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Y2 Clinical Pathology > Gastrointestinal Infections 2 > Flashcards

Gastrointestinal Infections 2 Flashcards

1
Q

what organisms can cause foodborne gastroenteritis?

A
  • Staphylococcus aureus
  • Bacillus cereus
  • Clostridium perfringens
  • Clostridium botulinum
  • Escherichia coli
  • Salmonella spp.
  • Shigella spp.
  • Campylobacter spp.
  • Yersinia enterocolitica
  • Vibrio parahaemolyticus
  • Listeria monocytogenes
  • Aeromonas hydrophilia
  • Plesiomonas spp.
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2
Q

What organisms can cause non-foodborne gastroenteritis?

Where does this tend to come from?

A
  • salmonella spp.
  • campylobacter spp.
  • Escherichia coli (EHEC or VTEC 0157)

mainly associated with recreational water and animal contact, with contributory factors such as poor hand hygiene

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3
Q

What causes antibiotic-associated diarrhoea?

A

Clostridium difficile

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4
Q

What organisms cause waterborne gastroenteritis?

A
  • Giardia lamblia
  • Entamoeba histolytica
  • Cryptosporidium parvum
  • Vibrio cholerae

sporadic cases of cholera are seen in the UK in returning travellers

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5
Q

What organisms are associated with causing viral gastroenteritis?

A
  • rotaviruses
  • norwalk viruses
  • noroviruses
  • adenoviruses
  • astroviruses
  • caliciviruses
  • parvoviruses
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6
Q

What is the problem associated with C perfringens / B cereus and Staph?

A

the spores of C perfringens / B cereus can survive cooking

food poisoning can occur when food (meat) is cooked in advance and kept warm

With staphylococcus aureus, food poisioning can occur after eating food contaminated with toxin

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7
Q

What is the most common cause of bacterial gastroenteritis in England?

A

Campylobacter

this comes from undercooked meat

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8
Q

What does shigella cause?

A

bacillary dysentery

it comes from water contaminated with sewage

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9
Q

What are the main differences between intoxication and infection?

A

intoxication:

  • ingestion of a pre-formed toxin
  • rapid incubation period (minutes to hours)
  • onward transmission is not communicable

infection:

  • ingestion of bacteria, virus or parasite
  • slower incubation period (hours to days)
  • onward transmission from person to person (faecal oral)
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10
Q

What are the symptoms of intoxication and infection?

A

intoxication:

  • vomiting, nausea & diarrhoea
  • weakness
  • respiratory failure
  • numbness
  • sensory / motor dysfunction

infection:

  • diarrhoea, nausea & vomiting
  • abdominal cramps
  • fever
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11
Q

What are the factors influencing intoxication and infection?

A

intoxication:

  • inadequate cooking
  • improper handling temperatures

infection:

  • inadequate cooking
  • cross contamination
  • poor hygiene and handwashing procedures
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12
Q

What are the most common causes of foodborne gastroenteritis?

Why are they difficult to identify?

A

most common:

  • bacteriodes
  • prevotella

obligate anaerobes:

  • clostridia
  • bifidobacteria

facultative anaerobes:

  • enterobacteriacea
  • enterococci

difficult to identify pathogenic organisms from commensal flora, especially as many commensals can sometimes cause disease

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13
Q

What are common causes of foodborne gastroenteritis found in dairy, eggs and vegetables?

A

dairy:

  • Campylobacter
  • Salmonella spp.

eggs:

  • Salmonella spp.

vegetables:

  • Aeromonas spp.
  • C perfringens
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14
Q

What are common causes of foodborne gastroenteritis found in meats?

A

meats:

  • Clostridium perfringens
  • Bacillus cereus
  • Aeromonas spp.
  • Campylobacter spp.
  • Salmonella spp.

ground beef:

  • e. coli O157:H7

poultry:

  • Campylobacter spp.

pork:

  • C. perfringens
  • Yersinia enterocolitica
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15
Q

What are common causes of foodborne gastroenteritis found in seafood and oysters?

A

seafood:

  • astrovirus
  • Aeromonas spp.
  • Plesiomonas spp.
  • Vibrio spp.

oysters:

  • calcivirus
  • Plesiomonas spp.
  • Vibrio spp.
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16
Q

What are common causes of foodborne gastroenteritis in mayonnaise, rice and canned foods?

A

mayonnaise containing salads & highly processed foods:

  • Staphylococcus aureus

rice & starchy foods:

  • Bacillus cereus

canned foods & honey:

  • Clostridium botulinum
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17
Q

What symptoms does eating food contaminated with S. aureus have?

