Bacterial Causes of Gastroenteritis Flashcards
(12 cards)
What is Gastroenteritis?
What can cause gastroenteritis?
How do you treat it?
Inflammation of the gastrointestinal tract
Caused by ingesting contaminated food/water
Causes can be bacterial, viral, protozoal, non-infectious
Self-limiting; immediate concerns are dehydration + spread of infection
Symptoms of gastroenteritis
Vomiting
Abdominal pain
Diarrhoea
What are the major bacterial + viral causes of gastroenteritis?
Rotavirus + Norovirus are the most common viral cause of gastroenteritis.
Campylobacter is the most common bacterial cause of gastroenteritis.
What is campylobacter?
Why is it hard to culture?
What are the main strains that cause gastrointestinal disease in the UK?
How is it transmitted?
How can bacteria be killed?
What do most strains produce?
How can it be treated?
How long does it take for gastroenteritis to occur after infection?
Gram-negative proteobacteria of the class
Epsilon-proteobacteria (like Helicobacter) that cause infective bacterial food poisoning
Hard to culture because it is microaerophillic (it requires an environment that contains a reduced concentration of oxygen)
Pathogenic strains are motile (can move)
C.jejuni + C.coli are the main bacterial causes of gastrointestinal disease in the UK\
Infection can be transmitted through ingesting contaminated water/food containing faecal matter or ingesting raw meat/unpasteurised milk
Easily killed by cooking
Most pathogenic strains produce a cytolethal distending toxin, a DNA cleaving protein complex which stops mammalian cell division + delays activation of an immune response
Treated with ciprofloxacin/erythromycin
Causes gastroenteritis 3-5 days after infection
What is Salmonella enterica?
How many serotypes are there? + what are the most common ones?
How long is the incubation time?
What are the common symptoms?
How long do most pts recover?
What happens with salmonella enters bloodstream? + how can this be treated?
A motile Gram-negative bacterium of the Proteobacteria, class Gammaproteobacteria, related to Escherichia coli
Causes infective bacterial food poisoning
2000 serotypes of Salmonella
Serotypes Enteriditis + Typhimurium are the most common
Infections are due to contamination from animal faeces (including pets). Common in eggs + poultry. Can proliferate fast in food.
Incubation time = 0.5 - 3 days
Symptoms include fever, abdominal pain, non-bloody diarrhoea + muscle pain + vomiting
Most pts recover in 7 days
Strict hygiene should be practised + food prep. by infected pts avoided.
Bacteria can enter bloodstream + cause localised infections in the body = bacteraemia.
Treated with ciprofloxacin/cefotaxime
What strain of Salmonella causes typhoid fever?
How can it be contracted?
What are the symptoms of typhoid fever?
How does the bacteria travel through the body?
Salmonella enterica Typhi
Only be contracted from ingesting human faeces
Infectious = only need small amounts of strain
Causes fever, cramps + diarrhoea
Bacteria travel in the blood inside phagocytic cells to the spleen, bone marrow, liver + gall bladder. The gall bladder can cause re-infection of the gut.
What type of bacteria is E.coli?
Where are the commensal strains present?
What do the pathogenic strains cause?
How do you distinguish commensal from pathogenic?
How long is the incubation period for gastroenteritis caused by E.coli?
What is the main symptom of gastroenteritis caused by E.coli?
How do you treat it?
Motile gram-negative bacterium, proteobacteria, class gammaproteobacteria
Commensal strains are present in the large intestine
Pathogenic strains can cause septicaemia, UTI, neonatal meningitis + gastroenteritis
Distinguish commensal from pathogenic strains by serotyping their O, H + K antigens
Gastroenteritis caused by E.coli has an incubation period of 1 - 3 days after ingesting large numbers.
Main symptom = diarrhoea
Disease is self-limiting - rehydration
Infection with the most aggressive strain can be mistaken for appendicitis + lead to haemolytic-uremic syndrome = characterised by vomiting, bloody diarrhoea + blood in the urine
E.coli gastrointestinal infections are traced to water contaminated with faeces
Virulence factors + antibiotics resistance genes are carried on plasmids + phages so horizontal gene transfer plays a large role in the development of pathogenic strains
What is Shigella?
What disease does shigella cause?
What are the symptoms of shigellosis?
How long is incubation?
What is the most severe strain?
How is severe strains treated?
Non-motile gram-negative genus of proteobacteria, class gammaproteobacteria
Closely related to E.coli
All species of shigella can cause shigellosis disease
Symptoms of shigellosis include acute abdominal pain, fever, mucus/bloody diarrhoea (dysentry)
Incubation = 1-7 days
Complete recovery takes 1-2 weeks
Shigella is not affected by stomach acid
Very infectious
Shigella is the most common form of dysentry in the UK
Severe strain = Shigella dysenteriae - secretes shiga toxin
Treated with ciprofloxacin
Plasmid mediated Beta-lactamase antibiotic resistance is common
What is vibrio?
What strain of vibrio causes cholera?
When do symptoms start to show + what are they?
How do you pass the infection?
What is the main treatment + antibiotic treatment?
A genus of motile gram-negative of the proteobacteria
Most vibrio strains cause disease by the ingestion of raw infected shellfish causing vomiting + diarrhoea
Vibrio cholerae strains O1 + O139 secrete cholera toxin + cause cholera by inducing electrolyte secretion from mucosal cells
Infection is passed on through water contamination
Cholera symptoms start 2 - 3 days after ingestion of a large dose of bacteria
Symptoms include explosive watery diarrhoea + vomiting. Stool becomes colour + odourless. Water loss can be up to 1 litre per hour.
Main treatment continues to be large volumes of oral/intravenous rehydration.
Antibiotic treatment shortens disease + reduces severity. Doxycycline is commonly prescribed.
What is Clostridium perfringens?
What type of anaerobe is it?
When do symptoms occur?
What are the symptoms?
When does recovery happen?
Gram-positive endospore forming bacterium of the firmicutes
It is normal + non-invasive resident of the intestinal tract of humans + animals
3rd most common cause of reported bacterial food poisoning in the UK
Can cause gas gangrene when endospores infect wounds
C.perfringens is an obligate anaerobe (poisoned by oxygen) but when food is heated oxygen is driven off + heat resistant endospores form. Proliferation follows rapidly if cooling is too slow. If a large no. of bacteria is ingested, they produce toxins when they sporulate in the small intestine.
Symptoms occur 8 - 24 hrs after ingestion
Symptoms incyde abdominal pain, diarrhoea etc.
Resolve within 24 hrs
What is Staphylococcus aureus?
How many people are carriers + where is it found?
When do symptoms occur and what are they?
Gram-positive non-spore forming bacterium of the firmicutes
20% of people are carriers - found in moist folds of the human skin + upper respiratory infections
Infection of warm food followed by insufficient cooling leads to proliferation. Toxins are produced which are heat-resistant
Disease is caused by pre-formed toxin, onset is rapid, 1-6 hrs after ingestion.
Symptoms include nausea, vomiting + abdominal pain but without fever
Endospore forming bacterium can cause a very similar syndrome = Bacillus cereus (from reheated rice)
