1
Q
symptoms of acute gastrointestinal illnesses
A
- vomiting/nausea
- watery, bloody and repetitive diarrhea
- abdominal pain
- fever
2
Q
what is vomiting and nausea associated with acute gastrointestinal illnesses caused by
A
intoxications
3
Q
how can you get acute gastrointestinal illnesses
A
- bacterial infections
- viruses
- protozoans/parasites
- toxins
4
Q
what are the bacterial causes of acute gastrointestinal illnesses
A
- vibrio cholerae
- campylobacter jejuni
- clostridioides difficile
5
Q
what are the sources you can contract vibrio cholera
A
- contaminated food
- contaminated water
- direct or indirect contact with human/animal faeces
6
Q
where did diarrhoea rank in top 10 causes of global death in 2019
A
8th
7
Q
where did diarrhoea rank in top 10 causes of disability-adjusted life years in 2019
A
5th
8
Q
how many children die every year from diarrhoea
A
525,000 children under 5
9
Q
how many cases of childhood diarrhoea are there globally every year
A
1.7 billion
10
Q
how many cases of cholera are there every year
A
1.3 to 4 million
11
Q
how many cases of cholera cause death every year
A
20,000 to 140,000
12
Q
how many cases of diarrhoea does rotovirus cause yearly
A
~19 million
13
Q
how many deaths does diarrhoea by rotovirus cause yearly
A
129,000 in children younger than 5
14
Q
how many cases of diarrhoeal disease in NZ have been caused by cholera recently
A
0-1
15
Q
symptoms of diarrhoea caused by cholera
A
moderate dehydration:
- decreased urine output
- rice-water stools
- headache
- dry skin
- thirsty
- tired
16
Q
what are rice-water stools
A
- a symptom of diarrhoea caused by cholera
- it is watery diarrhoea that looks like water after you’ve washed rice in it
17
Q
where is cholera naturally found
A
- shellfish in coastal waters
- human carriers
18
Q
how is cholera transmitted
A
- we can consume contaminated shellfish
- contact of feces from human carriers
19
Q
what types of human carriers of cholera are there
A
- symptomatic
- asymptomatic
20
Q
how was cholera introduced to haiti
A
- through earthquake aid workers coming from a country where cholera was endemic
- breakdown of sanitisation infrastructure led to contamination of the water supply by their feces
- the contamination of water spread the toxin even more
21
Q
what is an infectious dose of cholera
A
- 10⁵-10⁸
- however 10³ works for children or those who eat less (stomach acid produced less)
22
Q
what is the cholera incubation period
A
12 hours - 5 days
23
Q
what happens after cholera passes through the stomach
A
1) it colonises the intestines via a pilus attachment called TCP
2) it releases an AB₅ toxin that stimulates chloride secretion in the intestines
3) this secretion results in secretory diarrhoea
24
Q
describe the toxin released by cholera
A
- its an AB₅ toxin
- stimulates chloride secretion in the intestines
- A = activity
- B = binding
25
describe the process of the AB₅ toxin entering the intestine
1) the B subunit binds to its receptor in an intestinal cell
2) the toxin is taken up into an endosome then released into the cell cytoplasm
3) it causes the production of cAMP
4) cAMP reduces the uptake of sodium and potassium and increases the secretion of chloride ions and water
5) this leads to the watery diarrhoea
26
how much vomit does someone infected with cholera do
1-2L/day
27
how much rice water stool does someone infected with cholera do
up to 20L/day
28
how is cholera diagnosed
- look for rice water stools
- isolate Vibrio cholera on agar via feces sample
- gram staining
- PCR
- RDTs
29
what agar is Vibrio cholera grown in
TCBS agar
- selective for vibrio
- differentiates for vibrio cholera as it ferments sucrose which turns the agar yellow
- results show after overnight incubation!
