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MD3002 > Gi bacterial and viral infections > Flashcards

Gi bacterial and viral infections Flashcards

1
Q

what damage can GI pathogens do

A 
local inflammation
ulceration 
perforation of mucosal epithelium
Disruption of normal microbiota
Pharmacological action of bacterial toxins
Invasion to blood or lymphatics
villous atrophy
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2
Q

describe types of epithelial perforation

A

Ruptured ulcer / perforated ulcer

may result in leaking of food and gastric juices to the abdominal cavities

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3
Q

what pathogens can cause diarrhoea

A

campylobacter
shigella
EPEC
cholera

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4
Q

how long can campylobacter incubate for

A

2-11 days

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5
Q

how long can diarrhoea caused by campylobacter last for

A

3 weeks

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6
Q

what symptoms may present with campylobacter or shigella

A

bloody stools

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7
Q

what does EPEC stand for

A

enteropathogenic E. coli

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8
Q

what may result from e.coli or cholera infection

A

watery stools

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9
Q

what are some bacterial diarrhoeal pathogens

A
  • Vibrio cholerae
  • Escherichia coli
  • Campylobacter jejuni
  • Salmonella spp.
  • Shigellaspp.
  • Listeria monocytogenes
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10
Q

describe V. cholerae

A
  • Gram negative
  • Comma-shaped rod
  • Flagellated

found in water

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11
Q

what is O1 antigen associated with

A

Associated with early pandemics

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12
Q

what is non O1 antigen associated with

A

recent outbreaks

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13
Q

what vaccines are available for cholera

A
  • Parenteral vaccine: low protective efficiency

* Oral vaccine: effective & suitable for travellers

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14
Q

describe the pathogenesis of V.cholerae

A
  • Only infective in large doses
  • Many organisms killed in stomach
  • Colonisation of small intestine involving flagellarmotion, mucinase, attachment to specific receptors
  • Production of multicomponent toxin
  • Loss of fluid and electrolytes without damage to enterocytes
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15
Q

what are the consequences of cholera infection

A 
Fluid loss of up to 1 litre/hour
•Electrolyte imbalance leading to dehydration, metabolic acidosis & hypokalemia
•Hypovolaemicshock
•40-60% mortality
•
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16
Q

describe E.coli

A
  • Gram negative
  • Bacillus
  • Member of normal gastrointestinal microbiota
  • Some strains possess virulence factors enabling them to cause disease
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17
Q

what are the types of E. coli

A
  • EPEC enteropathogenic
  • ETEC enterotoxigenic
  • VTEC verocytotoxin-producing
  • EHEC enterohaemorrhagic
  • EIEC enteroinvasive
  • EAEC enteroaggregative
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18
Q

what is EPEC (enteropathogenic) responsible for

A

sporadic cases and outbreaks of infection in under 5’s

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19
Q

what is ETEC (enterotoxigenic) responsible for

A

travellers’ diarrhoea

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20
Q

what is VTEC / EHEC (verocytoxin/ enterohaemorrhagic) responsible for

A

sporadic cases and outbreaks of gastroenteritis

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21
Q

what is EIEC (enteroinvasive) responsible for

A

food-borne infection in areas of poor hygiene (often persistent diarrhoea)

22
Q

where is EAEC found (enteroaggregative e. coli)

A

resource-poor countries

23
Q

describe C. jejuni

A
  • Gram negative

* Helical bacillus

24
Q

how is C. jejuni spread

A

consumption of raw / undercooked meat, contaminated milk

25
Q

what does C. jejuni cause

A

Commonest case of diarrhoea in developed world

Mucosal inflammation and fluid secretion

26
Q

what is the histological appearance of C.jejuni infection

A
  • Inflammation involves entire mucosa
  • Villous atrophy
  • Necrotic debris in crypts
  • Thickening of basement membrane
27
Q

what is Salmonella sp

A

Gram negative Bacilli

28
Q

what does Salmonella do

A

food associated diarrhoea

transmission through meat, eggs milk or human to human

29
Q

describe the pathogenesis of Salmonella

A
  • Ingestion of large numbers of bacteria
  • Absorption to epithelial cells in terminal section of small intestine
  • Penetration of cells and migration to lamina propria
  • Multiplication in lymphoid follicles
  • Inflammatory response mediates release of prostaglandins
  • Stimulation of cyclic AMP
  • Release of fluid and electrolytes causing diarrhoea
30
Q

what does S. typhi and S. paratyphi cause

A

typhoid and paratyphoid

travel around the body in macrophages

spread via faeces in contaminated water, can become a chronic carrier

31
Q

describe typhoid vaccines

A 
Oral; live attenuated
–booster after 5 years
•Parenteral; capsular polysaccharide
–Booster after 2 years
•50-80% effective
•Recommended for travellers to endemic areas
32
Q

