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GI Infections Flashcards

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1
Q

What symptoms characterise gastroenteritis?

A

Nausea
Vomiting
Diarrhoea
Abdominal. discomfort

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2
Q

Define diarrhoea

A

Frequent and/or fluid stool, at least 3 episodes a day

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3
Q

What is dysentery?

A

The presence of blood and pus in the stools usually accompanied with abdominal pain and fever

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4
Q

What is endocolitis?

A

Inflammation involving the mucosa of the small and large intestines

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5
Q

Which groups of people are at higher risk of viral gastroenteritis?

A

Children under five
Elderly people (especially those in nursing homes)
Immunocompromised patients

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6
Q

Give five examples of important viruses which cause gastroenteritis

A 
Norovirus
Rotavirus
Adenovirus (40 and 41)
Astrovirus
Sapovirus
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7
Q

Which viruses most commonly affects children under two, elderly people and immunocompromised people to cause gastroenteritis?

A

Rotavirus
Adenovrius
Astrovirus

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8
Q

Most viruses can’t be cultures. How then, are viruses which cause gastroenteritis detected?

A

PCR

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9
Q

Describe the structure of norovirus?

A

Non-enveloped

Single stranded RNA

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10
Q

How can norovirus be transmitted?

A

Direct person-person transmisssion via faecal-oral route or aerosolised droplets
Food/water borne transmission

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11
Q

Norovirus has a high infectious dose. T/F?

A

False- the infectious dose of norovirus is low (10-100 viridons)

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12
Q

What is the incubation period of norovirus?

A

24-48 hours

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13
Q

Norovirus can shed for up to how many weeks post-infection?

A

3 weeks

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14
Q

What are the clinical features of norovirus?

A 
Vomiting
Diarrhoea
Nausea
Abdominal cramps
Headache
Muscle aches
Fever
Dehydration
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15
Q

How long do the symptoms of norovirus last for?

A

12-60 hours

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16
Q

For how long post-infection can norovirus shed for in solid organ/bone marrow transplant patients?

A

2 years

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17
Q

How is norovirus infection treated?

A

Oral/IV fluids
Antispasmodics
Analgesics
Antipyretics

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18
Q

Antibodies are developed to norovirus but these only remain for a short period, provide no long-lasting immunity. T/F?

A

True

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19
Q

What are the infection control policies for norovirus infection?

A

Isolation and cohosting of patients
Symptomatic staff excluded until symptom free for 48 hours
Patients should not be moved
New patients should not be admitted

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20
Q

Describe the structure of rotavirus?

A

Non enveloped

Double stranded RNA virus

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21
Q

Rotavirus has a low infectious dose and is stable in the environment. T/F?

A

True

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22
Q

What is the incubation period of rotavirus?

A

1-3 days

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23
Q

How is rotavirus transmitted?

A

Mainly by the faecal-oral route or fomites

Food/water borne spread possible

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24
Q

What are the symptoms of rotavirus infection?

A

Watery diarrhoea
Abdominal pain
Vomiting
Loss of electrolytes leading to dehydration

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25
Q

For how long do the symptoms of rotavirus infection normally last?

A

3-7 days

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26
Q

What are the possible complications of rotavirus infection?

A

Severe chronic diarrhoea
Dehydration
Electrolyte imbalance
Metabolic acidosis

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27
Q

Antibodies against rotavirus are produced and this leads to immunity against further infection. T/F?

A

False - the antibodies which are produced don’t lead to permanent immunity but do lessen the severity of subsequent infection

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28
Q

A rotavirus vaccine is available. T/F?

A

True

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29
Q

Describe the structure of adenovirus?

A

Double stranded DNA virus

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30
Q

Which serotypes of adenovirus cause gastroenteritis?

A

Adenovirus 40 and 41

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31
Q

What are the symptoms fo adenovirus 40/41 infection?

A

Fever

Watery diarrhoea

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32
Q

Describe the structure fo astrovirus

A

Single stranded RNA virus

Non-enveloped

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33
Q

Astrovirus causes very severe gastroenteritis compared to other aetiologies. T/F?