30
how does gram staining help to identify Vibrio cholera
the gram-stain should show red (gram-negative) curved rods (comma-shaped)
31
how long does a PCR reaction to identify Vibrio cholera take
results show after a couple hours
32
how do RDTs help to identify Vibrio cholera
1) take a sample of the patient's stool
2) use immunochromatographic tests to detect the LPS O-antigens (O1 and O139)
33
what's a downside of RDTs to identify Vibrio cholera
high rate of false negatives
- results in 20 minutes
34
what are the treatment aims for someone with cholera
- major: dehydration (oral rehydration therapy)
- then: prevent further spread (good hygiene, improved sanitation)
35
what are the treatment aims for someone with severe dehydration
- severe dehydration causes shock
- patient is treated with intravenous fluids
36
what are the treatment aims for someone with moderate dehydration
- oral rehydration therapy
- drinks with clean water containing salt and sugar
37
what's the purpose of oral rehydration therapy
the drink's contents are absorbed in the small intestines to replace the water and electrolytes lost in feces
38
when are antibiotics recommended for cholera
- severe cases
- moderate cases in an epidemic
39
what antibiotic is recommended for cholera
- doxycycline
- kills V. cholera and is cheap
40
when and how is doxycycline taken
- taken orally
- during vomiting phase
41
what does doxycycline do aside from killing V. cholera
- reduces duration of symptoms
- reduces need for ORS/clean water
- reduces shedding and transmission
42
how can cholera be prevented
- safe drinking water
- good sanitation
- good personal and food hygiene
- good nutrition
- vaccines
43
what's the most major microbial cause of diarrhoeal disease NZ
campylobacteriosis
44
how many cases of diarrhoeal disease in NZ have been caused by campylobacteriosis recently
5000-6000
45
what's a major symptom of campylobacteriosis induced diarrhoea
bloody diarrhoea
46
what's the first thing that happens when you visit the doctor for campylobacteriosis induced diarrhoea
a stool sample is sent for:
- microscopy
- microbial cultures
- culture-independent diagnostic testing
- PCR
47
what kind of disease is campylobacteriosis induced diarrhoea
- food poisoning (gastroenteritis)
- meaning it resolves on its own in a matter of time
48
what are the main treatments for gastroenteritis
- fluid + electrolyte replacement
- pain relief
- and an emphasis on hygiene as feces contains the pathogen
49
how long does it take for gastroenteritis to resolve
10 days
50
what kind of drug is not recommended for campylobacteriosis induced diarrhoea
- anti-diarrhoeal drugs are not recommended
- unless you have "flowy" or "watery" diarrhoea
- and unless accompanied with antimicrobial therapy
51
why aren't anti-diarrhoeal drugs recommended
- they can concentrate toxins/pathogens in the gastrointestinal tract
- this increases contact time with the intestinal mucosa
52
what do antibiotics do for campylobacteriosis induced diarrhoea
- reduce severity
- reduce duration
- but also affect good bacteria
53
are antibiotics used against campylobacteriosis induced diarrhoea
no, they are rarely effective against diarrhoea
54
in what cases are antibiotic recommended for campylobacteriosis induced diarrhoea
if the diarrhoea is:
- severe
- prolonged
- there is a risk of or an actual spread to the blood
55
if antibiotics are recommended for campylobacteriosis induced diarrhoea, what kind are they
- macrolides
- e.g. azithromycin or erythromycin
- however increasing levels of resistance have been seen towards campylobacter
56
describe the results of stool microscopy for campylobacteriosis induced diarrhoea
not highly definitive because diarrhoea will contain many other bacteria from the colonic flora
- darkfield or phase-contrast microscopy: demonstrates their characteristic darting motility
OR
- gram-stain: gram-negative, stool shows slim, short curved rods
57
describe the results of PCR test for campylobacteriosis induced diarrhoea
come back positive for Campylobacter jejuni
58
what are the conditions of the agar that the stool sample for campylobacteriosis induced diarrhoea is grown in
conditions ideal for campylobacter growth:
- blood agar containing antibiotics that reduce emergence of other enteric microorganisms
- microaerophilic: incubated at low o2 high co2 conditions
59
describe the results of culture test for campylobacteriosis induced diarrhoea
- positive for Campylobacter jejuni
- water droplet like colonies appearing after 24-48 hours
- other agars for bacterial pathogens are negative
60
what is the food hygiene advice for campylobacteriosis induced diarrhoea
- cook food thoroughly (meat juices run clear not red)
- reheat thoroughly
- clean and separate utensils between food
- refrigerate food
- place cooked meats and salads *above* uncooked meats
61
what is the source of campylobacter
- part of chicken gut flora
- 50% of campylobacter contaminates chicken carcass
62
how is campylobacter killed
by cooking
63
what's a source of campylobacter other than chicken
- rainfall caused drainage of sheep feces into a shallow aquifer
- the aquifer was not chlorinated and consumption led to thousands of campylobacteriosis illnesses
64
campylobacter incubation duration
2-11 days
65
how long does a campylobacter disease actually last
3 days to 3 weeks
66
symptoms of campylobacter diseases
- diarrhoea, sometimes bloody
- abdominal cramps
- fever
- sometimes bacteraemia (in children and immunocompromised patients)
67