what is shigellosis

A

shigella infection causing dysentery

faecal- oral
human only

33
Q

describe the pathogenesis of Shigella

A
  • Attaches to mucosal epithelium of distal ileum and colon
  • Causes inflammation and ulceration
  • Rarely invasive
  • Produces Shiga toxin
  • Diarrhoea watery initially, later can contain blood and mucus
  • Disease usually self-limiting
34
Q

what is L. monocytogenes

A
  • Coccobaccillus
  • Causes listeriosis
  • Food-borne pathogen associated with paté, soft cheese, unpasteurised milk

usually presents as meningitis

35
Q

who is at risk of L.monocytogenes infection

A

–Pregnant women (with possibility of infection of the baby in uteroor at birth)
–Immunosuppressed individulas(e.g. those with AIDS or on cancer / immunosuppresivedrugs)
–The elderly

36
Q

what viruses can cause diarrhoea

A
  • Rotavirus
  • Norovirus
  • Enteric Adenovirus

more rarely:
•Calicivirus
•Coronavirus
•Astrovirus

37
Q

describe rotavirus

A 
looks like a wheel
infects mammals 
commonest in very young children 
high virulence
faeco-oral or faeco-respiratory
38
Q

describe the pathogenesis of rotavirus

A
  • Incubation period of 1-2 days
  • Replication of virus in small intestinal epithelial cells at tips of villi
  • Results in villous atrophy
  • Damage caused to infected cells leaving immature cells with reduced absorptive capacity for sugar, water and electrolytes
  • Onset of vomiting, diarrhoea lasting 4 –7 days
  • Up to 1010–1011virus particles/gram faeces released
39
Q

describe the rotavirus vaccine

A 
•RotaRix; RotaTeq
–Oral administration (2-3 doses)
–First dose at 6-10 weeks of age
–Live, attenuated virus
•Introduced in UK from 2013
•In US, hospital admissions decreased by 86% since introduction
•Has already been used in >30 countries
40
Q

what is norovirus

A

•a.k.a. “winter vomiting disease”
•Accounts for most non-bacterial outbreaks worldwide
•Past infection in 60% of adults
•Human only pathogen
•Transmission is faeco-oral, contaminated water / shellfish, fomites
•

41
Q

what is enteric adenovirus

A
  • Accounts for 10% of community-acquired diarrhoeas in young children
  • No seasonal incidence
  • Asymptomatic infections common
  • Mild, but prolonged diarrhoea
42
Q

what pathogen might multiply after tetracycline treatment

A

Staphylococcus aureus& Candida sp.

43
Q

describe C. difficile

A
  • Produces spores for survival
  • Produces an enterotoxin and a cytotoxin
  • Not only associated with antibiotic use
  • Now associated with >55,000 cases in England/Wales per annum
  • More severe disease associated strain 027 which produces more enterotoxin (toxin A) than cytotoxin(toxin B)
  • Nosocomial infections largely responsible for increase in cases
44
Q

describe the appearance of Helicobacter pylori

A
  • Gram negative
  • Spiral
  • Flagellated
  • Microaerophilic
  • > 80% infected individuals are asymptomatic

can cause stomach ulcers

45
Q

what diseases can H. pylori cause

A
  • Duodenal ulcers
  • Gastric ulcers
  • Gastro-oesophageal reflux disease
  • Non-ulcer dyspepsia
46
Q

what are the Key featurs of H. pylori

A
  • Acid-inhibiting protein –survival in stomach
  • Urease –neutralisation of acid pH
  • Adhesins –binding to gastric epithelium
  • Cytotoxin –damage to gastric epithelium
  • Flagellum –movement through gastric mucus layer
47
Q

how is H. pylori treated

A 
•1 week triple combination therapy
EITHER:
Proton pump inhibitor (PPI)
& Clarithromycin
& Amoxycillin
OR:
Proton pump inhibitor (PPI)
& Clarithromycin
& Metronidazole
48
Q

what toxins can cause food poisoning

A
  • emetic toxins of Bacillus cereus
  • enterotoxin of Staphylococcus aureus
  • neurotoxin of Clostridium botulinum
49
Q

what is oral rehydration therapy

A

the replacement of fluids and electrolytes lost during diarrheal illness

contains glucose, NaCl, KCl, and other salts

50
Q

what is listeriosis

A

after eating certain foods contaminated with listeria
causes mild fever, vomiting and diarrhoea
may cause meningitis
caused by L. monocytogenes

51
Q

how long does shigella incubate for

A

1-4 days and lasts for 3 days

52
Q

what might clindamycin lead to

A

c. difficile infection

MD3002 (56 decks)

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