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MICRO - Abbie > 12. Gastrointestinal infections > Flashcards

12. Gastrointestinal infections Flashcards

1
Q

What’s the definition of gastroenteritis?

A

A rapid onset diarrhoeal illness, lasting less than 2 weeks with diarrhoea (loose and unformed stool) 3 or more times a day or at least 200g of stool, which is either viral or bacterial in aetiology

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2
Q

What is the definition of diarrhoea?

A

Loose or watery stools passed at least 3x in 24 hours which can be acute, chronic or persistent

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3
Q

What is the definition of acute diarrhoea?

A

Lasting less than 14 days often due to either viral or bacterial pathogens

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4
Q

What is the definition of persistent diarrhoea?

A

Between 14-29 days

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5
Q

What is the definition of chronic diarrhoea?

A

Lasting greater than 30 days, may be due to parasites and non-infectious aetiology (e.g. IBD) should be excluded

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6
Q

How does small bowel diarrhoea present?

A

Often watery, abdominal pain, large volume with bloating and gas. Accompanying fever and blood or inflammatory cells in the stool are rare.

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7
Q

How does large bowel diarrhoea present?

A

Small volume painful stool which occurs often with blood, mucus and inflammatory cells found in the stools and an accompanying fever

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8
Q

What are the foodborne risk factors of gastroenteritis?

A

Partially uncooked/unpasteurised

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9
Q

What are exposure related risk factors of gastroenteritis?

A

Outbreak situation (>2 cases suggestive of common food source or exposure), travel history, occupational (chefs, healthcare/antibiotics-> C diff), animals, institutions/childcare facilities

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10
Q

What are host related risk factors of gastroenteritis?

A

Young children and elderly, immunocompromised patients, men who have sex with men, anal-genital, oral-anal or digital-anal contact, haemochromatosis or haemoglobinopathy

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11
Q

What is the epidemiology of GI infections?

A

Underreported, viral gastroenteritis not reported in most countries, incidence of bacterial gastroenteritis is far less than viral gastroenteritis and varies country to country, depending on rural versus urban settings and the immunosuppressive risk factors of the individual. Most self-limiting and last <24 hrs. Developing and war-torn countries tend to experience outbreaks.

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12
Q

In gastroenteritis who are the most vulnerable groups?

A

Infants and elderly

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13
Q

What are reportable infections?

A

Campylobacter, Listeria monocytogenes, E. coli O157, Salmonella, Shigella, Norovirus

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14
Q

What are the 2 main mechanisms of disease and the other which tends to occur with fever in gastroenteritis?

A

Secretory diarrhoea, inflammatory diarrhoea and enteric fever

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15
Q

How does secretory diarrhoea present?

A

No fever/low grade fever. No WBCs in stool sample.

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16
Q

What organisms cause secretory diarrhoea?

A

Vibrio cholerae, ETEC, EAggEC, EPEC, EHEC

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17
Q

How does inflammatory diarrhoea present?

A

Fever, WBCs in stool sample (neutrophils)

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18
Q

What organisms cause inflammatory diarrhoea?

A

C jejuni, Shigella, non-typhoidal Salmonella, EIEC

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19
Q

How does enteric fever present?

A

Fever, relatively little stool changes (usually more severe infection), MONONUCLEAR CELLS

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20
Q

What organisms cause enteric fever?

A

Typhoidal Salmonella, enteropathogenic Yersinia, Brucella

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21
Q

Incubation period is key in determining causative organism. What does a very short period suggest (<1 day)?

A

More likely due to toxins

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22
Q

Incubation period is key in determining causative organism. What does a longer period suggest (>1 day)?

A

Enteric pathogens, more inflammatory

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23
Q

Incubation period is key in determining causative organism. What does a longer period incubation but lasting chronically suggest (<1 day)?

A

Some parasites, C diff

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24
Q

What is the incubation period and duration of illness for S aureus?

A

Incubation period: 1-6 hours. Duration of illness: 24-48 hours

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25
Q

What is the incubation period and duration of illness for norovirus?

A

Incubation: 24-48 hours. Duration: 48-72 hours.

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26
Q

What is the incubation period and duration of illness for Clostridium perfingens?

A

Incubation: 8-16 hours. Duration: 24-48 hours.

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27
Q

What is the incubation period and duration of illness for enteric viruses (rotavirus, enteric adenovirus, astrovirus, sapovirus)?

