GI Infections Flashcards
What symptoms characterise gastroenteritis?
Nausea
Vomiting
Diarrhoea
Abdominal. discomfort
Define diarrhoea
Frequent and/or fluid stool, at least 3 episodes a day
What is dysentery?
The presence of blood and pus in the stools usually accompanied with abdominal pain and fever
What is endocolitis?
Inflammation involving the mucosa of the small and large intestines
Which groups of people are at higher risk of viral gastroenteritis?
Children under five
Elderly people (especially those in nursing homes)
Immunocompromised patients
Give five examples of important viruses which cause gastroenteritis
Norovirus Rotavirus Adenovirus (40 and 41) Astrovirus Sapovirus
Which viruses most commonly affects children under two, elderly people and immunocompromised people to cause gastroenteritis?
Rotavirus
Adenovrius
Astrovirus
Most viruses can’t be cultures. How then, are viruses which cause gastroenteritis detected?
PCR
Describe the structure of norovirus?
Non-enveloped
Single stranded RNA
How can norovirus be transmitted?
Direct person-person transmisssion via faecal-oral route or aerosolised droplets
Food/water borne transmission
Norovirus has a high infectious dose. T/F?
False- the infectious dose of norovirus is low (10-100 viridons)
What is the incubation period of norovirus?
24-48 hours
Norovirus can shed for up to how many weeks post-infection?
3 weeks
What are the clinical features of norovirus?
Vomiting Diarrhoea Nausea Abdominal cramps Headache Muscle aches Fever Dehydration
How long do the symptoms of norovirus last for?
12-60 hours
For how long post-infection can norovirus shed for in solid organ/bone marrow transplant patients?
2 years
How is norovirus infection treated?
Oral/IV fluids
Antispasmodics
Analgesics
Antipyretics
Antibodies are developed to norovirus but these only remain for a short period, provide no long-lasting immunity. T/F?
True
What are the infection control policies for norovirus infection?
Isolation and cohosting of patients
Symptomatic staff excluded until symptom free for 48 hours
Patients should not be moved
New patients should not be admitted
Describe the structure of rotavirus?
Non enveloped
Double stranded RNA virus
Rotavirus has a low infectious dose and is stable in the environment. T/F?
True
What is the incubation period of rotavirus?
1-3 days
How is rotavirus transmitted?
Mainly by the faecal-oral route or fomites
Food/water borne spread possible
What are the symptoms of rotavirus infection?
Watery diarrhoea
Abdominal pain
Vomiting
Loss of electrolytes leading to dehydration
For how long do the symptoms of rotavirus infection normally last?
3-7 days
What are the possible complications of rotavirus infection?
Severe chronic diarrhoea
Dehydration
Electrolyte imbalance
Metabolic acidosis
Antibodies against rotavirus are produced and this leads to immunity against further infection. T/F?
False - the antibodies which are produced don’t lead to permanent immunity but do lessen the severity of subsequent infection
A rotavirus vaccine is available. T/F?
True
Describe the structure of adenovirus?
Double stranded DNA virus
Which serotypes of adenovirus cause gastroenteritis?
Adenovirus 40 and 41
What are the symptoms fo adenovirus 40/41 infection?
Fever
Watery diarrhoea
Describe the structure fo astrovirus
Single stranded RNA virus
Non-enveloped
Astrovirus causes very severe gastroenteritis compared to other aetiologies. T/F?
False - astrovirus causes less severe gastroenteritis than other enteric pathogens
In the developed world, what mode of transmission is mainly associated with GI infection?
Food-borne infection
In the developing world, what is the biggest factor contributing to GI infection?
Lack fo clean water and poor sanitation
Give examples of the physiological barriers to infection of the GI tract.
Lysoyme in the mouth
Acidic pH of the stomach
Mucous/bile/secretory IgA/ lymphoid tissue/epithelial turnover/normal flora of the small intestine
Epithelial turnover/normal flora of the large intestine
The normal flora of the small and large intestines are mostly what type of microorganisms?
Anaerobes
Many GI infections are zoonotic. What does this mean?
They are transmitted to humans from animals
What key factors are important to establish when taking a history from a patient with GI infection?
Nature of diarrhoea Timing (acute/chronic) Food history Recent antibiotic usage Foreign travel Occupation
What investigations should be conducted for a patient with GI infection?
FBC U&Es Blood film Stool sample Sigmoidscopy Abdominal X-RAY/CT
What is an enrichment broth?
Contains nutrients that promote the preferential growth of the pathogen
What is selective culture media?
