Simon Swift Flashcards
How does Clostridium difficile cause disease?
After antibiotics it can survive and repopulate without competition or it forms endospores that then repopulate after the chemotherapy has been stopped.
What kills endospores?
Autoclaving, chemicals.
Resistant to heat and antibiotics
What are the toxins of clostridium difficele and how does it cause disease?
Toxin A and Toxin B.
Attach to the surface of the clonic mucosa, are taken into a vesicle, pH is reduced and the toxins are activated. The toxin is then released into the cytoplasm. Reduces the actin cytoskeleton.
This causes a loss of barrier in the intestine mucosa. Toxins get into the submucosa and cause inflammation. Less water absorption causes diarrhea.
A pseudo membrane forms in the inner layer of the intestine causing ulceration.
How do you identify a clostridium difficele infection?
Look for the toxin. Most patients have the bacteria but the toxin indicates causation.
Take stool sample. Binds to antibody in a test.
Can do a PCR for the toxin.
How do you treat clostridium difficle infection?
Discontinue implicated antibiotics.
Treat with metronidazole or oral vancomyocin.
Treat fluid loss and pain.
Replace fecal flora. Fecal transplant.
What sort of bacteria is metronidazole good to treat?
Anaerobic bacteria
What sort of bacteria is clostridium difficle?
Gram positive obligate anaerobe
What are the signs and symptoms of acute GI illness?
Vomiting, diarrhea, fever, abdominal pain
What are the causes of GI illness?
Virus - fast onset (days to hours), vomiting, fever, probably diarrhoea.
Bacteria: onset varies, diarrhoea, probably vomiting, abdominal pain, sometimes needs antibiotics.
Protozoa: slow onset (days/weeks), diarrhoea, possibly vomiting, abdominal pain, probably need antibiotics.
All need rehydration.
What are specific examples and pathogenesis of viral causes of GI illness?
Norovirus or rotovirus.
Small intestine
Caught through vomit or diarrhoea that is infected.
Nausea and vomiting Watery diarrhoea Abdominal cramps Fever headache
Self-limiting over 48 hours.
What are specific examples of bacterial causes of GI illness?
Colonisation of intestines and the production of toxins Clostridium difficle Shiga toxin producing E. Coli Vibro cholerae Enterotoxigenic E. Coli
Colonisation then invasion of intestinal tissue causing inflammation:
Campylobacter jejuni
Non-typhoid salmonella
Enteroinvasive E. Coli
Toxin in food but no bacteria (food poisoning)
S Aureus
Found in foods or toxins found in foods. Also water.
Colonization and production of toxins. Causes inflammation -> diarrhoea.
What are specific examples of protozoa causes of GI illness?
Colonisation of the small intestine.
Giardia lamblia
Cryptosporidium
Food/water contamination with human/animal faeces
Incubates for 1+ weeks
Diarrhoea, cramps
May need antibiotics (metronidazole)
What is the definition of an outbreak?
2 or more causes linked to a common source.
What are the routs of transmission of GI illnesses and what are ways to reduce the spread?
Faecal/oral route - direct or indirect.
Animal faeces -> contaminated meat -> eat food -> AGI
Animal faeces -> contaminates fertilized veges -> eat -> AGI
Person with AGI -> poop on food item -> someone eats -> AGGI
Direct consumption of poop -> AGI
Animal/human faeces -> contaminate water -> drink water -> AGI
Animal/human faeces -> contaminate water -> irrigation -> eat food -> AGI
- Clear slaughter
- test for contamination
- good farming practice.
- Appropriate food storage
- Cook well
- Good hygiene
- Effective sourage systems.
What are the risk factors for AGI?
Being around a symptomatic person. Being near animals Eating from a restraunt. Eating at risk food products. Drinking untreated water. Contact with poop Contact with recreational water Overseas travel
How do you determine the pathogen for AGI?
Stool culture.
If clostridium defficele or Shiga toxin producing E. Coli is suspected then need fast diagnosis:
Toxin tests - antibody and PCR
If there is an outbreak it suggests a virus. Do PCR or antibody test on the stool.