What types of products is it associated with?

A
  • heat stable enterotoxin
  • nausea and vomiting (often projectile)
  • no fever and little or no diarrhoea
  • symptoms usually 1-4 hours after ingestion
  • associated with mayonnaise, meat & dairy products
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18
Q

What are the 2 different enterotoxins formed when spores of Bacillus cereus germinate?

A
  • heat stable emetic form
  • heat labile diarrhoeal form
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19
Q

What are the symptoms of ingestion of the heat stable emetic form of Bacillus cereus spores?

What types of foods is this associated with?

A
  • vomiting
  • no fever and little or no diarrhoea
  • symptoms occur 2-6 hours after ingestion
  • associated with cooked rice and other starchy foods
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20
Q

What are the symptoms after ingestion of the heat labile diarrhoeal form of Bacillus cereus?

What foods is this associated with?

A
  • profuse diarrhoea
  • no fever and little vomiting
  • symptoms occur 10-14 hours after ingestion
  • found in a wide variety of foods
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21
Q

What are the symptoms of ingestion of the Clostridium perfringens toxin?

What foods is this associated with?

A

enterotoxin formed when the organism sporulates

  • heat labile
  • abdominal cramping and watery diarrhoea
  • no fever
  • symptoms occur 8 - 24 hours after ingestion
  • associated with meat and meat products
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22
Q

What is the toxin like associated with Clostridium botulinum?

A

neurotoxin is formed when the organism sporulates

this is a large AB toxin

the B portion protects the toxin from stomach acid

the A portion blocks neurotransmission

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23
Q

What are the symptoms associated with the ingestion of the Clostridium botulinum toxin?

What foods is this associated with?

A
  • blurred vision
  • dry mouth
  • constipation
  • abdominal pain
  • descending flaccid paralysis
  • respiratory failure
  • no fever
  • symptoms occur 1-2 days after ingestion
  • it is associated with improperly canned food
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24
Q

What is infant botulism?

What are the symptoms?

A

C. botulinum spores in honey can colonise infant (<1 year) GI tract and produce toxin

this produces constipation and neurological symptoms

it is a milder disease than in adults

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25
Q

What type of organisms cause salmonella gastroenteritis?

Why do you need a large number to infect?

Where are they found?

A
  • Gram-negative motile, facultative anaerobes
  • non-lactose fermenters (XLD, DCA, S-S agar)
  • they are killed by gastric acid so high numbers are needed to infect
  • found in the guts of chickens, reptiles, birds and humans
  • can be transferred directly from animals to humans or via food products
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26
Q

What are the symptoms of salmonella gastroenteritis?

How long do they last for?

A
  • symptoms occur 6-8 hours after contaminated food / water
  • nausea
  • abdominal cramps
  • vomiting & diarrhoea
  • may have fever, headache, myalgia
  • usually self-limiting and symptoms last 2 days - 1 week
  • antibiotic treatment is not needed
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27
Q

In which types of patients should antibiotic treatment for Salmonella gastroenteritis be given?

A

antibiotic treatment is not recommended for healthy people

  • older than 50 years of age
  • immunocompromised
  • have cardiac valve disease or endovascular abnormalities, including prosthetic vascular grafts
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28
Q

If antibiotic treatment is given in salmonella gastroenteritis, what should be given?

A

if antibiotic treatment is indicated, prescribe ciprofloxacin 500 mg twice a day for one day only

check with the microbiology lab that the isolate is sensitive

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29
Q

What is Shigella?

Why are only low numbers needed to infect?

A
  • Shigella causes dysentry
  • it is a Gram negative, non-motile, facultative anaerobe
  • non-lactose fermenters (XLD, DCA, S-S agar)
  • fairly resistant to killing by gastric acid so only low numbers are needed to infect
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30
Q

Where is shigella found and how is it transmitted?

What are the main groups?

A
  • found in the guts of humans and other primates
  • primarily transmitted by faecal-oral route
  • some produce an enterotoxin and Shiga toxin
  • main groups are S. sonnei, S. flexneri, S. dysenteriae
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31
Q

What are the symptoms of shigella ingestion?

What is the treatment and incubation period?

A
  • watery diarrhoea
  • dysentery (bloody mucoid stool)
  • abdominal pain
  • significant fluid and electrolyte loss
  • 36 - 72 hour incubation period
  • it is usually self-limiting but fluid & electrolyte replacement is given in severe cases
32
Q

When should antibiotic treatment be given for Shigella gastroenteritis?

