteroinvasive E. coli (EIEC) cause and how does it affect the body?
Fever, watery diarrhoea, cramps
(Rarely) develops to (bacillary) dysentery, bloody stools
Large bowel affected, by invasion and local destruction of epithelial cells
What is giardiasis?
SI infection caused by the flagellate protozoan Giardia lamblia.
How is giardiasis acquired?
Ingestion of cysts in contaminated food or water (resists chlorination)
These develop into trophozoites in duodenum
Find cysts or rarely trophozoites in stool
What symptoms do you get with giardiasis and when do they occur?
Symptoms present 1-2 weeks after ingestion and include cramping abdominal pain, flatulence, diarrhoea.
What is the antimicrobial of choice in giardiasis?
Metronidazole
What is Clostridium difficile (C. diff)?
Antibiotic associated pseudomembraneous colitis:
antibiotics (clindamycin, cephalosporins) suppress normal flora, C. diff multiplies, produces 2 toxins (cytotoxin and enterotoxin)
1st toxin binds to mucosal receptors causing cytotoxicity and inducing apoptosis.
2nd toxin enters the damaged mucosa causing further toxicity which leads to inflammation, haemorrhage etc
How do you diagnose, treat & prevent C. diff?
Diagnosis- sigmoidoscopy, toxin in stool samples
Treatment- withdraw offending antibiotic, replace fluids, metronidazole, oral vancomycin
Prevention– wash hands/surfaces, selective use of antibiotics, isolate infected patients
What is the causative organism of amoebic dysentery?
Entamoeba histolytica
Where is ameobic dysentery common and how can it be acquired?
Indian sub Continent, Africa (but Worldwide distribution).
Acquired from eating food contaminated with cysts
What are the symptoms associated with amoebic dysentery and how can it affect the body?
90% of individuals have no symptoms, but for the remaining 10%:
Can be severe diarrhoea with blood and mucus in stool
Can progress to cause perforation of large bowel and peritonitis
Also, you can have liver involvement with hepatitis or liver abscess
What is the treatment for amoebic dysentery?
Metronidazole
What is cholera caused by and how does it spread?
Caused by Vibrio cholerae and it’s typically water borne & infects only humans
It also has a short incubation period
What is cholera and what can it cause?
A severe diarrhoeal illness with ‘rice water’ stools +/- vomiting and nausea
Can cause dehydration, electrolyte loss, circulatory and renal failure
What is the mortality rate for cholera without treatment?
40%
How do you diagnose and treat cholera?
Diagnosis with faecal culture
Treat by rehydration and antibiotics (tetracycline or ciprofloxacin)
What may Helicobacter pylori infection give rise to?
Chronic gastritis and gastroduodenal ulceration, some cases of gastric carcinoma.
What is H. pylori?
Gram negative bacterium
How is H. pylori treated?
Treatment of H. pylori infection usually involves 7 days’ therapy with two antibiotics: (clarithromycin, metronidazole, and amoxicillin are often used)
together with a proton pump inhibitor (omeprazole)
Treatment fails in 10% of patients because of drug resistance
How can we prevent foodborne illnesses?
Recognition of possible sources
Thorough cooking of food
Segregation of foodstuffs
Rapid cooling and good refrigeration
Store food so as to prevent multiplication
Treatment of foods likely to be contaminated
Exclusion of infections and other pests/vermin
Handwashing and hygienic practises