describe mortality with campylobacter
- death is rare: 1 in 5-10,000 cases
- infants and the immunocompromised are mostly harmed
68
what are the post-infection sicknesses associated with campylobacter
- cross reacting antibodies
- Guillian-Barre syndrome (1 in 1000)
- reactive arthritis (1 in 100)
69
what are the factors that make campylobacter impactful
- flagella
- pili
- adhesins in the OM
- immune evasion and inflammation via LPS
- CLT and CDT toxins
70
functions of CLT and CDT toxins
- found in campylobacter
- CLT: increases water secretion
- CDT: leads to cell death
71
how to prevent campylobacter contamination
- clean surfaces and wash hands
- don't cross contaminate
- refrigerate completely
- cook to proper temperatures
72
what kind of diarrhoea does Clostridiodes difficile cause
nosocomial diarrhoea
73
what kind of antibiotic can trigger nosocomial diarrhoea
clindamycin
74
what kind of diarrhoea is expected with nosocomial diarrhoea
- explosive
- watery
- bloodless
75
what is the source of Clostridiodes difficile
it is a normal part of the gut flora and gastrointestinal tract
76
what % of the population carry Clostridiodes difficile
- 5%
- increases to 20% in a hospital setting
77
how can Clostridiodes difficile be spread
- person to person in a hospital setting
- spread feces-oral route
78
why are Clostridiodes difficile easily spread person to person
they form endospores so they can exist in environments for longer durations, giving them adequate time to infect others
79
who are the people most at risk for Clostridiodes difficile
- patients receiving antibiotics
- staying in hospitals over a week (time to become colonised)
- taking treatments that disrupt the colony flora
80
what antibiotics make it easier for Clostridiodes difficile infections
- beta lactams
- clindamycin
- fluoroquinolones (epidemic strain)
81
why does taking treatments that disrupt the colony flora make Clostridiodes difficile infections likely
they remove competition for C. difficle to grow
82
why does taking antibiotics make Clostridiodes difficile infections likely
- they reduce the numbers of major non-endospore forming anaerobes in the colon
- C. difficile is an endospore forming anaerobe so it grows to high numbers and secretes toxins
- it can be sensitive to antibiotics but because it can form endospores it still survives
83
what bacterial species produce endospores
only species of:
- bacillus
- clostridium
84
what allows Clostridiodes difficile to survive in a hospital environment
the fact that it can form endospores
85
what are endospores killed by
- heat (autoclaving)
- sporicidal chemicals
86
what are endospores *not* killed by
- heat (pasteurisation)
- antibiotics: as antibiotics typically target non-dormant cells
- oxygen: though C. difficile is an anaerobe, the endospore can survive with oxygen
87
which toxins does Clostridiodes difficile produce
- toxin A
- toxin B
88
how do toxins produced by C. difficile enter a cell
1) the toxin attaches to the surface of the colon cell
2) endocytosis is triggered and the toxin enters the cell in an endosome
3) the endosome is acidified and toxins are released
4) the toxin will affect G-protein glucosylation, causing signalling proteins like Rho to become glycosylated
5) this leads to signals that lead to the collapse of the actin skeleton
6) this disrupts the colon's mucosa
89
what happens when the colon's mucosa is disruption by C. difficile toxins
- normally, the colon secretes mucus and absorbs water
1) in the presence of toxin A, the colon's mucosal cells are rounded and die
2) this leads to a loss of integrity in the mucosal barrier through which toxin B can enter
3) toxin B affects the cells of the sub-mucosa
4) the damaged mucosal barrier becomes leaky so its contents reach the bloodstream, causing inflammation and other symptoms
5) colonal cell death can occur
6) a pseudomembrane of cell debris, mucus etc. can also form on the surface of the damaged mucosa
90
what is the final effect of toxication by C. difficile toxins
- severely inflamed colon that may need to be surgically removed
- may be fatal
91
who is tested for C. difficile infection
unformed stool is sampled from:
- patients suspected with C. difficile associated diarrhoea
- patients hopsitalised with diarrhoea for 72h+
- patients with potentially infective diarrhoea persisting 48h+ that is negative for common enteropathogens
92
what tests are done to test for C. difficile
- antibody based tests: for toxins or GDH (enzyme produced by C. diffile)
- if GDH+/toxin -, samples are put through PCR to double check for toxin genes
93
what are unideal tests for C. difficile
- gram-staining, as many people carry C. difficile unharmed
- growing in culture, however this is still done for epidemiology and identification of resistance genes
94
how are C. difficile infections treated
- discontinue implicated antibiotic
- treat with anti-C. difficile antibiotic
- support fluid loss
- pain relief
- restoration of microflora: probiotics or fecal transplant
95
examples of anti-C. difficile antibiotics
- IV (injection) metronidazole
OR
- oral vancomycin
96
what do we do for the ward if a patient has C. difficile
- attention to hygiene
- thorough cleaning where patient has been
- toilet disinfectant
- sporicidal disinfectant
- limit using the implicit antibiotic (unless necessary)
97
what is the relapse rate of C. difficile
20% - endospores can form in colon and continue to live on and begin producing toxins again
medsci 202
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