Infectious Disease Flashcards
what are infectious diseases caused by?
cross contamination, undercooking, improper storage of food and reheating of food
what is the general pathophysiology of organisms
attachment to GI mucosa > cellular invasion > production of exotoxins > changes in epithelial cell physiology > loss of brush border digestive enzymes > inc intestinal motility
what are risk factors for pts becoming infected?
immunosuppression, genetics, bad hygiene, malnutrition, contamination
what are the 6 bacterias responsible for GI infections?
C.Diff, campylobacter, salmonella, listeria monocytogenes, shigella, E.Coli
C.diff epidemiology?
most common cause of diarrhoea
what does c.diff produce and why is it bad?
produce spores that may be resistant to disinfectant
true/false…
c.diff is transmittable
true
some strains of c.diff are _______ of toxins
hyperproducers
what are the 2 toxins that c.diff produce?
toxin A (enterotoxin) toxin B (cytotoxin)
what exacerbates c.diff bacteria already in gut?
antibiotics that kill normal gut flora which allows c.diff to overgrow
symptoms of c.diff infection
bloody diarrhoea, abdominal pain
ix for c.diff?
GDH (if +ve then test for toxins) > if GDH +ve and toxin test -ve assess pt clinically and retest
2 antibiotics given for c.diff
metronidazole & vancomycin
prevention for c.diff?
use narrow spec antibiotics and avoid 4Cs, isolate pts
what are the 4Cs
clindamycin, ciprofloxacin, co-amoxi, clarithromycin
what are possible complications of C.diff?
pseudomembranous colitis and perforation
campylobacter is a gram ___ ____
-ve bacilli
how long is campylobacter’s intubation period?
3-10 days
campylobacter is most common organism that causes…?
gastroenteritis
source of campylobacter?
raw poultry
symptoms of campylobacter?
abdo pain, fever, bloody diarrhoea
what may campylobacter mimic?
appendicitis
tx for campylobacter?
self-limiting, antibis (erythromycin or ciprofloxacin)
complications of campylobacter?
bacteraemia, Guillain-Barre syndrome
what type of organism is salmonella?
colifrom (gram -ve)
is intubation for salmonella long or short?
short-24 to 48hr
why is salmonella dangerous?
produces toxin and is invasive
source of salmonella?
poultry, meat, raw egg
pathophysiology of salmonella?
born in animal gut and multiplies in food
symptoms of salmonella?
diarrhoea & vomit, bloody?, fever, abode pain
salmonella typhoic is a strain of salmonella- what is its common presentation?
rose spots on abdomen
tx for salmonella?
same as campylobacter ie. Antibes are erythromycin and ciprofloxacin
Listeria Monocytogenes is a gram __ bacterium
+ve
true/false…
intubation of LM is long
false..
it is short (9-48hrs)
listeria monocytogenes thrives in …?
cold e.g. fridge
symptoms of listeria monocytogenes?
fever, muscle aches, diarrhoea
source of Listeria Monocytogenes?
unpasteurised milk, deli counter
transmission of listeria monocytogenes?
food Bourne, mother to child
shigella is gram __?
-ve
how long is Shigella’s intubation?
1-9 days
what kind of toxin does shigella release?
shiga toxin
how does shiga toxin work?
binds to renal cell receptors (RBC etc) and inhibits protein synthesis causing cell death
which of the shiga toxins is more potent?
shiga toxin 2
who does e.coli usually affect more?
children
pathogenesis of e.coli?
adhere to epigastric cells and elaborate shiga toxin which inhibits proton synthesis resulting in death of enterocytes and endothelial cells > this activates inflammatory response causing fibrin deposits and clot formation > hameturia is caused
symptoms of e.coli?
bloody diarrhoea, high WBC, low Hb
tx for e.coli?
supportive
complications of e.coli?
renal failure
types of e.coli…
e.coli 0157 enterotoxigenic enteropathogenic enteroinvasive enteroaggregative
intubation of e.coli 0157?