A

Incubation: 10-16 hours. Duration: 2-9 days.

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28
Q

What is the incubation period and duration of illness for Listeria monocytogenes?

A

Incubation: 24 hours, duration: variable

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29
Q

What is the incubation period and duration of illness for enterotoxigenic E coli?

A

Incubation: 1-3 days. Duration: 2-3 days.

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30
Q

What is the incubation period and duration of illness for nontyphoidal salmonella?

A

Incubation: 1-3 days, duration: 1-7 days

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31
Q

What is the incubation period and duration of illness for Campylobacter spp?

A

Incubation: 1-3 days, duration: 5-14 days

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32
Q

What is the incubation period and duration of illness for Shigella spp?

A

Incubation: 1-3 days, duration: 2-3 days

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33
Q

What are food risk factors for S. aureus?

A

Pre-formed toxin in unrefrigerated foods

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34
Q

What are food risk factors for norovirus?

A

Molluscs and shellfish, leafy vegetables, fruit such as melon and raspberries, sandwiches, seasonal vomiting virus

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35
Q

What are food risk factors for Clostridium perfingens?

A

Meat, poultry, canned foods

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36
Q

What are food risk factors for enteric viruses?

A

Faecally contaminated food or water

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37
Q

What are food risk factors for Listeria monocytogenes?

A

Processed/delicatessen meats, hot dogs, soft cheese, pates, and fruit

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38
Q

What are food risk factors for enterotoxigenic E coli?

A

Faecally contaminated food or water

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39
Q

What are risk factors for nontyphoidal Salmonella?

A

Poultry, eggs, egg products, fresh produce, meat, fish, unpasteurised milk or juice

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40
Q

What are food risk factors for Campylobacter spp?

A

Poultry, meat, unpasteurised milk

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41
Q

What are food risk factors for Shigella spp?

A

Raw vegetables, MSM activity

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42
Q

What type of diarrhoea is seen in S aureus?

A

Watery diarrhoea with fever

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43
Q

What type of diarrhoea is seen in norovirus?

A

Watery diarrhoea

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44
Q

What type of diarrhoea is seen in Clostridium perfringens?

A

Watery diarrhoea

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45
Q

What type of diarrhoea is seen in enteric viruses?

A

Watery diarrhoea

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46
Q

What type of diarrhoea is seen in Listeria monocytogenes?

A

Watery diarrhoea

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47
Q

What type of diarrhoea is seen in enterotoxigenic E coli?

A

Watery diarrhoea

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48
Q

What type of diarrhoea is seen in nontyphoidal salmonella?

A

Inflammatory diarrhoea with fever, mucus or bloody stools

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49
Q

What type of diarrhoea is seen in Campylobacter spp?

A

Inflammatory diarrhoea with fever, mucus or bloody stools

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50
Q

What type of diarrhoea is seen in Shigella spp?

A

Inflammatory diarrhoea with fever, mucus or bloody stools

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51
Q

What is the incubation period and duration of illness for Vibrio parahaemolyticus?

A

Incubation: 1-3 days, duration: 3 days

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52
Q

What is the incubation period and duration of illness for Enterohemorrhagic E coli?

A

Incubation: 1-8 days, duration: 1 week

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53
Q

What is the incubation period and duration of illness for Yersinia spp?

A

Incubation: 4-6 days, duration: 1-3 weeks

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54
Q

What is the incubation period and duration of illness for Giardia lamblia?

A

Incubation: 7-14 days, duration: days to weeks

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55
Q

What is the incubation period and duration of illness for Cyclospora cayetensis?

A

Incubation: 1-11 days, duration: may remit and relapse over a few weeks

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56
Q

What is the incubation period and duration of illness for Cryptosporidium parvum?

A

Incubation: 2-28 days, duration: may remit and relapse over a few weeks

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57
Q

What is the incubation period and duration of illness for C difficile?

A

Incubation: N/A, duration: varies but can be up to 10-14 days or longer

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58
Q

What are food risk factors for Vibrio parahaemolyticus?

A

Raw seafood and shellfish

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59
Q

What are food risk factors for Enterohemorrhagic E coli?

A

Ground beef and other meat, fresh produce, unpasteurised milk and juice

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60
Q

What are food risk factors for Yersinia spp?

A

Pork or pork products, untreated water

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61
Q

What are food risk factors for Giardia lamblia?