Suppresses the growth of background flora while allowing the growth of the pathogen
What is differential culture media?
Distinguishes mixed microorganisms on the same plate using biochemical characteristics of microorganisms growing in the presence of specific nutrients combined with an indicator which changes colour
What is the most important factor in the treatment of GI infection?
Hydration / giving the patient fluids
Why is antibiotic treatment generally not used for GI infection?
May prolong symptom duration
Exacerbate symptoms
Promote emergence of antibiotic resistance
Be harmful such as in STEC infection
How can GI infections be prevented?
Provision of safe, clean drinking water Proper sewage d isposal Education in hygienic food preparation Pasteurisation of milk and dairy products Sensible travel food practices
Describe why there is such as potential for new enteric pathogens to emerge?
Pathogenecity traits are often grouped together in large interns of pathogenicity. These can be transferred to other organisms via bacteriophages, plasmids and transposons.
Pathogenicity traits frequently contain antibiotic resistance genes
Why do GI infections caused by intoxication have a short incubation time?
Because the preformed toxin is present in food and usually takes only a few hours for symptoms to appear.
What are three of the most common causes of GI infection?
Salmonella
Campylobacter
E.coli
What type of bacteria is salmonella?
Gram negative bacilli
Salmonella are non-lactose fermenters. T/F?
True
How can salmonella infection be acquired?
Contaminated food especially pork, poultry and other meat and dairy products
Waterborne infection is less common
There are seasonal peaks of salmonella infection in which months?
Summer and autumn
How does salmonella cause diarrhoea?
By invading epithelial cells in the distal small intestine, causing inflammation
What are the possible results of metastatic salmonella infection?
Osteomyelitis
Septic arthritis
Meningitis
What is the incubation period of salmonella?
12-72 hours
What are the symptoms of salmonella infection?
Watery diarrhoea
Fever
Vomiting
In severe salmonella infections, what antibiotics may eb used?
Beta lactams
Quinolones
Aminoglycosides
What type of bacteria are campylobacter?
Gram negative bacilli
What is the most clinically important species of campylobacter?
C.jejuni
What animals can acts as a reservoir for campylobacter?
Poultry Cattle Sheep Rodents Wild birds
In what months is there seasonal peaks of campylobacter infection?
May
September
How is campylobacter transmitted?
Contaminated food, milk and water
How does campylobacter infection cause diarrhoea?
Causes inflammation, ulceration and bleeding in the small and large intestines via bacterial invasion
In rare cases campylobacter infection can cause post-infectious demyelinated syndrome. T/F?
True
What is the incubation period of campylobacter?
2-5 days
How long do the symptoms fo campylobacter infection last?
2-10 days
What are the symptoms fo campylobacter?
Bloody diarrhoea
Cramping abdominal pain
Fever
(Vomiting not usually a feature)
Which antibiotics can be used to treat severe or persistent campylobacter infection?
Clarithromycin
Erythromycin
What type of bacteria is e.coli?
Gram negative bacilli
What are the six diarrhoeagenic groups of E.coli?
Enteropathogenic E.coli Enterotoxigenic. e.coli enterohaemorrhagic e.coli enteroinvasive e.coli entero-agrgegative e.coli diffuse aggregative e.coli
What syndrome may result form the use fo antibiotics in e.coli infection?
Haemolytic uraemic syndrome
What are the symptoms of enteropathogenic e.coli infection?
Watery diarrhoea
Abdominal pain
Vomiting
Fever
Describe the pathophysiology fo enteropathogenic e.coli infection?
Adheres via pili, forms attaching and effacing. lesion which is mediated by intimin protein
Disrupts intestinal microvilli
What is the major bacterial cause fo diarrhoea in infants and children in the developing world?
Enterotoxigenic e.coli
What are the symptoms of enterotoxigenic e.coli infection?
Watery diarrhoea
Abdominal pain
Vomitng
No associated fever
What is the incubation period of enterotoxigenic e.coli?
1-7 days
How long do the symptoms fo enterotoxigenic e.coli infection last for?
2-6 days
How does enterotoxigenic e.coli cause diarrhoea?
Heat labile and heat stabile toxins which are structural and functional analogues of the cholera toxin
What is the most common serotype of enterohaemorrhagic e.coli?
E.coli 0157
What is the main mode of transmission of enterohaemorrhagic e.coli?
Contaminated food, water and dairy products
Direct environmental contact with animal faeces
What toxins are produced by enterohaemorrhagic e.coli?
Shiga like toxins
What is the incubation period of enterohaemorrhagic e.coli?