A

False - astrovirus causes less severe gastroenteritis than other enteric pathogens

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34
Q

In the developed world, what mode of transmission is mainly associated with GI infection?

A

Food-borne infection

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35
Q

In the developing world, what is the biggest factor contributing to GI infection?

A

Lack fo clean water and poor sanitation

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36
Q

Give examples of the physiological barriers to infection of the GI tract.

A

Lysoyme in the mouth
Acidic pH of the stomach
Mucous/bile/secretory IgA/ lymphoid tissue/epithelial turnover/normal flora of the small intestine
Epithelial turnover/normal flora of the large intestine

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37
Q

The normal flora of the small and large intestines are mostly what type of microorganisms?

A

Anaerobes

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38
Q

Many GI infections are zoonotic. What does this mean?

A

They are transmitted to humans from animals

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39
Q

What key factors are important to establish when taking a history from a patient with GI infection?

A 
Nature of diarrhoea
Timing (acute/chronic)
Food history
Recent antibiotic usage
Foreign travel
Occupation
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40
Q

What investigations should be conducted for a patient with GI infection?

A 
FBC
U&Es
Blood film
Stool sample
Sigmoidscopy
Abdominal X-RAY/CT
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41
Q

What is an enrichment broth?

A

Contains nutrients that promote the preferential growth of the pathogen

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42
Q

What is selective culture media?

A

Suppresses the growth of background flora while allowing the growth of the pathogen

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43
Q

What is differential culture media?

A

Distinguishes mixed microorganisms on the same plate using biochemical characteristics of microorganisms growing in the presence of specific nutrients combined with an indicator which changes colour

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44
Q

What is the most important factor in the treatment of GI infection?

A

Hydration / giving the patient fluids

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45
Q

Why is antibiotic treatment generally not used for GI infection?

A

May prolong symptom duration
Exacerbate symptoms
Promote emergence of antibiotic resistance
Be harmful such as in STEC infection

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46
Q

How can GI infections be prevented?

A 
Provision of safe, clean drinking water
Proper sewage d isposal
Education in hygienic food preparation
Pasteurisation of milk and dairy products
Sensible travel food practices
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47
Q

Describe why there is such as potential for new enteric pathogens to emerge?

A

Pathogenecity traits are often grouped together in large interns of pathogenicity. These can be transferred to other organisms via bacteriophages, plasmids and transposons.
Pathogenicity traits frequently contain antibiotic resistance genes

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48
Q

Why do GI infections caused by intoxication have a short incubation time?

A

Because the preformed toxin is present in food and usually takes only a few hours for symptoms to appear.

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49
Q

What are three of the most common causes of GI infection?

A

Salmonella
Campylobacter
E.coli

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50
Q

What type of bacteria is salmonella?

A

Gram negative bacilli

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51
Q

Salmonella are non-lactose fermenters. T/F?

A

True

52
Q

How can salmonella infection be acquired?

A

Contaminated food especially pork, poultry and other meat and dairy products
Waterborne infection is less common

53
Q

There are seasonal peaks of salmonella infection in which months?

A

Summer and autumn

54
Q

How does salmonella cause diarrhoea?

A

By invading epithelial cells in the distal small intestine, causing inflammation

55
Q

What are the possible results of metastatic salmonella infection?

A

Osteomyelitis
Septic arthritis
Meningitis

56
Q

What is the incubation period of salmonella?

A

12-72 hours

57
Q

What are the symptoms of salmonella infection?

A

Watery diarrhoea
Fever
Vomiting

58
Q

In severe salmonella infections, what antibiotics may eb used?

A

Beta lactams
Quinolones
Aminoglycosides

59
Q

What type of bacteria are campylobacter?

A

Gram negative bacilli

60
Q

What is the most clinically important species of campylobacter?

A

C.jejuni

61
Q

What animals can acts as a reservoir for campylobacter?

A 
Poultry
Cattle
Sheep
Rodents
Wild birds
62
Q

In what months is there seasonal peaks of campylobacter infection?