A

Fecally contaminated food or water

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62
Q

What are food risk factors for Cyclospora cayetanensis?

A

Herbs and berries

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63
Q

What are food risk factors for Cryptosporidium parvum?

A

Vegetables, fruit, unpasteurised milk

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64
Q

What are food risk factors for Clostridium difficile?

A

Antibiotic associated colitis, proton pump inhibitors

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65
Q

How does diarrhoea present in Vibrio haemolyticus?

A

Inflammatory diarrhoea with fever, mucus, or bloody stools

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66
Q

How does diarrhoea present in Enterohemorrhagic E coli?

A

Inflammatory diarrhoea with fever, mucous or bloody stools

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67
Q

How does diarrhoea present in Yersinia spp.?

A

Inflammatory diarrhoea, fever, mucous, or bloody stools

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68
Q

How does diarrhoea present in Giardia lamblia?

A

Watery diarrhoea

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69
Q

How does diarrhoea present in Cyclospora cayetanensis?

A

Watery diarrhoea

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70
Q

How does diarrhoea present in Cryptosporidium parvum?

A

Watery diarrhoea

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71
Q

How does diarrhoea present in Clostridium difficile?

A

Watery or inflammatory diarrhoea with fever, mucous, or bloody stools

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72
Q

What is the mechanism of disease in secretory diarrhoea and give an example?

A

TOXIN production. Cholera toxin = classic example.
- Causes massive efflux of water and Cl-

  • cAMP will open chloride channels in the apical membrane of enterocytes
  • The toxin will form a subunit that opens up the chloride channels leading to chloride efflux into the lumen and loss of water and electrolytes
  • Leads to shock due to fluid loss
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73
Q

How do superantigens work in secretory diarrhoea?

A
  • These also act very
    quickly to cause secretory
    diarrhoea
  • Toxin superantigens bind to the T cell receptor and
    you get a massive
    cytokine release
  • The binding occurs
    outside the antigen
    binding site
  • This leads to systemic
    toxicity E.g. S aureus – mediated by superantigens
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74
Q

What plays a role in how inflammatory diarrhoea and enteric fever present??

A

If you have a bacteria, in an immunocompetent person you may get bacteraemia but
septic shock and neutrophilia unlikely -> in an immunocompromised host, you can get a large cytokine, IFN, TNF-A, IL response with potential for septic shock. Hence, clinical picture can vary with same microorganism depending on host.

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75
Q

What is the difference between inflammatory diarrhoea and enteric fever?

A

Inflammatory diarrhoea is exudative. Enteric fever is characterised by interstitial inflammation.

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76
Q

How is gastroenteritis diagnosed?

A

Stool sample and culture (including PCR). For enteric fever, blood, stool, bone marrow, duodenal fluid and urine can also be tested. Stool microscopy and culture where enteric infection suspected.

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77
Q

Why are 3 stool samples needed for ova cyst and parasites?

A

They cause intermittent shedding

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78
Q

If there is a suspicion of an outbreak what should you do?

A

Stools for bacterial, viral and parasitic infection should be tested irrespective of
blood in the stool, inflammatory markers or
presence of fever or systemic symptoms if
there is suspicion of an outbreak and if tested
with molecular methodology, should be
followed by culture for public

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79
Q

Which pathogens cause persistent or chronic diarrhoea?

A

Cryptosporidium spp, Giardia lamblia, Cyclospora cayetanensis, Cystoisospora belli, and Entamoeba histolytica

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80
Q

Which pathogens cause bloody stools?

A

STEC, Shigella, Salmonella, Campylobacter, Entamoeba histolytica, noncholera Vibrio species, Yersinia, Balantidium coli, Plesiomonas

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81
Q

Which pathogens cause fever?

A

Viral, bacterial, and parasitic infections, High temp suggestive of Salmonella or E histolytica

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82
Q

Which pathogens cause abdominal pain?

A

STEC, Salmonella, Shigella, Campylobacter, Yersinia, noncholera Vibrio species, C difficile

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83
Q

Which pathogens cause persistent abdominal pain and fever?

A

Y enterocoliticia and Y pseudotuberculosis, may mimic appendicitis

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84
Q

Which pathogens cause nausea and vomiting lasting <= 24 hours?

A

S aureus enterotoxin, or Bacillus cereus

85
Q

Vomiting and non-bloody diarrhoea 2-3 days or less pathogen?

