GI - microbiology Flashcards
what is the first line treatment of gastroenteritis
rehydration
what is gastroenteritis
inflammation of stomach/intestines
what organisms are the most common cause of infective gastroenteritis
viruses
how do bacteria cause GE
invade tissues of GI tract and produce toxins
define diarrhoea
3+ loose stools in 24 hours
stool holds shape of container
what is considered acute diarrhoea and what is chronic
acute < 2 weeks
chronic > 4 weeks
What kind of infection is Giardia Lambia
protozoan - single parasite infection
cysts are ingested and hatch into trophozoites
trophozoites colonise upper small bowel mucosa
How is giardia lambia spread
cysts in water
travel to areas of contaminated water supply
swimming in ponds
can giardia lambia be spread person-person
yes
- also, human only infection
how is giardia lambia diagnosed
Lab: stool microscopy for ova/parasites/cysts
3 separate samples
duodenal aspirate is best
what is the treatment for giardia lambia
metronidazole 1 week
diarrhoea (often explosive, foul smelling) flatulence anorexia abdominal cramps epigastric pain nausea vomiting malabsorption (steatorrhoea, weight loss)
symptoms of giardia lambia
give 2 organisms that cause small bowel bacterial overgrowth
E.Coli
Bacteriodes (gram negative, anaerobic, bacilli)
how is SBBO diagnosed
low cobalamin and high folate
culture on jejunal aspirate obtained by intubation - aerobic +/- anaerobic bacteria present
Schilling test
what is the treatment of SBBO
tetracyclines (2-3 weeks)
surgical correction
when is SBBO seen
diverticula fistulas strictures related to Crohn's bypass surgery functional stasis
diarrhoea
steatorrhoea
macrocytic anaemia
symptoms SBBO
what food is scombroid associated with
dark meat/fish in tropical areas tuna mahi mahi sushi tinned tuna poorly stored fish
Scombroid involves a preformed toxin
true/false
true
what is the incubation period of scombroid
1-6 hours
what kind of reaction is scombroid poisoning
histamine like reaction
rash, headache, shock
what is T1 on the bristol stool chart
separate hard lumps like nuts
hard to pass
what is T2 on the bristol stool chart
sausage shaped but lumpy
what is T3 on the BSC
like a sausage but with cracks on surface
T4 BSC
like a sausage or snake
smooth and soft
T5 BSC
soft blobs with clear cut edges
passed easily
T6 BSC
fluffy pieces with ragged edges, a mushy stool
T7 BSC
water, no solid pieces
entirely liquid
what is the incubation period of staph aureus, bacillus cerues
1-6 hours
short
what is the incubation period of salmonella, C. perfringens
12-48 hours
medium
what is the incubation period of campylobacter, E. Coli 0157
2-14 days
long
(16-48 hours usually)
what is the most common cause of diarrhoea in the UK
campylobacter
campylobacter is…
curved
gram negative
bacilli
what is the source of campylobacter
you CAMP at a farm farm animals - esp undercooked poultry milk products cheese water
what is a complication of campylobacter
gillian barre
what is gillian barre
immune system attacks PNS - tingling of feet progresses to paralysis
how are outbreaks of campylobacter caused
people exposed to the same source
i.e. not human - human
central abdominal pain
diarrhoea +/- blood
may mimic appendicitis
symptoms of campylobacter
how is campylobacter diagnosed
stool culture
what is the treatment of campylobacter
self limiting
clarithromycin if immunosuppressed
erythromycin or ciprofloxacin if systemic illness
what are some s/s that campylobacter has caused a systemic illness
fevers
rigors
flu-like symptoms
salmonella is ….
gram negative
bacillus
enterobacteria
who is at risk of bacteraemia from salmonella
HIV
sickle cell
AIDs
recent cryptosporidium
what antigen does salmonella possess
O antigen
what is the source of salmonella
undercooked poultry
raw eggs
less common due to chicken immunity
what is the treatment of salmonella
self limiting
ciprofloxacin 5 days if systemic illness/risk of
what is the incubation period of salmonella
12-48 hours
how is salmonella diagnosed
stool culture
where does salmonella cause inflammation
ileum and colon
salmonella grows in animal gut and multiplies in food - then multiply in gut and cause mucosal damage - decreasing fluid absorption and increasing fluid secretion
where does campylobacter cause inflammation
colon and rectum
how does salmonella cause GE
invades tissue of GI tract and produces toxin
abdominal pain
diarrhoea (occasionally bloody)
vomiting
s/s salmonella
can shigella spread person-person
yes
also - human only infection
how is shigella diagnoses
stool culture
why is shigella not seen in blood cultures
invades intestinal mucosa and causes severe inflammation but no further
what is the treatment of shigella
ciprofloxacin if severe
what is a complication of shigella
HUS
where is shigella often seen
cohorts of children
can salmonella cause outbreaks
yes
shigella is…
gram negative
what is the incubation period of E. Coli
16 - 48 hours
what kind of antigen does E. Coli possess
O antigen on surface
E. Coli is …
gram negative
coliform
what toxin does E. Coli produce
verotoxin (VTEC) (shiga-like toxin)
how does VTEC work
binds to cell receptors found on renal and red blood cells
inhibits protein synthesis and causes cell death
what is a major complication of E. Coli
HUS
what should be avoided in HUS
antibiotics
NSAIDs
anti motility agents
what is HUS
haemolytic uraemic syndrome - increased blood urea, red cell haemolysis, thrombocytopaenia
pre-hepatic jaundice
what are some s/s of HUS
abdominal pain petechiae fever pallor BLOODY DIARRHOEA (e.coli in general) oliguria
what is petechiae
small haemorrhage of blood vessels
what is the source of E. Coli
beef minced meat burgers (not so much steak) raw milk soy nut butter visits to farms private untreated water sources
can E. coli be spread person - person
yes
can E. coli cause outbreaks
yes
who is most at risk of HUS
children and elderly
E. coli is the commonest cause of renal failure in children <5 in the UK
true/false
true
what do the bloods of E.Coli show
increase WCC low platelets low Hb RBC fragments increased LDH
does e.coli 0104 produce verotoxin
yes but less toxic
what does VTEC show in agar
agglutination
what is the treatment of E. Coli
supportive
NO ABs
what is the cause of enteric fever/typhoid/paratyphoid fever
salmonella typhi
salmonella paratyphi A and B
fever initially then diarrhoea (green) fever and rigors headache rose spots on abdomen constipation dry cough
s/s enteric fever
what is the treatment for enteric fever
depends on sensitivities
azithromycin (uncomplicated)
ceftriaxone IV (severe)
possibly fluoroquinolone e.g. ciprofloxacin but resistance common
what are some complications of enteric fever
GI bleeding
GI perforation
encephalopathy
bone/joint infection - osteomyelitis
how is enteric fever diagnosed
blood culture
what is the incubation period of salmonella type/paratyphi
14-21 days
when is enteric fever seen in the UK
when imported from india, SE asia, far/middle east, Africa