Microbiology Path Flashcards
What is the definition of Diarrhoea?
Loose or watery stools at least 3x per day
What is the difference between small bowel and large bowel diarrhoea?
- Small bowel = large volumes and bloaty pain with fever, blood, mucus and inflammatory cells rare (secretory)
- Large bowel = smaller volumes and more severe abdominal pain with fever, blood, mucus and inflammatory cells more common (Secretory/Enteric)
Risk factors for Gastroenteritis?
Exposure related
- Contact with infected individuals (often shared environments)
- Travel (Where they went, where they stayed, what they did and what they ate/drank)
- Occupation including antibiotic use
- Animal contact (What animals and where?)
Host related
- Extremes of age
- Immunocompromised
- MSM (Anal)
Describe the presentation and Tx of E/Coli Gastroenteritis?
- Transmission = Faecally contaminated food/drink
- Incubation period = 1-3 days
- Presentation = Secretory diarrhoea lasting 2-3 days
Enterotoxic = Travellers
Enteropathogenic = infants
Haemorrhagic = Haemolytic Uraemic Syndrome
MENINGITIS IN CHILDREN - Tx = AVOID ANTIBIOTICS and give supportive care (fluids, electrolytes and nutritional support)
Describe the presentation and Tx of Vibrio Gastroenteritis?
- Transmission = Oral-faecal (particularly contaminated seafood for Parahaemolyticus)
- Incubation period = 1-3 days
- Presentation = Large volumes of diarrhoea lasting ~3 days. Cholerae = Watery (secretory) as the pathogen opens cAMP channels leading to Cl- efflux and with it water and electrolyte loss with little/no fever. Parahaemolyticus = Inflammatory with fever +/- mucus and blood
Tx = Doxycycline
Describe the presentation and Tx of Clostridium Gastroenteritis?
Transmission = - Contaminated food sources ( Canned/Vacumm foods and meat kept warm )
- Post-antibiotic use where gut flora gets diminished (difficile)
Incubation
- Short for Perfringens (8-16hrs) - - N/A for Difficile
Presentation
- Watery diarrhoea (secretory if perfringens)
+ Fever, mucus and blood if Difficile (inflammatory)
- Paralysis if Botulinum
Duration
- short (24-48hrs) if perfringens
- Prolonged (up to 10-14 days) if Difficile
Key points
- C.Dif toxins = A/B cause inflammation and damage to mucosa with B = more virulent
Tx
- Self-limiting and thus no Tx but supportive if Perfringens
- Oral Vancomycin if C.Dif
Describe the presentation and Tx of Campylobacter Jejuni?
Transmission
- Animal faeces
Incubation
- 1-3 days
Presentation
- Severe crampy abdominal pains with fever and foul-smelling diarrhoea +/- mucus/ blood
- Typically lasts 1-7 days
Extra-GI manefestations
- Haemolytic anaemia, HUS, Glomerulonephritis, Erythema Nodosum and Reactive Arthritis
Tx
- Normally self-limiting
- Eryhtromycin if immunocompromised
Describe the presentation and Tx of S.Aureus Gastroenteritis?
Transmission
- Preformed toxins on unrefrigerated foods
Presentation
- Very short incubation period (1-6hrs) with watery diarrhoea owing to the superantigen that binds MHC Class 2 and the TCR outside the antigen binding region to trigger cytokine release from CD4 +Ve cells
- Fever and vomiting owing to cytokine release
- Lasts 24-48hrs
Tx
- Self-limiting with supportive care
Describe the presentation and Tx of Shigella Gastroenteritis?
Transmission
- Faecal (raw vegetables and MSM)
Incubation
- 1-3 days
Presentation
- Abdominal pain
- 1/3 have watery diarrhoea, fever and vomiting
- 1/3 - 1/2 have bloody diarrhoea
Extra-GI manefestation
- Glomerulonephritis, HUS
Eryhtema Nodosum, Reactive Arthritis and Meningitis
Tx
- typically self limiting within 7 days so supportive only
Describe the presentation and Tx of Salmonella Gastroeneteritis?
