Lower GI Infection Flashcards
(30 cards)
define gastroenteritis
syndrome characterised by GI symptoms including nausea, vomiting, diarrhoea or abdominal discomfort
define enterocolitis
inflammation involving mucosa of small and large intestine
define dysentery
blood/pus in stools, usually with abdominal pain and fever
define diarrhoea
frequent fluid-like stool (over 3x a day)
what are the manifestations of GI infections?
within GI tract:
- toxin effects (cholera)
- inflammation (microbial invastion/shigellosis)
outwith GI tract:
- systemic toxin effects (STEC)
- invasive infection (metastatic salmonella)
what are the barriers to GI infection?
mouth (lysozyme)
stomach (acidic pH)
SI (mucous, bile, secretory IgA, peyers patches)
LI (epithelial turnover, normal flora)
describe the normal GI tract flora
rich microbiome (100b microbes per gram of faeces)
99% anaerobes
many facultative organisms (enterobacteriales)
protective/metabolic function (carb/protein/fat breakdown)
what are the sources of GI infections?
zoonotic - symptomatic animals (salmonella) or asymptomatic shedders (E.Coli)
human carriers (typhoid)
environment/soil contamination (listeria)
how are GI infections transmitted?
faecal-oral
food
fluids
fingers/hands
person-to-person
describe diagnostics of GI infections
enrichment broth (nutrients promote pathogen growth)
selective media (suppress growth of background flora)
differencial media (pathogen activates indicator)
describe the general treatment of GI infections
mild - mostly resolves itself
(hydration maintenance)
more severe/immunocompromised - antibiotics (may have adverse effects)
describe the microbiology and epidemiology of salmonella (enterica)
- gram -ve bacilli
- enterobacteriales family
- non lactose fermenters
- XLD plates used in clinical labs
- found in cold/warm blooded animals
- spread through contaminated food (pork/chicken)
- sometimes water-borne
- secondary P2P spread possible
- seasonal peaks (summer/autumn)
describe the pathogenesis and clinical implications of salmonella
diarrhoea (invasion/inflammation of SI epithelia)
distant organs may receive metastasis
- incubates for 12-72h
- diarrhoea, vomiting, fever (2-7 days)
fluid replenishment sufficient mostly
describe the microbiology and epidemiology of campylobacter
- curved gram -ve bacilli
- microaerophilic and thermophilic
- C.jejuni most important
- common foodborne infection
- large animal resevoir (cattle/sheep)
- season peaks (may/sep)
- in 70% of retail chicken
describe the pathogenesis and clinical implications of campylobacter
inflammation/ulceration/bleeding in SI/LI (bacterial invasion)
bacteraemia can occur (age/IC)
guillain-barre demyelination after (rare)
- incubation 2-5 days
- bloody diarrhoea, abdominal cramps, fever (2-10 days)
fluid replenishment sufficient
clarithromycin/erythromycin (severe)
explain the microbiology and epidemiology of E.Coli
- gram -ve bacilli
- enterobacteriales family
- 6 diarrhhoeagenic groups
- non-sorbital fermenter (0157)
- no differencial media available
- outbreaks/sporadic cases worldwide
- ‘travellers diarrhoea’
- infants/children common (developing)
describe the pathogenesis and clinical implications of E.Coli
- adherence on lesions/pili
- action of 1/2 encoded plasmid toxins (ETEC)
- incubation 1-7 days
- diarrhoea (blood - EHEC), abdominal pain, vomiting, fever (EPEC), 5-10 days
- acute renal failure (children, rare)
what viruses cause gastroenteritis?
norovirus/sapovirus (calciviridae) - affects all ages
rotavirus/adenovirus/astrovirus - mainly affects under 2s, elderly and immunocompromised
describe the microbiology of norovirus
non-enveloped, single stranded RNA
10 genogroups (G1-10) - only 1/2/4 affect humans
genogroups -> 48 genotypes
common - GII-4
describe the epidemiology of norovirus
faecal-oral, food, water transmission
small infectious dose (10-100 virions)
1-2 days incubation (shed 3 weeks after infection)
stable (viable for long time)
immunity lasts 6-14 weeks
what are the clinical features of norovirus?
can be asymptomatic
vomiting, diarrhoea (non bloody), nausea, abdominal cramps, headache/muscle ache, fever, dehydration
lasts 1-5 days
what are some possible complications of norovirus?
significant portion of childhood hospitalisation
chronic diarrhoea/virus shedding in transplant patients
post-infection complication risk in elderly
what are the main treatments for norovirus?
oral/IV fluids
antispasmodics
analgesics
antipyretics
describe the microbiology and epidemiology of rotavirus
double stranded, non enveloped RNA virus
5 strains (G1/2/3/4/9) G1 70%
11 RNA strands (variation)
low infectious dose (10-100 virions)
mainly P2P/faecal-oral
shedding in stool up to 10 days
food/water/resp transmission is possible