A

May

September

63
Q

How is campylobacter transmitted?

A

Contaminated food, milk and water

64
Q

How does campylobacter infection cause diarrhoea?

A

Causes inflammation, ulceration and bleeding in the small and large intestines via bacterial invasion

65
Q

In rare cases campylobacter infection can cause post-infectious demyelinated syndrome. T/F?

A

True

66
Q

What is the incubation period of campylobacter?

A

2-5 days

67
Q

How long do the symptoms fo campylobacter infection last?

A

2-10 days

68
Q

What are the symptoms fo campylobacter?

A

Bloody diarrhoea
Cramping abdominal pain
Fever
(Vomiting not usually a feature)

69
Q

Which antibiotics can be used to treat severe or persistent campylobacter infection?

A

Clarithromycin

Erythromycin

70
Q

What type of bacteria is e.coli?

A

Gram negative bacilli

71
Q

What are the six diarrhoeagenic groups of E.coli?

A 
Enteropathogenic E.coli
Enterotoxigenic. e.coli
enterohaemorrhagic e.coli
enteroinvasive e.coli
entero-agrgegative e.coli
diffuse aggregative e.coli
72
Q

What syndrome may result form the use fo antibiotics in e.coli infection?

A

Haemolytic uraemic syndrome

73
Q

What are the symptoms of enteropathogenic e.coli infection?

A

Watery diarrhoea
Abdominal pain
Vomiting
Fever

74
Q

Describe the pathophysiology fo enteropathogenic e.coli infection?

A

Adheres via pili, forms attaching and effacing. lesion which is mediated by intimin protein
Disrupts intestinal microvilli

75
Q

What is the major bacterial cause fo diarrhoea in infants and children in the developing world?

A

Enterotoxigenic e.coli

76
Q

What are the symptoms of enterotoxigenic e.coli infection?

A

Watery diarrhoea
Abdominal pain
Vomitng
No associated fever

77
Q

What is the incubation period of enterotoxigenic e.coli?

A

1-7 days

78
Q

How long do the symptoms fo enterotoxigenic e.coli infection last for?

A

2-6 days

79
Q

How does enterotoxigenic e.coli cause diarrhoea?

A

Heat labile and heat stabile toxins which are structural and functional analogues of the cholera toxin

80
Q

What is the most common serotype of enterohaemorrhagic e.coli?

A

E.coli 0157

81
Q

What is the main mode of transmission of enterohaemorrhagic e.coli?

A

Contaminated food, water and dairy products

Direct environmental contact with animal faeces

82
Q

What toxins are produced by enterohaemorrhagic e.coli?

A

Shiga like toxins

83
Q

What is the incubation period of enterohaemorrhagic e.coli?

A

1-7 days

84
Q

How long do the symptoms fo enterohaemorrhagic e.coli infection last for?

A

5-10 days

85
Q

What are the symptoms of enterohaemorrhagic e.coli infection?

A

Bloody diarrhoea
Abdominal pain
Vomiting
No associated fever

86
Q

What is haemolytic uraemiac syndrome?

A

A triad of microangiopathic haemolytic anaemia, thrombocytopenia and acute renal failure

87
Q

What type of bacteria is shigella?

A

Gram negative bacilli

88
Q

What are the four species fo shigella?

A

Shigella sonnei
Shigella boydii
Shigella flexneri
Shigella dysenteriae

89
Q

Which. species of shigella is associated with milder infections?

A

Shigella sonnei

90
Q

Which species of shigella is associated with the most severe disease?

A

Shigella dysenteriae

91
Q

Shigella does not persist in the environment. Thus, what is the most important mode of transmission of shigella?

A

Person to person spread via the faecal-oral route

92
Q

S.dysenteriae produces a potent protein exotoxin (shiga toxin) which damages the intestinal epithelium. What other structures can this target?

A

Glomerular epithelium causing renal failure

93
Q

Infection with which organism is the most common cause of dysentery?

A

Shigella

94
Q

What are the symptoms fo shigella infection?

