GI Infections Flashcards
host defences of the mouth
flow of liquids
saliva
lysozyme
normal bacterial flora
host defences of the oesophagus
Flow of liquids
Peristalsis
host defences of the stomach
acid pH
host defence of the small intestine
Flow of gut contents Peristalsis Mucus, bile Secretory IgA Lymphoid tissue (Peyer’s patches) Shedding and replacement of epithelium Normal flora
host defence of the large intestine
Normal flora
Peristalsis
Shedding and replication
mucus
what is the role of the bacteria in the stomach and colon?
Selectively inhibit gastroenteritis from occurring on daily basis
is it worthwhile taking products with probiotics
no
Most bacteria from probiotics die in stomach before they reach colon – where they are meant to work
what are the majority of good bacteria like
99.9% anaerobes e.g. Bacteroides fragilis
E. coli
what is a purpose of good bacteria in the GIT
Good bacteria make supplementary vitamins (secondary metabolites)
- Vitamin K production
Needed to make cascade system required for absorbing nutrients
3 types of causative agents
bacteria
viruses
protozoa
helicobacter pylori is associated with which diseases
Assoc. with 90% of duodenal ulcers
Assoc. with 70-80% of gastric ulcers
Increased risk of gastric cancer (adenocarcinoma)
- Kills many
how does helicobacter pylori survive and be virulent
Ability to survive in acidic conditions
Catches to epithelial cell
Releases enterotoxins
Endothelial release neutrophils as lumen is agitated
- If sustained can lead to cancer
what area of the world is more effected by H pylori
50-90% of developing world infected
- crammed environments
In developed world there is low prevalence
Associated with socio-economic factors
mode of transfer of H pylori
Mode of transfer undefined
Transmission probably faecal-oral route
Oral-oral route also implicated
pathogenicity of H pylori
Acid tolerance
- Turn acid into urea which causes ammonia production
- Detoxifies the acid so bacteria can thrive
Ammonia is in breath test
3 methods of diagnosis for H pylori
endoscopy and biopsy (more invasive)
breath test
serology
3 methods of treatment for Gi infections
Proton pump inhibitor
Bismuth salts
Antibiotics (combination)
- Amoxicillin
- Clarithromycin
- Metronidazole
what is gastroenteritis
non-specific term for various pathologic states of the gastrointestinal tract
- body takes in something which it subsequently tries to secrete/excrete
The primary manifestation is diarrhoea, but it may be accompanied by nausea, vomiting, and abdominal pain
definition of diarrhoea
universal definition does not exist
Definitions centre on:
- Frequency, consistency, and water content
- Disease of the small intestine and involving increased fluid and electrolyte loss
key symptoms of viral gastroenteritis (6)
abdominal cramps (1)
Vomiting
Profuse watery stools
Myalgias
- Sore head due to interferon
Fever
Headaches
key symptoms of bacterial dysentery (5)
Small volume stools Fever Tenesumus Bloody mucoid stools suprapubic pain
exotoxin stimulating enterocytes in number of different ways
what is the most common causative agent for gastroenteritis
viral (50-70%)
Norovirus, Caliciviruses, Rotavirus, Adenovirus, Parvovirus, Astrovirus
what is the second most common causative agent for gastroenteritis
bacterial (15-20%)
Salmonella, Shigella, and Campylobacter species
what is the least most common causative agent for gastroenteritis
parasitic (10-15%)
Giardia lamblia, Entamoeba, Cryptosporidium
invasive infection
The organism enters the mucosal cells, destroys them, causing diarrhoea usually with blood in the stool
enterotoxic infection
The organisms do not invade the mucosa, but produce enterotoxins of which act as chemical mediators causing hypersecretion of the fluid. - - - Little damage to the tissue is done.
Produces proteins which cause a physiological response
structure of norovirus
non-enveloped RNA virus (calciviridae)
transmission of norovirus
aerosolised particles end up a distance away
- variety of different episodes
projectile vomiting
how contagious is norovirus
very
10-100 particles needed for infection
incubation period for norovirus
1-2 days approx
clinical manifestation of norovirus
abrupt onset of vomiting & watery diarrhoea +/- fever and abdominal pain (similar to rotavirus).
management of norovirus
self-limiting;
correct fluid / electrolyte balance.
can norovirus have repeated infections
yes
strain specific immunity only lasts a few months.