A

Norovirus (low-grade fever in first 24 hours in 40% of infections)

86
Q

Which pathogens cause diarrhoea and abdominal cramping lasting 1-2 days?

A

Clostridium perfringens or B cereus (long incubation emetic syndrome)

87
Q

Extra-intestinal manifestations of Salmonella and Yersinia

A

Aortitis, osteomyelitis and deep tissue infection e.g. abscess

88
Q

Extra-intestinal manifestations of campylobacteria and yersinia?

A

haemolytic anaemia

89
Q

Extra-intestinal manifestations of Shigella, Campylobacteria and Yersinia?

A

Glomerulonephritis

90
Q

Extra-intestinal manifestations of STEC, Shigella dysenteriae serotype 1?

A

HUS

91
Q

Extra-intestinal manifestation of Yersinia, Campylobacteria, Salmonella and Shigella?

A

Erythema nodosum

92
Q

Extra-intestinal manifestations of Salmonella, Shigella, Campylobacteria, Yersinia, rarely Giargia and Cyclospora cayetanesis?

A

Reactive arthritis

93
Q

Extra-intestinal manifestations of Listeria and Salmonella (infants under 3 months of age are at high risk)

A

Meningitis

94
Q

S aureus and food poisoning - what proportion of the population are chronic carriers and transient carriers?

A

1/3 of the population are chronic carriers and 1/3 are transient carriers

95
Q

Explain what the organism S aureus looks like and its properties?

A

Catalase and coagulase positive, Gram-positive coccus. Appears in tetrads or clusters on Gram-stain. Yellow/golden colonies on blood agar

96
Q

How does S aureus cause food poisoning?

A

It is toxin-mediated. It produces enterotoxin which is an exotoxin that can act as a superantigen in the GI tract, releasing IL1 and IL2. Causes prominent vomiting and watery, non-bloody diarrhoea. It does NOT need to be treated because it is self-limiting.

97
Q

What is a classic situation causing Bacillus Cereus formation?

A

lassic situation: spores germinate in reheated fried rice E.g. Chinese fried rice – a recipe often used for school

98
Q

Describe the properties of Bacillus Cereus

A

Gram positive rods: spore forming

99
Q

How does Bacillus cereus cause food poisoning?

A

Bacillus cereusis a common cause of food poisoning. It generates a heat stable emetic toxin which is NOT destroyed by reheating. It also generates a heat labile diarrhoeal toxin which may be spared if food is not heated to a high enough temperature.

100
Q

How does diarrhoea and symptoms present in Bacillus cereus infection?

A

It causes watery, non-bloody diarrhoea that is self-limiting usually. Rare cause of bacteraemia in vulnerable population. Can cause cerebral abscesses. A few years ago it entered baby milk -> affected neonates and caused deaths

101
Q

Describe the properties of Clostridia

A

Gram-positive anaerobe

102
Q

What causes Clostridia and what is its source?

A

Clostridium botulinum - causes botulism. Source: canned or vacuum-packed food (honey/infants). Highly associated with honey being given to <1 yr olds -> unable to protect themselves from the preformed toxin

103
Q

How does Clostridia cause botulinism?

A

Causes disease due to ingestion of a preformed toxin(inactivated by cooking). Blocks acetylcholine release from peripheral nerve synapses

104
Q

How does botulism present?

A

Presents with paralysis

105
Q

How is botulism treated?

A

Antitoxin

106
Q

What is the source of Clostridium perfringens?

A

Reheated food (meat)

107
Q

How does Clostridium perfringens cause food poisoning?

A

Generates a superantigen which mainly affects the normal flora of colon and not the small bowel

108
Q

What is the incubation period for Clostridium perfringens?

A

8-16 hours

109
Q

How does Clostridium perfringens present and what do prolonged symptoms suggest?

A

Causes watery diarrhoea, cramps, little vomiting lasting 24 hours. Prolonged symptoms may be suggestive of gut infarction and necrosis

110
Q

What is the management for Clostridium perfringens?

A

Can be self limiting – but may also cause severe disease requiring part of bowel to be removed, associated with mortality

111
Q

What does C difficile cause and what is it often caused by?

A

It causes Pseudomembranous colitis. It is considered to be a hospital-acquired infection that is related to antibiotic treatment.

