Control of GI infections / GI pathogens Flashcards
what are most infections in GI related to? (4)
- cross contamination of work surfaces/utensils
- undercooking (insufficiency heat to kill pathogens)
- improper storage of food (inadequate refrigeration)
- re-heating food
what is clostridium Difficile (C. duffle) a common cause of?
= healthcare associated diarrhoea
how is C. difficile carried?
= as part of normal bacterial flora, particularly in elderly
describe the mechanism of action of C. difficile?
- organisms produce 2 toxins
= toxins A (enterotoxin)
= toxin B (cytotoxin
source/vehicle of infection of C. difficile
- presents in small numbers in bowel
- infection occurs when antibiotics are prescribed that kill off normal competitive bowel flora and allows C difficile to overgrow
what are symptoms of C. difficile?
- diarrhoea, sometimes bloody
- abdominal pain
- severe cases may causes progress to pseudomembranous colitis or bowel perforation
how would you manage C. difficile?
= depends on every
Less severe = oral metrondiazole
Severe = oral vancomycin (for everything else you would give vancomycin IV but not in C. difficile)
how do you prevent C. difficile?
= good anti-microbial prescribing is KEY
= avoid 4C’s and use narrow spectrum antibiotics
- isolating patients, hand washing (NOT GEL) and cleaning of environment
what type of bacteria is C. difficile?
gram positive spore bearing bacillus
= the spores are more resistant to disinfectant
C. difficile what would you see?
= presence of pseudo membrane on surface of colon
how do you diagnose C. diff?
There is no one good lab test;
= screening test for presence of organism (GDH)
= if GDH positive, test for prince of toxin (Toxin A &B)
= toxin will remain positive after 12 weeks after having had C. diff
Results;
- screening type neg = negative result
- screening type positive = positive result
= screening test pos, toxins test negative - indeterminate result
= if repeat is indeterminate = clinical decision required
viruses that cause diarrhoea
rotavirus
norovirus
describe rotavirus
commonest cause of D&V in children < 3years
- most children have it by 5
- person to person spread
- common in winter
- high infectious dose of 100 particles to catch it (highly infectious)
- survives in environment
- billions shed of it in faeces when diarrhoea
what is a consequence of rotavirus?
- decreased absorption of fluids and increased secretion in bowel = dehydration
- post infection malabsorption = causing more diarrhoea
how is diagnosis of rotavirus done?
= PCR test on faeces
how do you manage it rotavirus?
= rehydration is key
when is norovirus very prevalent?
= winter committing disease
what age of people are more likely to get norovirus?
all ages = highly infectious
describe he infectiousness of norovirus?
= 5 billion viruses per gram of faeces
how is norovirus spread?
= faecal-oral/droplet routes of spread
- person to person (or on contaminated food/water)
- environment survival
describe the incubation of norovirus?
= short incubation pardon often < 24hours
- sudden onset explosive D & V, lasts 2-4 day
= vomiting leads to widespread contamination of environment = outbreaks
how do you diagnose norovirus?
- PCR test for faeces specimen or vomit swab
how do you treat norovirus?
= rehydration, particularly in young and elderly
why do you need to stay off work/school for at least 48hours post symptoms?
= because even when you are asymptomatic sheeting still occurs up to 48ours after
when are patients most infectious?
= when symptomatic with diarrhoea
when would diarrhoea indicate infectious?
= fevere
= QUICK onset
when would a patient need a side room?
= C. difficile
= norovirus
when does the patient need admitted to ID unit?
= salmonella
= E. coli 0157
what are other non-diarrhoea infections that are spread by faecal-oral route that?
= hepatitis A&E
- resistant bacteria carried in GI tract e.g. vancomycin resistant enterococci, highly resistant gram negative organisms (CPEs)
Lecture 2 - GI pathogens
Lecture 2 - GI pathogens
True or false.
the gut is full of bugs.
True
describe the lifecycle of bacteria?