A

Marked, cramping abdominal pain
Dysentery
Fever
Vomiting is uncommon

95
Q

What type of bacteria is vibrio cholerae?

A

Gram negative bacilli

96
Q

In what parts of the world is vibrio cholerae endemic?

A

Southeast Asia
Africa
South America

97
Q

Vibrio cholerae has many. animal reservoirs. T/F?

A

False - it only infects humans

98
Q

How does vibrio cholerae spread?

A

Contaminated food and water

99
Q

What are the symptoms fo vibrio cholerae infection?

A

Sever, profuse water diarrhoea

Profound fluid loss and dehydration causing hypokaelamia, metabolic acidosis, hypovolaemic shock, cardiac failure

100
Q

What type fo antibiotics may shorten the duration of shedding of vibrio cholerae?

A

Tetracyclines

101
Q

S.aurerus toxins causing Gi infection are especially present in which foodstuffs?

A

Meats
Cakes
Pastries

102
Q

What are the symptoms of s.auerus toxin mediated GI infection?

A

Profuse vomiting
Abdominal cramps
No fever or diarrhoea

103
Q

What is the incubation time for s.auerus toxin mediated GI infection?

A

30 minutes

104
Q

What type of bacteria are bacillus cereus?

A

Gram positive bacilli

105
Q

What foodstuffs are typically associated with b.cereus GI infection?

A

Fried rice

106
Q

What are the symptoms of b.cereus toxin mediated emetic GI infection?

A

Profuse vomiting
Abdominal cramps
Watery diarrhoea
No fever

107
Q

What is the incubation period of b.cereus toxin mediated emetic GI infection?

A

30mins-6hours

108
Q

What are the symptoms of b.cereus toxin mediated diarrhoea GI infection?

A

Watery diarrhoea
Cramping abdominal pain
No vomiting or fever

109
Q

What is the incubation period of b.cereus toxin mediated diarrhoeal GI infection?

A

8-12 hours

110
Q

What type of bacteria is clostridium perfringens?

A

Anaerobic gram positive bacilli

111
Q

What are the symptoms of c.perfringens toxin mediated GI infection?

A

Watery diarrhoea
Abdominal cramps
No fever or vomiting

112
Q

What is the incubation period of c.perfringens toxin mediated GI infection?

A

6-24hours

113
Q

Which heat-labile protein neurotoxins of clostridium botulinum cause disease in humans?

A

Types A, B and E

114
Q

What foodstuffs is preformed botulism toxin particularly associated with?

A

Improperly processed canned foodstuffs

115
Q

What are the symptoms fo clostridium botulinum toxin mediated disease?

A

Flaccid paralysis
Progressive muscle weakness
Respiratory failure of chest/diaphragm involved

116
Q

What is used to treat clostridium botulinum toxin mediated disease?

A

Antitoxin

117
Q

Other than antibiotics, which drugs are associated with c.difficile infection?

A

Proton pump inhibitors

118
Q

What condition may result from severe c.difficile infection?

A

Pseudomembranous colitis

119
Q

In mild c.difficile infection what antibiotic is given?

A

Oral metronidazole

120
Q

In severe c.difficile infection what antibiotic is given?

A

Oral vancomycin

121
Q

What type of bacteria is listeria monocytogenes?

A

Gram positive coccobacili

122
Q

What groups of people are more likely to become infected with listeria monocytogenes?

A

Pregnant women
Elderly people
Immunocompromised individuals

123
Q

Which foodstuffs are particularly associated with listeria monocytogenes?

A 
Unpasteurised milk
Soft cheese
pate
Cooked meats
Smoked fish
Coleslaw
124
Q

What can result from severe, systemic infection with listeria monocytogenes?

A

Septicaemia

Meningitis

125
Q

Which antibiotics are used to treat listeria monocytogenes infection?

A

IV Ampicillin and gentamicin

126
Q

What is the incubation period of listeria monocytogenes?

A

3 weeks

127
Q

For how long does listeria monocytogenes infection cause symptoms?

A

1-2 weeks

Clinical Microbiology (17 decks)

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