A

antibiotic treatment is not recommended for healthy people with mild shigellosis

  • those with severe disease
  • immunocompromised
  • bloody diarrhoea
33
Q

What antibiotics should be given in shigellosis?

What should be avoided?

A

if antibiotic treatment is indicated, seek advice from the local microbiologist regarding antibiotic management

ciprofloxacin 500mg twice daily for 1 day only

( continue for 5 days if the organisms is Shigella dysenteriae)

do not prescribe antimotility drugs, such as loperamide or diphenoxylate

34
Q

What is Campylobacter?

What is it sensitive to and how does it cause damage?

A
  • Gram-negative curved slender motile microaerophile
  • fairly sensitive to environmental stress
    • e.g. heat, drying, acid
    • culture media contains charcoal and antibiotics with microaerophilic conditions
  • it adheres and invades epithelial cells and produces a heat labile toxin
35
Q

What is Campylobacter associated with?

What is the most common cause of gastroenteritis?

A

it is associated with poultry and other birds

primarily transmitted by the faecal-oral route

C. jejuni is the most common cause of gastroenteritis

36
Q

What are the symptoms associated with ingestion of Campylobacter?

What is the duration and treatment?

A
  • watery diarrhoea is the most common symptom
  • some patients may have:
    • intense abdominal pain mimicking appendicitis
    • malaise
    • myalgia
    • headache
    • vomiting
  • usually self-limiting and subsides within 7 days
  • fluid & electrolyte replacement is given if it is severe
37
Q

When should antibiotics be given to someone with gastroenteritis caused by Campylobacter?

A

antibiotic treatment is not usually necessary for people with mild symptoms

  • with severe symptoms (high fever, bloody diarrhoea, more than 8 stools per day)
  • immunocompromised
  • symptoms appear to be worsening
  • symptoms have lasted longer than 1 week
38
Q

If antibiotics are indicated in Campylobacter gastroenteritis, what should be given?

A

erythromycin:

  • 250 - 500 mg four times a day for 5-7 days
  • if it is not tolerated, consider clarithromycin or azithromycin

ciprofloxacin:

  • 500 mg twice a day for 5-7 days
  • alternative to macrolides
39
Q

What is E. coli 0157:H7 (EHEC, VTEC)?

What can it produce and what is it associated with?

A
  • Gram-negative motile, facultative bacillus
  • cannot ferment sorbitol (S-MAC agar)
  • has acquired the ability to produce Shiga-toxin
  • associated with cattle and meat
40
Q

What are the symptoms of ingestion of E. coli 0157:H7 (EHEC, VTEC)?

What should be avoided?

A
  • abdominal pain
  • watery diarrhoea followed by bloody diarrhoea
  • little / no fever
  • haemorrhagic colitis
  • 10-15% develop haemolytic uraemic syndrome
    • ​acute renal failure
    • thrombocytopenia
    • microangiopathic haemolytic anaemia
  • avoid antibiotics and antimotility agents
41
Q

What is the treatment for gastroenteritis caused by E. coli 0157 (VTEC)?

What should be avoided?

A

management is entirely supportive and there is no specific treatment

  • do not prescribe antibiotics
  • avoid antimotility drugs (such as loperamide or diphenoxylate) and opioids
  • advise against the use of NSAIDs
42
Q

When can adults with gastroenteritis caused by E coli 0157 (VTEC) go back to work?

What are the exceptions to this rule, and what must they await?

A

most adults can go back to work 48 hours after the first normal stool

if the person handles food or works with vulnerable people, they should stay off work until two further stool tests, at least 48 hours apart

43
Q

What is E. Coli O157?

What does the toxin cause?

A

it is enterohaemorrhagic, VTEC and Shiga-toxin producing

the toxin causes premature destruction of the red blood cells, which then clog the kidneys and cause haemolytic-uraemic syndrome

44
Q

What are the features of enterotoxigenic E. coli (ETEC)?

A
  • causes diarrhoea in infants
  • travellers diarrhoea
  • heat labile toxin
  • watery diarrhoea and abdominal pain
  • self-limiting
45
Q

What are the features of enteropathogenic E. coli (EPEC) infection?

A
  • diarrhoea in infants < 1 year
  • mild diarrhoea in adults
  • self-limiting
46
Q

What are the characterisitics of enteroaggregative E. coli (EAEC)?

A
  • travellers diarrhoea
  • persistent diarrhoea
  • self-limiting
47
Q

What are the characteristics of enteroinvasive E. coli (EIEC)?

