14. Infections of the GI tract Flashcards
Healthy stomach features
sterile, contains only a few organisms because of low pH and enzymes
Healthy small intestine features
streptococci, lactobacilli and yeasts, the proportions of which depend on dietary habits
Healthy large intestine features
dense population of varied flora
* strep faecalis, bacteroides, enterobacteriaceae, clostridium spp, anaerobic streptococci
GASTROENTERITIS
1. What is it?
2. Symptoms?
3. Age and location prevalence?
1
Acute gastrointestinal illness usually due to infection
2
Vomiting and diarrhoea
Often associated with food poisoning
3
Can occur at all ages, but infants principal group
More common in countries with poor hygiene standards, water sanitation problems
Sporadic or epidemic forms
Diff bacteria incubation period and duration of symptoms?
Other causes of gastroenteritis (pathogen, type, incubation, duration)
- Not just cause by bacteria, also caused by pathogens
Risk groups FOR GASTROENTERITIS
- Enteric hygiene difficulties
- Pre-school, creche children
- Food workers
- Health care staff
CAMPYLOBACTER
- What is it?
- Symptoms
- Recurrent infection?
- How spread?
1
Commonest bacterial gastroenteritis in Western world - C. jejuni, C. coli
Curved, slender, Gram negative bacilli
2
Fever, myalgia, abdo pain, severe diarrhoea
Prolonged carriage can occur
3
Recurrent infection can occur in up to 25% of patients
Low infective dose
4
* Foods - poultry (gut of bird), raw milk and dairy products. May be contaminated by kittens and puppies.
* Caused by enterotoxin
CAMPYLOBACTER
- Diagnosis
- Treatment
- Post infection complications
1
Diagnosis - Selective media, low Ox, 43C.
* Gram, Biochemical.
2
Treatment - Erythromycin for prolonged symptoms or worsening symptoms, dysentery, pyrexia, bacteraemia, pregnant women and persons at risk for complications
3
Post-infectious complications, rare: * Guillain-Barre, RA, Convulsions
Prevention is key
SALMONELLOSIS
- How many serotypes?
- Incubation period?
- Symptoms
- Source?
1
2500 serotypes:
* S.enteritidis (non-typhoidal)
* S.typhi/S.paratyphi (typhoidal)
2
Incubation period- 1-2days
3
Nausea, vomiting, diarrhoea, fever, abdominal pain.
Disseminated sepsis
4
Source - ingestion of contaminated food/water
Found in domestic animals and poultry * Poultry, swine, cattle.
* Handling exotic pets- reptiles, turtles
SALMONELLOSIS
- Age
- Duration
- How
1
Infants, elderly, decreased stomach acid
2
Duration 1-7 days
3
Organisms enter gut mucosal cells and produce enterotoxin which acts in jejunum, ileum and colon.
Gastroenteritis - 75% of infections
Bacteremia - 5% to 10% of infections, often resulting in distant infections (eg, central nervous system infections, endocarditis, or osteomyelitis)
SALMONELLOSIS
- Diagnosis
- Treatment
- Second spread
1
Diagnosis - Enrichment and selective media
* Biochemical and serological
2
Treatment - Rehydration. Treatment rarely necessary (Antibiotic therapy is contraindicated- prolongs the carriage of the organism in the convalescent phase)
3
High secondary spread
* Strict contact precautions
* Clinical surveillance of contacts
STAPHYLOCOCCUS AUREUS
- Source?
- Symptoms
- Incubation
- Diagnosis
- Treatment
1
Foods - cooked food not stored at 4 degrees or frozen immediately is the main source of infection
Source - generally from food handler. Organisms multiply in warm conditions
Caused by preformed heat - stable enterotoxins
2
Nausea and vomiting (and diarrhoea in 25% of
patients)
3
Incubation 1⁄2 to 6 hours. Duration 1-24 hours, rarely 48 hours
4
Diagnosis - faecal culture
5
Treatment - self-limiting, no treatment required
BACILLUS CERUS
- what?
- Source
- Types
- Symptoms
- Treatment
1
Aerobic spore-forming gram-positive bacillus
2
Foods - mainly rice, also other cereals, raw, dried
and processed foods.
Spores survive boiling - sporulation
3
Two types of poisoning: Emetic and diarrhoeal (rare)
4
Symptoms usually occur within 2 to 6 hours after ingestion of contaminated food. Last 6 to 10 hours.
5
No treatment required, self-limiting
BACILLARY DYSENTERY (SHIGELLOSIS)
(Make Q’s)
- Shigella sonnei is the most common species in developed countries
- Other 3 species S flexneri, S boydii, S dysenteriae usually acquired abroad
- Mild intestinal illness - fever, malaise, self-limiting watery diarrhoea
- The diarrhoea may decrease and become bloody with mucus and pus (ie. dysentery)
- Requires low infecting dose acquired by direct contact
- Short incubation period- within 48 hours
- Is locally invasive in large bowel
BACILLARY DYSENTERY (SHIGELLOSIS)
diagnosis
Treatment
- S dysenteriae infection is most likely to cause complications such as HUS, dysentery, and toxic megacolon.