1-14 days
what toxin is produced with e.coli 0157?
verotoxin (kidney damage > HUS)
symptoms of 0157?
blood diarrhoea, fever pain
main complication of e.coli 0157?
Haemolytic Uraemic Syndrome (HUS)
epidemiology for HUS?
<16 yo, elderly
ix for HUS?
stool sample, bloods (high WBC, low platelets & Hb)
why is HUS an emergency?
can easily progress to acute renal failure, thrombocytopenia, haemolytic anaemia
which 2 e.coli’s are mostly associated with travel?
enterotoxigenic and enteroaggregative
true/false…
amoebas are responsible for outbreaks on cruise ships
false…
usually viruses- rota & noro virus
rotovirus is no1 culprit for what presentation in young kids (<3)?
diarrhoea and vomiting
what type of spread does rotavirus have?
faecal-oral
how long does rotavirus last?
1 week
true/false…
adults are affected more badly that kids by rotavirus
false…
kids are more badly affected
symptoms of rotavirus?
diarrhoea with NO BLOOD
source of rotavirus?
contaminated drinking water, food, fomites
ix for rotavirus?
PCR
tx for rotavirus?
self-limiting, rehydration, vaccine
complications of rotavirus
post-infection malabsorption or repeat infections
what is norovirus presentation like
explosive vomiting
norovirus spread?
faecal-roal or droplets
how long is norovirus incubation?
2-4 days
what should be noted for fomites of norovirus?
asymptomatic shedding of virus for up to 48hrs post cessation of symptoms
true/false…
like rotavirus, nor virus mainly affects kids
false…
affects all ages
source of norovirus?
contaminated food or water
ix for norovirus?
faeces or vomit for PCR
tx for norovirus?
rehydration, self limiting
how to control infection in hospital setting?
standard infection control precautions, contact precautions, prudent antibiotic prescribing
spread of entamoeba histolytica?
faecal-oral
symptoms of entamoeba histolytica?
asymptomatic, abdominal pain, fever, acute, bloody diarrhoea, tenderness peritonism
ix for entamoeba histolytica?
stool for custs/ trophozoites, AXR (exclude toxic megacolon), endoscopy w biopsy
common complication of entamoeba histolytica?
amoebic liver abscess
epi for amoebic liver abscess?
intubation is 8-20 days, more common in men
s/s of amoebic liver abscess?
sub-acute: 2-4 weeks (fever, sweats, upper ab pain, GI upset, hepatomegaly, tenderness over right lower ribs)
ix for amoebic liver abscess
LFTs, CXR (opacity over right lung base), USS, CT
tx for amoebic liver abscess?
metronidazole/ tinidazole
4 types of protozoa
- giardiasis
- helminths
- chugs disease
- enterobius vermicularis
what is giardiasis causing organism?
flagellated protozoa
source of giardiasis?
contaminated water
sites of giardiasis infection?
duodenum and proximal jejunum
symptoms of giardiasis?
explosive watery diarrhoea, bloating, ab cramps, wt loss
ix for giardiasis?
stool microscopy-cysts seen, PCR, OGD (oesophagus-gastro- duodenoscopy)
tx for giardiasis?
metronidazole
helminth infection site?
in gut and tissue
signs of helminths infection?
eosinophilia, adult worm passed or eggs in stools
what are 3 types of helminths?
nematodes, trematodes, cestodes
nematodes are also known as?
intestinal roundworms
pathogenesis of nematode infection?
egg ingested > hatches in small intestine > invades gut walls and reaches venous system > breaks into lung and alveoli > goes into bronchial tree and then swallowed into gut where becomes worm
true/false…
schistosomiasis is caused by nematodes
false…
by trematodes
what is a complication of schistosomiasis
can lead to hepatomegaly, liver fibrosis or PHTension
where do cestodes originate in?
pork or beef that is undercooked and contains larval cysts
what are cestodes also known as?