A
  • similar to shigellosis
  • acquried traits of shigella spp.
  • mostly watery diarrhoea, but can progress to bloody mucoid diarrhoea
  • self-limiting
48
Q

What are 4 other common causes of bacterial gastroenteritis?

A
  • Yersinia enterocolitica
  • Listeria monocytogenes
  • Vibrio parahaemolyticus
  • Plesiomonas shigelloides
49
Q

What are the symptoms of viral gastroenteritis caused by rotavirus?

How long does it last for and who is affected?

A
  • diarrhoea, vomiting and fever
  • lasts for 5 - 7 days
  • it is the major cause of diarrhoea in young children
50
Q

What are the symptoms of viral gastroenteritis caused by adenovirus?

How long does it last for and who is affected?

A
  • diarrhoea, vomiting and fever
  • lasts for 5 - 12 days
  • mainly affects infants and young children
51
Q

What are the symptoms of viral gastroenteritis caused by norwalk/norovirus?

How long does it last for and who is affected?

A
  • acute vomiting
  • diarrhoea
  • fever
  • myalgia
  • headache
  • symptoms last for 1 - 2 days
  • affects children and adults
  • common where people are gathered together e.g. nurseries, hospitals, cruise ships
52
Q

What are the symptoms of viral gastroenteritis caused by astrovirus?

How long does it last for and who is affected?

A
  • watery diarrhoea
  • lasts for 2 - 3 days
  • mainly affects children and sometimes adults
  • common in nursing homes
53
Q

What are the symptoms of viral gastroenteritis caused by calicivirus?

How long does it last for and who is affected?

A
  • produces rotavirus like symptoms in children and norwalk-like symptoms in adults
  • in adults it is associated with shellfish
54
Q

What causes amoebic dysentery?

How is it transmitted and what are the forms?

A

caused by the parasite, Entamoeba histolytica

it has a motile trophozoite and cyst form

the cyst form is transmissable from person to person

it can be asymptomatic

55
Q

What is amoebic dysentery associated with?

A

contaminated food and water

it can cause extra-intestinal disease (liver, lung, brain)

56
Q

What are the symptoms of ingestion of Entamoeba histolytica?

What are the extra-intestinal symptoms?

A
  • it has an incubation period of 15 days pro-drome
  • abdominal pain / discomfort
  • diarrhoea (watery, mucoid, bloody)
  • nausea
  • vomiting
  • tenesmus
  • malaise

extra-intestinal symptoms:

  • liver abscess - high fever & abdominal pain
  • serology may be useful
57
Q

What causes cryptosporidiosis?

Where is it found and how is it spread?

A

caused by the parasite, Cryptosporidium parvum

  • found worldwide in a wide variety of animals, fish & reptiles
  • common water contaminant
  • person-to-person spread
  • may be an asymptomatic carrier
  • demonstrate cysts in faeces by microscopy or EIA
58
Q

What are the symptoms of cryptosporidiosis?

A
  • self-limiting watery diarrhoea (around 10 days)
  • severe chronic diarrhoea in immunocompromised lasting from months to years
59
Q

What causes giardiasis?

Where is this found, how does it cause infection and how can it be identified?

A

caused by the parasite, Giardia intestinalis

  • flagellate with trophic and cystic stage
  • demonstrate presence in faeces by EIA
  • it adheres to the microvillus epithelium
  • it is a common water contaminant
  • can be an asymptomatic carrier
60
Q

What are the symptoms of giardiasis?

What is the incubation period?

A

incubation period of 1-4 weeks

  • sudden onset
  • foul-smelling, watery diarrhoea
  • abdominal cramps
  • flatulence
  • steatorrhoea
  • chronic relapsing disease can occur, particularly in IgA deficiency or intestinal diverticula
61
Q

What is the treatment for gastroenteritis caused by Giardia intestinalis?

A

prescribe antibiotic treatment for all people with confirmed giardiasis

metronidazole is the drug of choice

  • 400 mg three times a day for 5 days or
  • 500 mg twice a day for 7-10 days or
  • 2 grams once a day for 3 days

tinidazole is an alternative to metronidazole

62
Q

What causes cholera?

What are the different types and what toxin is produced?

A

caused by Vibrio cholerae - curved Gram-negative rod

01 serotype = classical cholera

Non 01(0139) = milder disease

  • it is acid sensitive so has a high infective dose
  • cholera toxin leads to rapid fluid loss from the gut
  • it is water or food borne (esp shellfish)
  • endemic in some areas of the world
63
Q

What are the symptoms of cholera?

Why must it be treated?

