L9 - GI Infections 1 : Bacterial Gastroenteritis Flashcards
Describe norovirus
- incubation periods
- symptoms
- diagnosis
Incubation period: 24-48hrs
Prominent vomitting.
Diagnosis
- electron microscopy, antigen or DNA detection (PCR) in stool
Astrovirus
- symptoms
Symptoms
- diarrhoea in small children and immuno-compromised individuals
Rotavirus
- incubation period
- symptoms
- where does it infect
Infects enterocytes, major cause of diarrhoea in kids.
48hr incubation period.
Watery diarrhoea, vomitting, fever, abdominal pain and dehydration.
Diagnosis: enzyme immunoassay
Cholera
- organism
Vibrio cholerae - comma shaped, gram negative.
Contaminated drinking water
Pathogenesis of cholera and how it will eventually cause diarrhoea
Cholera - 5 beta subunit, 1 alpha subunit
- 5 beta subunit binds to GM1 ganglioside on surface of interstitial cell
- Enters via endocytosis , retrorgrade transport
- RER: ASU reduced by disulfide isomerase
- ASU fragment unfolded and released into cytosol
- Transported via host cell machinery. Normally hcm would move and sipose of misfolded proteins via proteasome.
- ASU refolds to avoid degradation
- ASU interacts with cytosolic ADP ribosylation factors to ribosylate and activate stimulatory G-proteins
- adenyl cyclase
- increases intracellular cAMP
- cAMP inhibits Cl-, Na+ absorption
- Opens CFTR channels
- Release Cl-
- Cl-, Na+, HCO3- accumulate in lumen, cause osmotic pull of water into lumen
- DIARRHOEA
Clinical features of cholera
Voluminous stools. Fishy odour. Dehydration. Hypotension. Muscular cramping. Anuria. Shock.
What might be given to relieve symptoms of cholera
CFTR inhibitor blocking Cl- secretion.
Prevents diarrhoea
Describe campylobacter entercolitis?
Food poisoning.
Motility, adherence, toxin production and invasion.
Describe shigella
Gram negative, Bloody diarrhoea. Causes Shigellosis.
Resistant to acidic pH of stomach.
Travels to intestine and is taken up by M-cells.
Shigella proliferate and escape into laminar propia.
Phagocytosis by macrophages.
Induce apoptosis
- inflammatory response
What are M cells
Intestinal epithelial cells specialised for antigen sampling.
Salmonella
Salmonella typhi causes typhoid fever.
Non typhoid salmonella.
Capable of transferring bacterial proteins into M-cells
Ribosylation
Addition of ribose to a protein
ADP
Describe typhoid fever?
Salmonella enterica.
Able to survive in gastric acid.
Taken up by M-cells once in small intestine.
Bacteria engulfed by mononuclear cells in the underlying lymphoid tissue.
symptoms:
- anorexia
- abdominal pain
- bloating
Describe the different toxins that E-Coli produce?
Heat labile toxins LT
Heat stable toxins ST
Both induce chloride and water secretion while inhibiting intestinal fluid absorption
Describe the LT toxin produced by E-coli
Activates adenylate cyclase.
Increases cAMP.
Stimulates Cl- secretion.
Simultaneously inhibits absorption.
Describe the ST toxin produced by E-coli
Binds to guanylate cyclase.
increases cGMP
Describe psuedomembrane colitis?
- Generally caused by C-Diff
- toxins cause ribosylation of small GTPases, RHO family of GTPases
- leads to disruption of epithelial cytoskeleton, tight junction barrier loss, cytokine release and apoptosis.
Norovirus will cause..
Norovirus: single stranded, RNA genome
Mild villous shortening.
Loss of microvilli brush border.
Crypt hypertrophy.
Lamina propia infiltration by lymphocytes.
Describe damage caused by rotavirus
Rotavirus: segmented double stranded RNA genome.
Enterocyte damage can induce epithelial apoptosis.
Antibodies in breast milk provide protection.
Damage caused by adenoviruses
Non-specific villous atrophy.
Compensatory crypt hyperplasia.
Summarise the three main ways that bacteria can cause diarrhoea?
- Secretory toxins
- Cytotoxins
- Direct invasion
- tends to be intracellular bugs
Presentation of Campylobacter jejuni
Abdo pain
Diarrhoea +/- dysentry
Complications of campylobacter jejuni
Guillain-Barre syndrome
- ascending weakness and sensory loss starting in toes to fingers.
Reactive arthritis
- joint pain and swelling triggered by an infection in another part of the body
Presentation of salmonella spp. (non-typhoidal)
Diarrhoea
Vomiting
Fever
Complications of salmonella spp. (non-typhoidal)
Bacteraemia +/- metastatic infection Septic arthritis (sickle cell)
Incubation period of Campylobacter jejuni
Days
Incubation period of Salmonella spp. (non typhoidal)
Hours - Days
Presentation of Shigella spp.