tapeworms
a common complication of tapeworms is…
cysticercosis- tissue cysts in muscles and brain
what is the organism that causes chagas disease?
trypanasoma cruzi
transmission of chagas?
kissing bug (triatome)
what is chagas disease?
causes parasympathetic denervation affecting colon and oesophagus
what is Enterobius vermicularis?
threadwormss- tiny white worms in stool
classic epidemiology of threadworms?
children
s/s of threadworms?
perianal itch, worms in stool
pathogenesis of threadworms?
eggs ingested > hatch in intestine > live in caecum/colon > adult females exit onto perianal skin and lay eggs > itchy so scratch and then fingers in mouth again
how does enterobius vermicularis spread?
person to person- human only disease
tx for threadworms (enterobius vermicularis)?
oral mebendazole
what is gastroenteritis
infection of large intestine
what microbiomes are responsible for gastroenteritis
campylobacter, shigella, e.coli, entamoeba histolytica
what is the most common bacteria that causes gastroenteritis?
campylobacter
duration of gastroenteritis?
< 2 weeks
aetiology of gastroenteritis?
contaminated food, toxins, poisons
symptoms of gastroenteritis?
diarrhoea & vomiting, abdominal pain
important hx to take note of when pt presents with gastroenteritis?
travel, food hx e.g. reheating, contact tracing, antibiotics?
ix for gastroenteritis?
stool sample - takes 48hrs
complications of gastroenteritis?
many organisms that cause gastroenteritis invade other tissues and produce toxins
intubation for gastroenteritis?
very short- 1 to 6hrs
what type of organism thrives when reheating rice?
gram +ve bacillus e.g. bacillus cereus
what is main presentation of bacillus cereus?
profuse vomiting
what organisms thrive when food is left out at room temp e.g. milk, fish etc
gram +ve cocci e.g. staphylococcus aureus
3 factors that allows bacteria to multiply?
time, temp and moisture
what 2 micro organisms are responsible for viral gastroenteritis?
rotavirus & norovirus
ix for viral gastroenteritis?
stool sample- PCR, antigen detection, serology, immunoassay
if a returned traveler presents in A&E feeling unwell, what must you do straight away?
isolate, have a full comprehensive travel hx e.g. accommodation, since bites etc, s/s
what are some ddx’s for returned traveler presenting with fever?
resp tract infection (pneumonia, influenza), traveller’s diarrhoea, malaria, enteric fever (typhoid), arboviruses (Dengue, Zika)
what is the definition of acute traveller’s diarrhoea?
3 loose stools in 24 hrs
micro organisms responsible for acute traveller’s diarrhoea?
enterotoxigenic E.Coli, campylobacter, salmonella, shigella, viruses?
important acute traveler’s diarrhoea’s are…
cholera (watery diarrhoea, refugee camps)
dysentery (bloody diarrhoea caused by e.coli 0157)
ix for acute traveller’s diarrhoea?
stool culture
tx for acute traveller’s diarrhoea?
supportive, rehydration therapy, macrolide
where is enteric fever most commonly found in?
india and SE asia
incubation for enteric fever?
7-18 days
types of enteric fevers?
typhoid and paratyphoid
symptoms of enteric fever?
fever and non-specific symptoms e.g. headache
main organism responsible for enteric fever?
salmonella
ix for enteric fever?
blood tests, stool, urine
tx for enteric fever?
ciprofloxacin, azthromycin, vaccines
complications of enteric fever?
GI bleed, GI perf, encephalopathy, other infections
main causes for pre-hepatic jaundice in returned travellers?
malaria, HUS, sickle cell crisis triggered by infection
main causes for hepatic jaundice in returned travellers?
hep A&E, leptospirosis, malaria, enteric fever
main causes for post- hepatic jaundice in returned travellers?
ascending cholangitis
ix for fever and jaundice in returned travellers
USS abdomen, bloods (FBC,LFT,coags, serology)
tx for fever and jaundice in returned travellers
supportive (dialysis?), liver transplant worst case scenario