112
Q

How does C difficile cause pseudomembranous colitis?

A

It is not an invasive disease and non-toxin produced strains do not often cause disease but can colonise the gut and asymptomatic shedders of spores can continue to act as a reservoir for infection.

113
Q

What does C diff produce?

A

Toxin A (an enterotoxin) and Toxin B (cytotoxin). Toxin A causes inflammation with intestinal fluid secretion and damage to the mucosa (causes inflammatory response). Toxin B more potent than A, acts as a virulence factor

114
Q

What results may come back from the lab in a C diff sample and what do they mean?

A

When you send off a sample to lab, often return as C diff PCR +ve, toxin positive/negative – then will say which toxin present.

If PCR +ve, toxin -ve, they are still an infection risk as they may be spreading spores into environment but they may not need treating (depending on symptomatic or not).

If PCR +ve, toxin +ve -> worse

115
Q

How common is C difficile in hospital and community?

A

Uncommon in community (3%), common in hospitalised patients (30%)

116
Q

What are the main antibiotics implicated in C difficile?

A

3 Cs: Cephalosporins, Ciprofloxacin, Clindamycin

117
Q

Who tends to have C difficile?

A

A lot of children and elderly tend to asymptomatically carry this in their gut. 30% of hospitalised patients will have C. difficile. Major issue for infection control, they need to be put in a separate room.

118
Q

What is the treatment for C difficile?

A

Vancomycin PO. Metronidazole no longer used and stop antibiotics where possible.

119
Q

Who is particularly vulnerable to Listeria monocytogenes?

A

Pregnant women. Vulnerable groups include: Perinatal infection – mother may be asymptomatic but can affect fetus and cause stillbirth, and immunocompromised – these patients often have a separate menu in hospital

120
Q

What are the properties of Listeria monocytogenes?

A

It tends to occur as outbreaks of febrile gastroenteritis. Beta-haemolytic, aesculin positive with tumbling mobility

121
Q

What is the source of Listeria monocytogenes?

A

Source: refrigerated food (cold enhancement) (e.g. unpasteurised dairy, vegetables). Grows at around 4 degrees.

122
Q

How does L monocytogenes present?

A

Presents with watery diarrhoea, cramps, headache, fever and a little vomiting

123
Q

What is the treatment for Listeria monocytogenes?

A

Amoxicillin

124
Q

What are properties of enterobacteriacae?

A

Facultative anaerobes, glucose/lactose fermenters (LF), Oxidase-negative

125
Q

What is the cause of enterobacteriacae Escherichia coli?

A

Traveller’s diarrhoea, source: food/water contaminated by human faeces

126
Q

How do enterotoxins cause disease in enterobacteriacae Escherichia coli?

A

Heat labile stimulates adenyl cyclase and cAMP. Heat stable stimulates guanylyl cyclase. Acts on the jejunum and ileum, but not the colon

127
Q

Which type of Enteriobacteriacae is toxigenic and main cause of traveller’s diarrhoea?

A

Enterotoxigenic E coli (ETEC)

128
Q

Which type of Enteriobacteriacae is pathogenic, infantile diarrhoea?

A

Enteropathogenic E coli (EPEC)

129
Q

Which type of Enteriobacteriacae is invasive and causes dysentery?

A

Enteroinvasive E coli (EIEC)

130
Q

Which type of Enteriobacteriacae is haemorrhagic?

A

Enterohemorrhagic E coli (EHEC)

131
Q

What is Enterohemorrhagic E coli (EHEC) caused by and what is it also called?

A

Caused by E. coli O157:H7. Also called Shiga-toxin producing E coli or STEC.

132
Q

What does EHEC shiga-like verocytotoxin cause?

A

HUS

133
Q

What should you avoid in Enterobacteriacae?

A

AVOID ANTIBIOTICS

134
Q

What organism is non-lactose fermenting and hydrogen sulphide producing (forms black colonies)?

A

Salmonellae

135
Q

What does Salmonellae grow on?

A

Grows on TSI agar and XLD agar, selenite F broth

136
Q

What are antigens in Salmonellae

A

Cell wall O (groups A-I); Flagellar H; Capsular Vi (virulence, antiphagocytic); NOTE: the differences in these antigens helps identify the type of Salmonallae

137
Q

What are the key species of Salmonella?

A

Salmonella typhi (andparatyphi); Salmonella enteritidis; Salmonella choleraesuis

138
Q

How is Salmonella transmitted?