If 4+ weeks of diarrhoea then it’s not bacterial - giardia lamblia or cryptosporidium - antigen test
What are the complications of AGI?
Dehydration
Bacteraemia
How do you treat AGI?
Rehydration - need access to clean water, sugars and salts.
Easily digestible foods.
Antibiotics - usually not required - may be good to reduce transmission.
How do you prevent AGI?
Sanitation - clean water and swerage Hygine Effective cooking Food regulations avoid risky food and drinking water.
What are the common causes for bloody diarrhoea?
Shigella
Shiga toxin E. Coli
What bacteria ferment sorbital on MacConkey plates?
Most E. Coli but not shiga toxin producing E. Coli
What bacteria ferment lactose on MacConkey plates?
E. Coli
Salmonella, shigella do not.
What grows on XLD plates?
Salmonella and shigella
Salmonella forms black spots and shigella white spots
Most other gut bacteria form yellow.
Why would you not give antibiotics to treat shiga toxin producing E. Cloi?
Because it can increase toxin production, shown in vitro.
What pathogens would you treat for AGI?
Clostridium difficile (vancomyocin, metronidazole) Salmonella/camplyobacter if at risk of systemic infection
What bacteria are at risk of causing a systemic infection in AGI?
Salmonella and campylobacter - if at risk, treat with antibiotics
What are the potential complications with shiga toxin producing E. Coli?
Haemolytic uremic syndrome - effects kidneys
When would you want to give anti-motility drugs?
For acute watery diarrhoea..
Shigella dysenteriae and shiga toxin producing E. coli, vibrio choleria
Virus
When would you want to give treatment for cholera?
To reduce outbreaks
What are the symptoms of peritonitis?
Fever Increased heart rate Increased RR Nausea and vomiting Diffuse abdominal pain
Rebound tenderness
Abdominal wall rigidity
Increased blood leukocytes
CT/US: fluid accumulation
Loss of bowel sounds/movement
What is peritonitis?
Inflammation of the peritoneum
Spontaneous - rare -
Secondary - common. Loss of GI tract integrity or from infected viscera.
What is the pathogen of peritinitis?
Usually polymicrobial
- synergistic infections
Enterobacter, E. coli
Bacteroides fragilis (anerobe)
Enterococci
What are the main routes of transmission of from the GI tract to the peritoneium?
Appendicitis (ruptured) Diverticulitis (rupture) Stomach/duodenal ulcer Pelvic inflammatory disease Surgery
What happens in the peritoneum?
Clearance not effective in the clearance of nutrients. If too many bacteria, innate immune cells can’t clear the bacteria.
Results in inflammation - fluid accumulation in peritoeneal cavity, which can dilute the antibacterial factors and may lead to hypovolemia
Bacteria can get contained in an abscess by the deposition of fibrin. Bacteroides fragilis promotes firbirin deposition
The bacteria touch the side of the cavity and fibrin is deposited
How do you diagnose?
Take away any pus for culture
Grams stain
Do both aerobic and anerobic cultures
What plate do you culture an anerobe on?
Bile aesculin agar
What is another way to identify bacteria?
Mass spectrometry
What are the features of bacteroides fragilis?
Synergistic function with E. Coli. Needs iron and E. coli acquires iron
Capsule - prevents phagocyosis LPS Capsules indices fibrin deposition Complement degredation by proteases Reduced oxygen toxicity
How do you treat peritonitis?
Pain relief, fluids, removal of pus
Establish cause of infection and specific species
Corrective surgery to repair cause
Antibiotic needs to be broad spectrum because of polymicrobial.
Trippe antibody treatment:
Aminoglycoside to treat the E.coli
Metonidazole to treat the anaerobes (bacteroides flagilis)
Ampicillin to treat the enterococcus
What is metronidazole good to treat?
Anaerobic bacteria
Aerobic protozoa
Giardia lamblia, trichomonas, bacteroidies
Clostridium dificele
Stops DNA synthesis