Transmisison
- Non-typhoid = meat, unpasteurised dairy and eggs
- Typhoid = Humans
Incubation
- 1-3 days for non-typoid
- more insidious for typhoid
Presentation
- Non-typhoid = Inflammatory diarrhoea +/- vomiting
- Typhoid = Enteric fever (High fevers with possible constipation preceding diarrhoea)
Extra-GI
- Rose spots, splenomegaly and anaemia/leucopenia if Typhoid
- Erythema Nodosum, Reactive Arthritis, Aortitis, Osteomyelitis and Deep tissue inflammation also possible
Dx
- Stool antigen for non-typhoid
- Blood culture for Typhoid (hypernatraemia also seen)
Tx
- Non-Typhoid = self-limiting within 4-7 days
- Typhoid = Ceftriaxone
Describe the presentation and Tx of Listeria Monocytogenes Gastroenteritis?
Transmission
- Refrigerated foods (can replicate at 4 degrees celcius)
Incubation
- within a day
Presentation
- Inflammatory diarrhoea
- PARTICULARLY IMPORTANT IN PREGNANT WOMEN AS MOTHER MAY BE RELATIVELY OK BUT FOETUS MAY NOT
- Also seen in the immunocompromised
- Duration of illness variable
- MENINGITIS IN CHILDREN/INFANTS
Tx
- Amoxicillin
Describe the presentation and Tx of Yersinia Gastroenteritis?
Transmission
- Animals, typically pork
Incubation
- Long = 4-6 days
Presentation
- Inflammatory diarrhoea
- Abdominal pain
- May persist for 1-3 weeks
Extra-GI
- All except Meningitis and HUS
Describe Parasitic Gastroenteritis?
Transmission
- Oral-faecal ingestion of cysts containing trophozoites
- Once inside the body, the parasites excyst and attach to areas of the body to which they have a tropism ( Giardia = Duodenum, Cryptosporidium = Jejunum and Entamoeba = Liver (non-motile) or GI tract (motile))
Incubation
- Long = days to weeks
Presentation
- Flatus, bloating and diarrhoea in general
- Liver abscess = no diarrhoea, fever and RUQ pain if non-motile Entamoeba
- Severe = Cryptosporidium
Ix
- Stool
- Microscopy for Giardia = pear-shaped with 2 nuclei and 4 flagella or ELISA
- Iodine and Trichrome stains for Entamoeba
Tx
- Metronidazole for Giardia
- Metro + Paromomycin for Entamoeba
- Reconstitute immune system for Cryptosporidium
Describe Viral Gastroentritis?
Transmission
- Often Oral-Faecal
- Seafood suggests Norovirus
Incubation
- Short (10-16hrs for Enteric viruses)
- Longer for Norovirus = 24-48hrs
Presentation
- Watery diarrhoea
- Fever
- Vomiting suggests Norovirus
- URTI/Conjunctivitis suggests Adenovirus
Tx
- Supportive
What are the Extra-GI manifestations of Gastroenteritis and what are the associated organisms?
o Aortitis, Osteomyelitis and deep tissue inflammation = Salmonella and Yersinia
o Haemolytic anaemia = Campylobacter and Yersinia
o Glomerulonephritis = Campylobacter, Shigella and Yersinia
o HUS = E.Coli and Shigella
o Erythema Nodosum = Campylobacter, Shigella, Yersinia and Salmonella
o Reactive Arthritis = Campylobacter, Shigella, Yersinia, Salmonella and Giardia
o Meningitis = Shigella, E.Coli and Listeria Monocytogenes
Describe health promoting behaviours in respect to Gastroenteritis?
Targets for health promotion o Breast/Bottle feeding and food handling o Safe water o Waste disposal o Travel precautions o Isolation and PPE o PHE notification (Hx is very important) o GOOD HAND WASHING - Vaccinations
PHE notifiable GE pathogens o Campylobacter o Clostridium o Yersinia o Vibrio o Salmonella o Listeria Monocytogenes
