Microbiology Of Diarrhoeal Disease Flashcards
What is the pathogenesis of bacterial pathogens?
Invasion and toxin release
Give examples of protozoal pathogen infections that cause diarrhoea.
Cryptosporidium, giardia
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?
100,00 organisms
What is the infectious dose of vibrio cholerae?
100,000,000 organisms
What is the infectious dose of giardia lamblia?
10 - 100 cysts
What are the three groups of enteric bacterial toxins?
Neurotoxin group
Secretory enterotoxin group
Cytotoxic group
Name some of the bacteria from the neurotoxin group.
Clostridium botulinum Staphylococcus aureus (enterotoxin b) Bacillus cereus (emetic toxin)
Name some of the bacteria from the secretory enterotoxin group.
Vibrio cholerae (cAMP) Nonchloerae vibrios E.coli LT, STa and STb Salmonella Klebsiella Clostridium perfringens Shigella dysentery B.cerus
Name some of the bacteria in the cytotoxic group.
Shigella S.aureus Vibrio paraheamolyticus Clostridium difficile E.coli, EHEC Campylobacter jejuni H.Pylori Bacteriodies fragilis
What are the three main mechanisms of enteric infection by bacteria?
Noninflammatory (enterotoxin or adherence)
Inflammatory (invasion, cytotoxin)
Penetrating
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.
Vibrio cholerae E.coli, EHEC, LT, ST Clostridium perfringens Bacillus cereus Staphylococcus aureus
Give some examples of bacteria that cause inflammatory infections.
Shigella E.coli (EIEC, EHEC) Salmonella Vibrio paraheamolyticus Clostridium difficile Campylobacter jejuni
Give some examples of bacteria that cause penetrative infections.
Salmonella
Yersinia
Enterocolitica
Campylobacter fetus
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 Agglutination tests 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
Give examples of bacterial pathogens that cause diarrhoea.
Salmonella, shigella, E.coli, campylobacter, bacillus