A

Salmonella is classically transmitted via infected meat products but it can be carried by pets, mainly reptiles (e.g. pet turtle, pet snake). This can lead to recurrent infections.

139
Q

How does Salmonella enteritidis present?

A

Enterocolitis(loose stools, diarrhoea); transmitted from poultry, eggs and meat; invasion of epithelial and subepithelial tissue of the small and large bowel; bacteraemia is infrequent<5%; high carriage rate; diarrhoea resolves in 4-7 days with abdominal pain; nausea, vomiting and fever usually resolves in 48-72 hours; NOT bloody diarrhoea

140
Q

What is the treatment for Salmonella enteritidis?

A

Usually NO treatment is needed: usually self-limiting for immune-competent patients aged 12-50 yrs where risks of antibiotic therapy and potentially prolonging carriage outweigh the benefit. In immunocompromised, may require treatment – must look at risk/benefit of treatment. Stools are positive.

141
Q

How does Salmonella typhi present? What are its extra-intestinal manifestations?

A

Typhoid (enteric) fever; transmitted only by humans; multiplies in Peyer’s patches; spreads via the endoreticular system; bacteraemia can occur; 3% are carriers(low); NOTE: sickle cell patients are at increased risk of Salmonella bacteraemia; slow onset, fever and constipation. Extra-intestinal manifestations: May cause splenomegaly and rose spots; anaemia and leucopaenia; bradycardia, haemorrhage and perforation.

142
Q

What percentage of blood and stool cultures are positive with Salmonella typhi infection?

A

Blood cultures are positive in 40-80% patients. Stool culture positivity 30-40%. (Bone marrow may have additional yield >90%)

143
Q

If someone has taken OTC antibiotics must symptoms have not resolved, present to dr at week 3 of symptoms, cultures negative, then it is worth doing bone marrow. Why?

A

bone marrow as yield here is particularly high (can be >90%) and will still be positive after some antibiotics

144
Q

What is the Tx for Salmonella typhi?

A

Ceftriaxone

145
Q

Describe the properties of Shigella:

A

Non-lactose fermenters; does NOT produce hydrogen sulphide (salmonella does); non-motile

146
Q

What antigens do Shigellae have?

A

Cell wall O antigens, Polysaccharide (groups A-D) which help identify species (i.e. Shigella sonnei, Shigella dysenteriae, Shigella flexneri(MSM))

147
Q

What is the MOST EFFECTIVE bacterial enteric pathogen (infective dose = 10-100)?

A

Shigellae

148
Q

How does Shigellae cause disease?

A

Can cause dysentery (infection of the intestines resulting in severe diarrhoea with the presence of blood and mucus in the faeces). Invading cells of mucosa of the distal ileum and colon. Producing enterotoxin (Shiga toxin). No animal reservoir (human-human transmission). No carrier state.

149
Q

What are 4 symptoms of Shigellae (and percentage of patients who experience them)?

A

Abdominal pain 70-93%; Watery diarrhoea 30-40% which proceeds to bloody diarrhoea 35-55%; Vomiting 35%; Fever 30-40%

150
Q

What is the treatment for Shigellae?

A

Disease is self-limiting to about seven days – antibiotic choice should be based on patient demographics and likely local resistance profile. Antibiotics not usually recommended, only really when trying to prevent transmission

151
Q

What are the properties of Vibrios?

A

Curved, comma-shaped, Late lactose-fermenters, Oxidase positive

152
Q

What are 3 key subtypes to worry about?

A

Vibrio cholerae, Vibrio parahaemolyticus, Vibrio vulnificus?

153
Q

What does Vibrio cholerae cause and what are the groups?

A

Causes cholera. O1 Group: epidemics, biotypes El Tor and Cholerae and serotypes Ogawa, Inaba and Hikojima. Non-O1 Group: sporadic and non-pathogens

154
Q

How is Vibrio cholerae transmitted?

A

Transmitted by contamination of water and food by human faeces (shellfish, oysters, shrimp)

155
Q

How does Vibrio cholerae cause disease?

A

Colonisation of the small bowel and secretion of enterotoxin with A and B subunits, causing persistent stimulation of adenylate cyclase.

156
Q

How does Vibrio cholerae present?

