Flashcards in Microbiology Of Diarrhoeal Disease Deck (26):
What is the pathogenesis of bacterial pathogens?
Invasion and toxin release
Give examples of protozoal pathogen infections that cause diarrhoea.
What is the pathogenesis of a protozoal infection?
Invasion, followed by secretory products
Give examples of viral infection that can cause diarrhoea.
Norovirus, astrovirus and rotavirus
Also, HIV when associated with long infection and carriage of other pathogens
What is the pathogenesis of a viral infection?
Local invasion, cytopl this effect and lastly cell destruction
Name some of the host factors that would make them more susceptible to infection
Species, genotype, age, personal hygiene, gastric acidity and other physical barriers, intestinal motility, enteric microflora, immunity, non-specific protective factors in human milk, intestinal receptors and iatrogenic factors
What microbial factors affect how infectious they are?
Toxins, attachment, invasiveness, infectious dose. And other virulence factors
What is the infectious dose of shigella?
10 to 100 organisms
What is the infectious dose of campylobacter jejuni?
100 to 1,000,000 organisms
What is the infectious dose of salmonella?
What is the infectious dose of vibrio cholerae?
What is the infectious dose of giardia lamblia?
10 - 100 cysts
What are the three groups of enteric bacterial toxins?
Secretory enterotoxin group
Name some of the bacteria from the neurotoxin group.
Staphylococcus aureus (enterotoxin b)
Bacillus cereus (emetic toxin)
Name some of the bacteria from the secretory enterotoxin group.
Vibrio cholerae (cAMP)
E.coli LT, STa and STb
Name some of the bacteria in the cytotoxic group.
What are the three main mechanisms of enteric infection by bacteria?
Noninflammatory (enterotoxin or adherence)
Inflammatory (invasion, cytotoxin)
Give an example of illnesses caused by noninflammatory, inflammatory and penetrating infections.
- proximal small bowel problems causing watery diarrhoea
- problems in the colon, causing dysentery
- enteric fever found in the distal small bowel
What would be found in the stool in noninflammatory, inflammatory and penetrating infections?
- no fecal leukocytes, and a mild (or no) rise in lactoferrin
- presence of polymorphonuclear leukocytes and a large increase in lactoferrin
- presence of feacal mononuclear leukocytes
Give some examples of bacteria that cause noninflammatory infections.
E.coli, EHEC, LT, ST
Give some examples of bacteria that cause inflammatory infections.
E.coli (EIEC, EHEC)
Give some examples of bacteria that cause penetrative infections.
Name some of the tests that are used in organism identification.
Selective culture media
Differential culture media
Macroscopic and microscopic appearance
Staining - gram, auramine
Serology - e.g. Salmonella
Biochemical gets - single tests, APIs, fermentation reactions
Cell culture and cytopathic effects
Rapid tests - LDH, rotavirus
Reference and lab testing - non-molecular and molecular
What history would you ask of someone with severe diarrhoea?
Fever, Blood, Seafood, Antibiotic use, Weight loss, Travel, Outbreak, Sexual experience, Abdominal pain, Immunosupression and you must also obtain a stool for WBCs and parasites
Give the five main mechanisms of treatment for bacterial diarrhoea.
Conservative - rehydration and nutrient
Antibiotics - enteric fever, vaccine for C.diff
Surgery - for fulminant colitis (C.diff)
Infection control - single room or cohort isolation, hand hygiene
Public health - outbreak surveillance, exclusions and microbiological clearance