A
  • abrupt watery diarrhoea - “rice water stool”
  • significant fluid loss (several litres in a few hours)
  • hypervolaemic shock
  • metabolic acidosis
  • it causes death if it is untreated
  • fluid and electrolyte replacement is needed
64
Q

What causes enteric fevers?

What happens in the body to these organisms?

A

Salmonella typhi and Salmonella paratyphi

these are only found in humans

they are sensitive to acid so have a high infective dose

engulfed by macrophages, migrate to the liver, spleen and bone marrow

65
Q

What are the symptoms of enteric fever (typhoid & paratyphoid fever) in the 1st and 2nd weeks after ingestion?

A

1st week after ingestion:

  • fever
  • headache and myalgia
  • malaise
  • anorexia
  • constipation / diarrhoea

2nd week after ingestion:

  • diarrhoea
  • splenomegaly
  • high fever
  • “rose spots” in typhoid fever

1-5% become chronically colonised in the gallbladder for up to a year following symptomatic resolution

66
Q

What is the treatment for enteric fever?

A

immediate antimicrobial treatment is given

azithromycin (5 days) is the drug of choice

  • multiple resistant - fluoroquinolone (5 days) or cefixime (7 - 14 days)
  • quinolone sensitive - azithromycin (7 days) or ceftriaxone (10-14 days)
67
Q

What % of patients are affected by antibiotic-associated diarrhoea?

What organism usually causes it and why does it happen?

A
  • develops in 30% of patients on antibiotics

Clostridium difficile is the most common infectious cause

  • Gram-positive, spore-bearing obligate anaerobe
  • antibiotics deplete the normal gut flora (high risk - 3GC, aminopenicillins, FQs)
  • C. difficile spores are the ingested, germinate and produce toxins (A&B)
68
Q

What must be present in order to prove antibiotic associated diarrhoea?

A

must demonstrate toxin (EIA, CCNA) as well as the organism (GDH, NAAT) to prove disease

69
Q

What are the symptoms of antibiotic-associated diarrhoea?

What can it lead to and what are the risk factors?

A
  • watery diarrhoea, abdominal cramps and low grade fever
  • can lead to fulminant colitis, pseudomembranous colitis, toxic megacolon and death

risk factors:

  • antimicrobial treatment
  • age > 65 years
  • prolonged hospital stay
70
Q

What is the treatment for antibiotic-associated diarrhoea?

What is the main problem associated with treatment?

A

stop antibiotic and start treatment with metronidazole, vancomycin or fidaxomicin

  • recurrence in 20-30% of cases
  • first recurrence increases likelihood of further recurrence by 50%
  • other treatments include immunoglobulin, bezlotoxumab and faecal transplants
71
Q

What is Streptococcus gallolyticus?

What is it associated with causing / playing a role in?

A

it is a Gram-positive bacillus

it causes infective endocarditis and septicaemia in the elderly

it is also strongly associated with colorectal cancer

(not a cause, but may have a role in promoting it)

72
Q

What are the 2 models on how Streptococcus gallolyticus promotes colorectal cancer?

A

Model 1:

  • a bacterium benefiting from metabolites of pre-neoplastic epithelium
  • it can secrete a bacteriocin - “gallocin” that affects commensal bacteria
  • microbial imbalance may lead to malignancy

Model 2:

  • high colonisation of S. gallolyticus induces inflammatory responses
  • this accelerates transformation from pre-malignant to malignant epithelium
73
Q

what should all patients with Streptococcus gallolyticus infection be tested for?

A

colorectal cancer

74
Q

What causes gastrointestinal tuberculosis?

How does this usually present?

A

caused by Mycobacterium tuberculosis - an acid-alcohol fast bacillus

it most commonly presents as pulmonary TB

is can present elsewhere (GI, brain, bone)

75
Q

What are the symptoms of gastrointestinal tuberculosis?

A
  • abdominal pain
  • weight loss
  • anaemia
  • tiredness
  • night sweats
76
Q

What can intestinal TB be confused with?

When should it be suspected?

A

intestinal TB is not common and can be confused with IBD, intestinal infections and malignancy

high degree of suspicion for ITB in patients from high prevalence TB countries

77
Q

What is the treatment for people with active TB without CNS involvement?

A
  • isoniazid (with pyridoxine), rifampicin, pyrazinamide and ethambutol for 2 months

then

  • isoniazid (with pyridoxine) and rifampicin for a further 4 months

treatment of TB requires prolonged therapy with multiple agents to combat resistance development

treatment regime should be modified according to drug susceptibility testing

Y2 Clinical Pathology (76 decks)

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