A

Causes MASSIVE DIARRHOEA (rice water stool) without inflammatory cells

157
Q

How do you treat Vibrio cholerae?

A

Treat the losses (electrolytes and fluid)

158
Q

What causes Vibrio parahaemolyticus?

A

Caused by ingestion of raw or undercooked seafood (e.g. Oysters). Major cause of diarrhoea in Japan, or when cruising in Caribbean

159
Q

How is Vibrio haemolyticus treated?

A

Self-limiting for 3 days

160
Q

What does Vibrio parahaemolyticus grow on?

A

Grows on salty agar (8.5% NaCl)

161
Q

What causes Vibrio vulnificus?

A

This is picked up by scuba divers, snorkellers etc by cutting themselves on coral, as it grows in salt-based environment

162
Q

What symptoms does Vibrio vulnificus cause and in who?

A
  • Can cause diarrhoea but has been isolated from the blood and tissues of septic patients (especially those with liver disease).
  • Causes cellulitis in shellfish handlers– often occupational
  • Can cause FATAL SEPTICAEMIA with diarrhoea and vomiting in HIV patients
163
Q

What is the treatment for Vibrio vulnificans?

A

Doxycycline

164
Q

What are the properties of Campylobacter?

A

Curved, comma or S-shaped, microaerophilic (does not require much oxygen), Campylobacter jejuni grows at 42 degrees, oxidase positive, motile

165
Q

What is the treatment for Campylobacter?

A

Self-limiting but symptoms can last for weeks. Only treat if immunocompromised (using macrolides e.g. azithromycin)

166
Q

How is Campylobacter transmitted?

A

Transmitted via contaminated food and water with animal faeces (poultry, meat and unpasteurised milk)

167
Q

How does Campylobacter cause disease?

A

Enterotoxin (leading to watery diarrhoea), can rarely get a bacteraemia

168
Q

What is the presentation of Campylobacter infection?

A

Watery, foul-smelling diarrhoea, bloody stools, fever and severe abdominal pain. Loose stools occur more than 10x a day and become bloody from 2nd/3rd day onwards in 15% of patients who may have a Campylobacter organism with the plasmid PVir which correlates with more severe disease. Diarrhoea is often self-limiting and lasts for mean of 7 days

169
Q

How is Campylobacter treated?

A

Self-limintg, lasts for an average of 7 days. Only treat if immunocompromised -> macrolide. Treatment: with erythromycin or ciprofloxacin if it hasn’t resolved in the first 4-5 days. However, by the time you get the results back, most people have self-resolved.

170
Q

What are complications of Campylobacter?

A

Guillain-Barre syndrome. Reactive arthritis.

171
Q

What are the properties of Yersinia enterocolitica?

A

Non-lactose fermenter, prefers 4 degrees (cold enrichment)

172
Q

How is Yersinia transmitted?

A

Transmitted via food that is contaminated by excrements from domestic animals (e.g. farms)

173
Q

What does Yersinia enterocolitica cause?

A

Can cause enterocolitis or mesenteric adenitis

174
Q

What conditions is Yersinia associated with?

A

Reactive arthritis and Reiter’s syndrome

175
Q

What are key types of Mycobacteria?

A

Mycobacterium avium intracellulare and Mycobacterium tuberculosis

176
Q

What is a property of Mycobacteria?

A

Will appear as Gram-variable

177
Q

Name examples of protozoa?

A

Entamoeba histolytica, Giardia lamblia, Cryptosporidium parvum

178
Q

What are properties of Entamoeba histolytica?

A

Motile trophozoite in diarrhoeal illness; non-motile cyst in non-diarrhoeal illness; killed by boiling and removed by water filters; FOUR nuclei; NO animal reservoir

179
Q

What is the pathophysiology of Entamoeba histolytica?

A

Ingestion of cysts; trophozoites move into the ileum; they colonise the caecum and colon; causes flask-shaped ulcers

180
Q

What is the presentation of Entamoeba histolytica?

A

Dysentery, flatulence, tenesmus, chronic infection: weight loss with or without diarrhoea, liver abscess

181
Q

How is Entamoeba histolytica diagnosed?

A

Stool microbiology (wet mount, iodine, and trichrome); serology in invasive disease

182
Q

What is the treatment for Entamoeba histolytica?

A

Metronidazole (for abscess) + paromomycin (for luminal disease)

183
Q

What are the properties of Giardia lamblia?