can norovirus survive in the environment
Very resilient in the environment
Have to be diligent in cleaning procedures – can self perpetuate
3 types of salmonella
- Gastroenteritis is most common form of Salmonellosis
- Enteric Fever- Typhoid Fever
- Bacteremia
how can a pt contract salmonella
Eating foods produced from infected animals; meat, milk, poultry, eggs, and drinking contaminated water; and from fecal-oral trans.
incubation period for salmonella
8-48 hrs
signs/symptoms of salmonella
can be asymptomatic
or after 2 days of eating infected food - Cramps - Watery or bloody diarrhoea - Fever - sometimes vomiting Lasts 1-4 days
how to diagnose salmonella
stool, Presence of fecal WBC’s variable
how to treat salmonella
supportive (IV hydration)
Antibiotics usually not necessary for Salmonella gastroenteritis (Bactrim, Amp, or Cipro indicated in pt’s c increased risk of mortality, Typhoid fever, or Bacteremia)
when and where was the first recognised UK hospital C.diff outbreak
Stoke Mandeville Hospital, Aylesbury 2003
- Over 3 month period
150 cases
12 deaths
how can a pt get C.diff
common cause of nosocomial antibiotic-associated diarrhea (AAD)
- over prescribing
- Only contract when over exposed to antibiotics
- Broad spectrum antibiotics get rid of competitive inhibition
Lying but start to thrive
Most common infectious cause of acute diarrheal illness in LTCFs
- Unnecessary disease
- Poor standards of health care lead to C.diff outbreak
unique features of c.diff
anaerobic and forms spores
survive> 5 months and hard to destroy
what is the infective dose of C.diff
less than 10 spores
risk factors for CDI
Exposure to antimicrobials (prior 2-3 months)
Exposure to healthcare (prior 2-3 months)
Infection with toxogenic strains of C. difficile
Old age > 64 years
Underlying illness
Immunosuppression & HIV
Chemotherapy (immunosuppression & antibiotic-like activities)
Tube feeds and GI surgery
Exposure to gastric acid suppression meds ??
microbiology features of C.diff
Gram positive spore forming bacillus (rods)
Obligate anaerobe
Part of the GI Flora in
- 1-3% of healthy adult
- 70% of children < 12 months
Some strains produce toxins A & B
- Both damaging to enterocytes in colon
Toxins-producing strains cause C. diff Infection (CDI)
CDI ranges from mild, moderate, to severe and even fatal illness (35% mortality)
- Hard wearing, chestnut spores
transmission of C Diff
Faecal – oral route
- Contaminated hands of healthcare workers
- Contaminated environmental surfaces.
High level of disinfection needed
Person to person in hospitals and LTCFs
2 reservoirs of C diff
Human: colonized or infected persons
Contaminated environment
3 clinical manifestations of C diff
Illness caused by toxin-producing strains of C. difficile ranges from
- Asymptomatic carriers = Colonized
- Mild or moderate diarrhoea
- Pseudo membranous colitis that can be fatal
3 time scales of which pt can contract C diff
Acquire in hospital
Or arrive with
Or leave asymptomatic and return
- Spores in colon already and then become susceptible
median time between exposure to onset of CDI symptoms
2–3 days
5 symptoms of CDI
Watery diarrhoea ( > 3 unformed stools in 24 or fewer consecutive hours)
Loss of appetite
- Become malnourished
- -May fail to communicate this
Fever
Nausea
Abdominal pain and cramping
CDI pathogenesis
Changes in intestinal microbiota
- Organisms flourish
Produces A and B toxin
pseudomembranous colitis
Consequence of immune response
Plaque are inflammatory infiltrate
- Cannot absorb nutrients
- Sections need resected
Irreversible
- Not resume to normal pathology
4 treatments of CDI
Oral rehydration
Antibiotics
- Metronidazole, vancomycin Probiotics
- despite being caused by antibiotics
Colectomy
Faecal transplants
- Works but unpleasant
- Revert microbiome to that of close family member
case definition of CDI
Clinical: presence of diarrhoea AND
Laboratory: A stool test result positive for toxigenic C. diff or its toxins OR colonoscopic / histopathologic findings demonstrating evidence of pseudomembranes
4 ways to try and prevent GI infections
Use of statutory powers
- Norovirus outbreak – in pt or staff – practicing dentist needs to self exclude
Safe food handling & handwashing
Infection control – enteric precautions for diarrhoea & vomiting
- SICPs
- Barrier nursing/patient isolation
Missuse of antibiotics
- Esp in elderly pt groups
- Surveillance