- introduced to new environment
- established
- grow and spread
- has an impact
what are the most important gram negative and positive bacteria in the large bowel?
Gram negative
= enterobacteriaecae
- E. coli
- klebsiella spp.
Gram positive
= enterococcus
e.g. E. faecalis
what is the lifecycle of a pathogen?
- exposure
- adhesion
- invasion
- colonisation
- toxicity
- tissue damage and disease
what is colonisation?
= establishment of microorganism on or within a host, may be short lived
what are pathogens?
= any micro-organism with the potential to cause disease
what is virulence?
= the likelihood of causing disease
- opportunistic or accidental pathogen
what 4 tests could be done?
= microscopy: stool, urine, CSF, sputum, pus
= serology
= antien detection
= PCR/molecular studies
what are the different periods involved in invasion by a pathogen?
- incubation period (pathogen replicates in host)
- prodromal period (early signs and symptoms)
- illness period (clinical signs and symptoms)
- convalescent period (signs and symptoms recede; person returns to health)
- host may become chronic carrier of infectious agent
what infections can arise in the abdomen?
- peritonitis (primary & secondary)
- oral infections
- oesophagitis
- gastritis, duodenitis
- hepatitis, liver abces
- cholecystitis, cholangitis
- pancreatitis
- small bowel
- gastroenteritis, abscesses
how do you classify bacteria organisms?
1) shape
- bacilli = enterobacteraecia
- cocci = streptococcus sp, enterococcus ep
- spirochete = helicobacter pylori
2) growth characteristics
- aerobic/anaerobic
= characteristics of growth
= biochemical reactions
describe gram negative rod testing.
enterobacteriecaea - lactose fermenting = e. coli = klebsiella spp = enterobacter spp
- lactose non-formenting
how do you identify bacteria?
1) macroscopic
- colony size
- shape
- pattern haemolysis
2) microscopic
- gram stain
- organism shape
describe the microbiological tests for enterobacteriacaea?
- ferment glucose
= produces acid - blood agar
- MacConkey agar
- CLED agar
- chromogenic agar
describe enterobacteriaecaea?
- gram negative
- non-spore forming
- grow on a variety of solid media
- ferment sugars
- facultative anaerobes mostly
- motile or non-motile
- increasing resistance
how does enterobacteriaecaea cause disease?
1) motility
- flagella allows movement
- shigella and klebbiela are not mobile
2) colonisation factors
- fimbriae
3) endotoxin
- cell wall component
4) enterotoxin
what is a far quicker method of testing bacteria?
MALDI-TOF
what organisms are serotyping important for?
- streptococcus B-hemolytic
- streptococcus pneumonia
- neisseeria meningitis
- E. coli
- Klebsiella
gram positives in mouth
- strep viridian’s
- neisseria sp, anaerobes
- candida sp, staphylococci
gram positives in stomach/duodenum
- normally sterile
= others cause no problems
describe normal bowel flora in jejunum, colonn and bile ducts.
Jejunum
- small number of coliform and anaerobes
Colon
- large numbers of coliform, anaerobes and enterococcus faecalis
Bile ducts
- usually sterile
what is a strict anaerobe?
= a bug that will NoT grow in the presence of oxygen
- clostridium sp, bactericides sp, and anaerobic cocci
where are strict anaerobes present in large numbers?
= in bowel
what is the most import anaerobe
bacteroids
gram positives in mouth
- strep viridian’s
- neisseria sp, anaerobes
- candida sp, staphylococci
gram positives in stomach/duodenum
- normally sterile
= others cause no problems
describe normal bowel flora in jejunum, colonn and bile ducts.
Jejunum
- small number of coliform and anaerobes
Colon
- large numbers of coliform, anaerobes and enterococcus faecalis
Bile ducts
- usually sterile
what is a strict anaerobe?
= a bug that will NoT grow in the presence of oxygen
- clostridium sp, bactericides sp, and anaerobic cocci
where are strict anaerobes present in large numbers?
= in bowel
what is the most import anaerobe
bacteroids