A

Pear-shaped trophozoites; TWO nuclei; FOUR flagellae; and a suction disk

184
Q

How is Giardia lamblia transmitted?

A

Transmitted by ingestion of cyst from faecally contaminated water or food. Often seen in cruise/resort settings

185
Q

How does Giardia lamblia cause disease?

A

Excystation in the duodenum is followed by trophozoite attachment; do NOT tend to get invasion; results in malabsorption of protein and fat

186
Q

What does Giardia lamblia tend to affect?

A

Travellers, hikers, day care (e.g. residential homes), mental hospitals, MSM

187
Q

How does Giardia lamblia present?

A

Foul-smelling diarrhoea, non-bloody, cramps, flatulence, NO fever

188
Q

How is Giardia lamblia diagnosed?

A

Stool microscopy, ELISA, String test

189
Q

How does the String test work?

A

Swallow a capsule containing some string - one end of the string is attached to your cheek then the rest of it will be released as the capsule dissolves in the stomach and small intestine. It will pick up various protozoal particles and eventually be pulled up out of the mouth and send to the lab

190
Q

What is the treatment for Giardia lamblia?

A

Metronidazole

191
Q

What are the properties of rotavirus?

A

dsRNA virus, wheel-like

192
Q

What is the mean duration of symptoms of rotavirus?

A

Mean duration of symptoms for 3-8 days

193
Q

Who does rotavirus tend to occur in and when in the year?

A

Occurs in children aged 6 months to 2 years. Can occasionally cause diarrhoea in the elderly. Often year round in tropical climates and in winter months in temperate areas

194
Q

How does rotavirus cause symptoms?

A

Replicates in the mucosa of small intestine

195
Q

What are the symptoms of rotavirus?

A

Secretory diarrhoea with NO inflammation; watery diarrhoea with stimulation of the enteric nervous system; vomiting is less of a prominent feature than in norovirus although it can be difficult to distinguish between them. (Huge economic burden worldwide)

196
Q

How does immunity to rotavirus develop?

A

By age 6, most children worldwide have antibodies to at least 1 type. Exposure to natural infection twice will confer life-long immunity.

197
Q

Which types of adenovirus non-bloody diarrhoea in <2 years old?

A

Types 40 + 41 can cause non-bloody diarrhoea in < 2 years old. Any type can cause illness inimmunocompromised patients

198
Q

How is adenovirus diagnosed?

A

Stool electron microscopy, antigen detection, PCR

199
Q

What are methods of infection prevention and control?

A

Targets for promotion: Breastfeeding, improved weaning practices; Clean water for drinking; Safe disposal of stools of young children; Precautions when travelling; Food handling; Public health notification; Isolates and PPE – anyone admitted with D&V; Good handwashing (VERY IMPORTANT)

200
Q

What type of vaccine is given for cholera?

A

It is an inactivated whole-cell vaccine containing serogroups O1 (Inaba, Ogawa, biotypes El Tor and classical) and O139, plus B subunit of toxin (PO). There is also a live attenuated vaccine (PO) (not recommended)

201
Q

Who is the Campylobacter vaccine given to?

A

Military, infants, travellers

202
Q

What vaccine is available for enterotoxigenic E. coli (ETEC)?

A

Inactivated and live vaccines are in trials

203
Q

What vaccines are there for Salmonella typhi?

A

Vi capsular PS (IM) and live-attenuated (PO)

204
Q

What type of vaccine is Rotarix?

A

Live-attenuated, human strain-monovalent vaccine for rotavirus - 2 x PO doses

205
Q

What type of vaccine is Rotateq?

A

Pentavalent, 1 bovine + 4 human strains for rotavirus - 3 x PO doses

206
Q

Who is Rotashield given to?

A

Used in individuals where there are concerns about intussusception.

207
Q

What is the age of vaccine for rotavirus?

A

6-12 weeks

208
Q

What types of gastroenteritis are notifiable? And which are particularly important organisms?

A

All forms of gastroenteritis are notifiable. Each trust should notify the local Health Protection Unit (HPU) to help identify outbreaks. Important organisms for gastroenteritis: Campylobacter, Clostridium spp, Listeria monocytogenes, Vibrio, Yersinia.

209
Q

What happens if an outbreak is suspected?

A

Environmental Health Officers may inspect the premises and take samples from the environment and food

MICRO - Abbie (19 decks)

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