microbial foodborne infections and intoxications part 1 W4 Flashcards
definition of gastro-enteritis?
inflammation of the digestive tract (causing nausea, vomiting, abdominal pain, diarrhoea, eventually fever)
causes of gastro-enteritis? what are their different effects?
viral (most common) - stomach flu
parasite
bacterial - microbial food poisoning
examples of viral causes of gastro-enteritis?
norovirus
rotavirus
adenovirus
types of bacterial causes of gastro-enteritis?
infection = viable microorganisms
intoxication = only toxin
examples of infection bacterial causes of gastro-enteritis?
campylobacter spp
salmonella spp
e. coli
examples of intoxication bacterial causes of gastro-enteritis?
clostridium perfringens
bacillus cereus
staphylococcus aureus
clostridium botulinum
e. coli
ways to distinguish mechanisms of microbial infections
is food a vector or does the microorganism need it to grow?
does the microorganism have to replicate in the host to cause symptoms? (eg not the case in intoxication, some infection)
is ingestion of pre-formed toxin sufficient to cause symptoms?
mild gastro-enteritis clinical description?
self-limiting (usually)
2-3 days
3 or less stools/day
low/no fever
general condition = satisfactory
moderate gastro-enteritis clinical description?
> 3days
3-5 stools/day
T<38°C
general condition = moderate
serious gastro-enteritis clinical description?
invasive diarrhoea
> 3 days
≥ 5 stools/day
T>38°C
bloody diarrhoea
(dysentery, colitis)
general condition = bad
small bowel infection features
role = fluid secretion/nutrient absorption
watery diarrhoea
abdominal cramping
bloating
gas
large bowel infection features
role = absorb fluid and salt
watery or bloody/mucoid diarrhoea
low abdominal pain
fever++
differential diagnosis: watery diarrhoea, no fever?
Cholera
differential diagnosis: watery diarrhoea, fever?
norovirus
rotavirus
ETEC
bacillus cereus
staphylococcus aureus
differential diagnosis: bloody diarrhoea, no fever
(rare, mainly parasitic causes)
entamoeba histolytica
campylobacter
salmonella
differential diagnosis: bloody diarrhoea, fever?
shigella
campylobacter
non-typhi salmonella
C perfringens
EIEC/EHEC
what is infective dose?
the number of pathogens needed to cause disease in the new host
varies with the pathogen, relatively high for all bacteria
general infective dose for viruses/parasites/bacteria?
viruses low, parasites medium, bacteria high
campylobacter species:
where does it act?
infective/intoxication?
features?
diarrhoea/fever?
infective, acts on small and large bowel
microaerophilic, gram negative curved rods, non-spore forming, grow well at 42C
bloody diarrhoea, fever
campylobacter species:
types?
associated with?
epidemiology?
incubation/duration?
other important features?
C. jejuni and C. coli
associated with frozen poultry, wild birds, other animals, milk and water
sporadic in developed world, epidemic in non dev
incubation: 24-74 hours
duration: 1 week
commonest cause of diarrhoea in the developed world
Guillain-Barre Syndrome (from toxins)
diagnosis and treatment of campylobacter species?
clinical + stool culture
antibiotics
non-typhi salmonella spp:
where does it act?
infective/intoxication?
features?
diarrhoea/fever?
small and large bowel, infective
gram-negative, non-spore forming, facultatively anaerobic bacilli
can be watery/bloody diarrhoea, +/- fever
non-typhi salmonella spp:
associated with?
epidemiology?
incubation and duration?
other important features?
associated with poultry/eggs (unlike typhi which has only human reservoir)
sporadic and outbreaks
incubation: 6-48h
duration: 1-7 days
often serious. wide range of clinical manifestations. 2nd cause of foodborne disease worldwide.
non-typhi salmonella spp:
diagnosis?
treatment?
clinical + stool culture
antibiotics, MDR!!! (multi-drug resistant)
clostridium perfringens:
where does it act?
infective/intoxication?
features?
diarrhoea/fever?
small bowel, intoxication
aerotolerant, gram-positive rods, forming endospores
watery diarrhoea, +/- fever
clostridium perfringens: intoxication pathway?
associated with bulk cooking of meat
warm food - contamination by spores which germinate
a culture of vegetative bacteria is ingested
bacteria sporulate in small intestine and produce an enterotoxin
destruction of villus tips with resultant pain and diarrhoea (+ myonecrosis)
often large outbreaks
clostridium perfringens:
incubation?
duration?
diagnosis?
treatment?
incubation 8-22h
duration 1-2 days
diagnosis: stool culture + detection of toxin
treatment: supportive
clostridium botulinum:
where does it act?
infective/intoxication?
features?
diarrhoea/fever?
small bowel, intoxication
anaerobic, spore-forming, toxin types A-G
watery diarrhoea, +/- fever
clostridium botulinum: 3 big clinical manifestations?
(botulism = toxin-mediated paralytic illness)
neuro-botulism
foodborne botulism
wound botulism
clostridium botulinum:
associated with?
diagnosis?
treatment?
other important features?
associated with soils, lake sediments, vegetables, GI tract of mammals, birds, fish. home canned or fermented foods.
diagnosis: stool culture + detection of toxin
treatment: supportive
staphylococcus aureus:
where does it act?
infective/intoxication?
features?
diarrhoea/fever?
acts on small intestine, intoxication
gram-positive coccus, aerobe, nonmotile, non-spore forming
watery diarrhoea +/- fever
staphylococcus aureus:
associated with?
incubation?
duration?
clinical features?
other important features?
contaminates salted foods and dairy produce
incubation 2-6h, duration 1-24h
very acute vomiting response often followed with diarrhoea
commonest skin organism, toxins = heat stable
staphylococcus aureus:
diagnosis?
treatment?
diagnosis not necessary
treatment is supportive
bacillus cereus:
where does it act?
infective/intoxication?
features?
diarrhoea/fever?
acts on small bowel, intoxication
aerobic (or facultatively anaerobic), spore forming gram-positive bacilli
watery diarrhoea +/- fever
bacillus cereus:
associated with?
clinical features?
other important features?
spore germinate in warm cooked rice
acute vomit response followed by diarrhoea
resist extreme temperature - form biofilms
spores ingested - vegetative cells - toxins
separate toxins for vomiting and diarrhoea responses
bacillus cereus:
incubation?
duration?
diagnosis?
treatment?
incubation: 1-5h
duration:12-24h
diagnosis: not necessary
treatment: supportive