Diarrhoea +/- dysentery
Complications of Shigella
Haemolytic-uraemic syndrome (VTEC)
- destruction of blood platelets (clotthing)
- low red blood cell count (anaemia)
- kidney failure due to damage of very small blood vessels of the kidneys
Incubation of Shigella
Days
Source of Shigella
Human GI tract
Source of E-Coli
Human GI tract
Incubation of E-coli
Hours to days
Presentation of E-coli infection
Traveller’s diarrhoea
UK diarrhoea outbreaks
Complications of E-coli
Haemolytic-uraemic syndrome
Reservoir of Bacillus cereus
Found in food / environment
Incubation of Bacillus cereus
Hours
Presentation of Bacillus cereus
Diarrhoea (enterotoxin-producing strain)
Vomiting (emetic toxin-producing strain)
Reservoir of Staph aureus
Human skin
Nasopharynx
Incubation of S.aureus
Hours
Presentation of staph aureus
Abdo pain
vomiting
not usually associated with diarrhoea
Reservoir of clostridium perfringens
Animals / environment
Incubation of Clostridium perfringens
hours
Presentation of clostridium perfringens
abdo pain
diarrhoea
Complications of clostridium perfringens
Enteritis necroticans (group c) - segmental necrotizing infection of jejunum and ileum
Reservoir of Yersinia enterocolitica
Animals (mainly pigs)
Incubation of Yersinia enterocolitica
days
Presentation of Yersinia entercolitica
Abdo pain
Diarrahoea
Fever
Appendicitis mimic in children
Reservoir of vibrio cholerae
Water
Incubation of vibrio cholerae
Days
Presentation of vibrio cholerae
Profuse ‘rice water’ diarrhoea
Source of listeria monocytogenes
animals, environment
Incubation of listeria monocytogenes
days - months
Presentation of Listeria monocytogenes
Diarrhoea, fever
Complications of listeria monocytogenes
Bacteraemia
Meningitis
Septic abortion
Guarding
Tensing up when you touch a particular area e.g. patients hand
Why is it important to wash hands with soap and water and not just alcohol?
Clostridium perfringens is a gram positive bacterium producing spores.
These spores are not killed by alcohol.
Case study
28 y/o sales assistant.
Progressive ascending weakness and sensory loss in hands and feet.
1 month ago, had episode of bloody diarrhoea and abdominal pain 2 days following barbecue
Campylobacter (bbq bug)
Ascending weakness: indicative of Guillain Barre syndrome
No mention of vomiting, vomiting unusual for C.bacter
Blood in diarrhoea
Case study
45 y/o , vomiting, diarrhoea and fever. Returned from spain 24hrs ago. Had egg salad sandwich at airport
Travel history: Salmonella
Eggs abroad might not meet safety standards set by UK.
Case study
31 y/o nursery assistant. 2 day history of bloody diarrhoea.
Shigella
Haemolytic-uraemic syndrome
- massive activation of clotting platelet aggregation factor.
- bleeding damage to kidneys
Case study
6/o fever, nosebleeds, severe hypotension. Platelet count low, prothrombin time up, creatinine very high. 1 week ago she had an episode of diarrhoea and vomiting following visit to petting zoo.
Severe acute kidney injury.
Caused by E-coli
Associated with cows and goats.
Case study
19 y/o , severe vomiting and abdominal pain 4hrs after eating egg fried rice from local take away
Bugs associated with reheated rice - Bacillus Cereus
Extremely severe vomiting.
Even though bacillus might be dead the heat stable toxin left in rice.
Case study
24 y/o presents with vomiting 45 mins after eating pre-prepared sandwiches at conference. Illness resolves within 24hrs
Staph aureus
- not usually associated with diarrhoea
Case study
45 y/o nurse, abdominal pain and diarrhoea 24hrs after eating at buffet
Clostridrium perfringens
Tends to be associated with food that hasnt been kept warm properlly
Case study
24 y/o sever abdo pain and diarrhoea. Undergoes a laparotomy and her appendix is removed
Yersinia entercolitica
- severe abdominal pain
Case study
31 y/o health care worker providing hurricane relief has severe mucoid diarrhoea and is visibly dehydrated and hypotensive
Vibrio cholerae
profuse ‘rice water’ diarrhoea
contamination of water supply
Case study
29 y/o pregnant woman presenting with diarrhoea, fever and confusion after recent trip to France
Unpasteurised cheese.
Listeria associated with meningitis , tropism for CNS tissue.
Can replicate at very low temperatures.