1
Diagnosis - isolate organism on selective culture media
2
Treatment - rehydration. Antibiotics indicated for most patients- ciprofloxacin
CRYPTOSPORIDIOSIS
- A self limiting diarrhoeal illness in children
- Nausea and vomiting
- Drinking contaminated water containing cysts of - Crypto parvum
- Source is infected cattle
- Very resistant to chlorination
- A more severe illness occurs in immunocompromised (AIDS)
- Diagnosed by finding cysts in stool (acid ‘fast’)
- No specific treatment
CLOSTRIDIUM PERFRINGENS
- Gas gangrene and food poisoning
- Heat resistant spores survive in contaminated foods during the heating procedure. After food is ingested- sporulation occurs in the GIT and an enterotoxin is produced
- Abdominal pain and watery diarrhoea
- Treatment - symptomatic, no antibiotics
- Prevention - good food hygiene, adequate cooking of food to kill the organisms
INFANTILE GASTROENTERITIS - principle causes
Viral
-rotavirus (the most common cause)
-noroviruses (Norwalk like)
Bacterial (Escherichia coli)
-enteropathogenic
-enterohaemorrhagic
-enterotoxigenic
-enteroinvasive
VIRAL GASTROENTERITIS
- Frequent cause of infantile gastroenteritis
- Up to 50% of cases caused by rotaviruses in under 3 year olds
- Short incubation of 2-4 days
- Presents as acute diarrhoea of mild to moderate severity, may be vomiting
- More common in winter months
- Diagnosed by detection of rotavirus antigen in stool
- Supportive care
ENTEROPATHOGENIC E COLI (EPEC)
- More than 20 (O) serotypes have been identified in outbreaks of infantile diarrhoea
- Spread by contaminated food
- Small intestine affected
- Local destruction of intestinal epithelial cells
- Infantile gastroenteritis, traveller’s diarrhoea
- Fever, nausea, vomiting, non-bloody stools
- Self-limiting, supportive care, no specific antibiotic treatment
ENTEROHEMORRHAGIC E COLI (EHEC)
- Enterohemorrhagic E coli (EHEC) produce Shiga toxin (STEC) or verotoxin (VTEC)
- Over 100 serogroups, 0157:H7 commonest.
- Diarrhoea, bloody colitis, HUS (5%).
- Haemolytic anaemia, thrombocytopenia, ARF.
- Ingestion of undercooked hamburger, salami,
- sprouts, and unpasteurized milk
- Low infective dose
- Antibiotics and antimotility agents should be avoided if EHEC infection is suspected clinically
ENTEROTOXIGENIC E COLI (ETEC)
- Common cause of diarrhoea in travellers and in children in developing countries.
- Organism attaches to the small bowel and causes diarrhoea through enterotoxins.
- Mild to severe watery diarrhoea, cramps
- Antibiotics (quinolones, TMPSMX, and rifaximin) often are given empirically for moderate to severe traveller’s diarrhoea
ENTEROINVASICE E COLI (EIEC)
- Fever, watery diarrhoea, cramps
- Develops to (bacillary) dysentery, bloody stools
- Large bowel affected, by invasion and local destruction of epithelial cells
- Not enteropathogenic serotypes or enterotoxin producers
GIARDIASIS
- Caused by Giardia lamblia
- Flagellate protozoan
- Ingestion of cysts in contaminated food or water (resists chlorination)
- These develop into trophozoites in duodenum
- Find cysts or rarely trophozoites in stool
- Symptoms of cramping abdo pain, flatulence, - diarrhoea
- Metronidazole is antimicrobial of choice
CLOSTRISIUM DIFFICILE
- Antibiotic associated pseudomembraneous colitis
- Antibiotics (clindamycin, cephalosporins) suppress normal flora, C. diff to multiply, produce toxins
- Yellow ‘pseudomembranes’
- Normal commensal in 3 % population
- 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
AMOEBIC DYSENTERY
- Causative organism: Entamoeba histolytica
- Indian sub Continent, Africa (but Worldwide
distribution) - Acquired from eating food contaminated with cysts
- Can be severe diarrhoea with blood and mucus in stool
- Can progress to cause perforation of large bowel and peritonitis
- Also, liver involvement with hepatitis or liver abscess
- Treatment with metronidazole
CHOLERA
- Caused by Vibrio cholerae
- Typically water borne
- Infects only humans
- Short incubation period
- A severe diarrhoeal illness with ‘rice water’ stools +/- vomiting and nausea
- Dehydration, electrolyte loss, circulatory and renal failure
- Mortality 40% without treatment
- Treat by rehydration and antibiotics (tetracycline or ciprofloxacin)
HELICOBACTER PYLORI
- Chronic gastritis and gastroduodenal ulceration, some cases of gastric carcinoma
- Gram negative bacterium
- 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)
Prevention of 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 insects and other pests and vermin
- Handwashing and hygienic practices