1-7 days
How long do the symptoms fo enterohaemorrhagic e.coli infection last for?
5-10 days
What are the symptoms of enterohaemorrhagic e.coli infection?
Bloody diarrhoea
Abdominal pain
Vomiting
No associated fever
What is haemolytic uraemiac syndrome?
A triad of microangiopathic haemolytic anaemia, thrombocytopenia and acute renal failure
What type of bacteria is shigella?
Gram negative bacilli
What are the four species fo shigella?
Shigella sonnei
Shigella boydii
Shigella flexneri
Shigella dysenteriae
Which. species of shigella is associated with milder infections?
Shigella sonnei
Which species of shigella is associated with the most severe disease?
Shigella dysenteriae
Shigella does not persist in the environment. Thus, what is the most important mode of transmission of shigella?
Person to person spread via the faecal-oral route
S.dysenteriae produces a potent protein exotoxin (shiga toxin) which damages the intestinal epithelium. What other structures can this target?
Glomerular epithelium causing renal failure
Infection with which organism is the most common cause of dysentery?
Shigella
What are the symptoms fo shigella infection?
Marked, cramping abdominal pain
Dysentery
Fever
Vomiting is uncommon
What type of bacteria is vibrio cholerae?
Gram negative bacilli
In what parts of the world is vibrio cholerae endemic?
Southeast Asia
Africa
South America
Vibrio cholerae has many. animal reservoirs. T/F?
False - it only infects humans
How does vibrio cholerae spread?
Contaminated food and water
What are the symptoms fo vibrio cholerae infection?
Sever, profuse water diarrhoea
Profound fluid loss and dehydration causing hypokaelamia, metabolic acidosis, hypovolaemic shock, cardiac failure
What type fo antibiotics may shorten the duration of shedding of vibrio cholerae?
Tetracyclines
S.aurerus toxins causing Gi infection are especially present in which foodstuffs?
Meats
Cakes
Pastries
What are the symptoms of s.auerus toxin mediated GI infection?
Profuse vomiting
Abdominal cramps
No fever or diarrhoea
What is the incubation time for s.auerus toxin mediated GI infection?
30 minutes
What type of bacteria are bacillus cereus?
Gram positive bacilli
What foodstuffs are typically associated with b.cereus GI infection?
Fried rice
What are the symptoms of b.cereus toxin mediated emetic GI infection?
Profuse vomiting
Abdominal cramps
Watery diarrhoea
No fever
What is the incubation period of b.cereus toxin mediated emetic GI infection?
30mins-6hours
What are the symptoms of b.cereus toxin mediated diarrhoea GI infection?
Watery diarrhoea
Cramping abdominal pain
No vomiting or fever
What is the incubation period of b.cereus toxin mediated diarrhoeal GI infection?
8-12 hours
What type of bacteria is clostridium perfringens?
Anaerobic gram positive bacilli
What are the symptoms of c.perfringens toxin mediated GI infection?
Watery diarrhoea
Abdominal cramps
No fever or vomiting
What is the incubation period of c.perfringens toxin mediated GI infection?
6-24hours
Which heat-labile protein neurotoxins of clostridium botulinum cause disease in humans?
Types A, B and E
What foodstuffs is preformed botulism toxin particularly associated with?
Improperly processed canned foodstuffs
What are the symptoms fo clostridium botulinum toxin mediated disease?
Flaccid paralysis
Progressive muscle weakness
Respiratory failure of chest/diaphragm involved
What is used to treat clostridium botulinum toxin mediated disease?
Antitoxin
Other than antibiotics, which drugs are associated with c.difficile infection?
Proton pump inhibitors
What condition may result from severe c.difficile infection?
Pseudomembranous colitis
In mild c.difficile infection what antibiotic is given?
Oral metronidazole
In severe c.difficile infection what antibiotic is given?
Oral vancomycin
What type of bacteria is listeria monocytogenes?
Gram positive coccobacili
What groups of people are more likely to become infected with listeria monocytogenes?
Pregnant women
Elderly people
Immunocompromised individuals
Which foodstuffs are particularly associated with listeria monocytogenes?
Unpasteurised milk Soft cheese pate Cooked meats Smoked fish Coleslaw
What can result from severe, systemic infection with listeria monocytogenes?
Septicaemia
Meningitis
Which antibiotics are used to treat listeria monocytogenes infection?
IV Ampicillin and gentamicin
What is the incubation period of listeria monocytogenes?
3 weeks
For how long does listeria monocytogenes infection cause symptoms?
1-2 weeks
