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Infection > Lecture 6.1: Infectious Diseases of the GI > Flashcards

Lecture 6.1: Infectious Diseases of the GI Flashcards

1
Q

What is Infection?

A

The process whereby a pathogenic organism invades and multiplies in or on host tissue

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2
Q

Transmission Routes of Infection

A
  • Endogenous Infection
  • Air-borne Spread
  • Faeco-oral Spread
  • Vector Borne
  • Direct Person to Person
  • Indirect Person to Person
  • Direct Inoculation (e.g bite)
  • Consumption of Infected Material
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3
Q

Pathogenic Mechanisms: Epithelial Attachment

A
  • Attach via adhesion molecules (adhesins) of either pili or fimbrae
  • Some bacteria have the ability to produce a protective slime
  • Specific organs e.g. buccal plates of hookworms
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4
Q

Pathogenic Mechanisms: Colonization and Invasion

A
  • May travel to intracellular locations
  • May remain extracellular
  • May enter blood/lymph circulations
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5
Q

Pathogenic Mechanisms: Tissue Dysfunction

A

• Cell lysis
• Production of toxins
• Endotoxins = cell wall compounds of G-ve bacteria which generate an
inflammatory response in the host
• Exotoxin = secreted proteins (act both locally and at a distance)

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6
Q

What is Gastroenteritis?

A

Irritation/inflammation of the stomach resulting in cramping pain, nausea and
vomiting and diarrhoea

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7
Q

What is Diarrhoea?

A

Abnormal faecal discharge characterised by frequent and/or fluid stool >3/day)

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8
Q

Bristol Stool Chart: Type 1

A
  • Separate Hard Lumps

* Very Constipated

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9
Q

Bristol Stool Chart: Type 2

A
  • Lumpy and Sausage-like

* Slightly Constipated

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10
Q

Bristol Stool Chart: Type 3

A
  • Sausage shape with cracks on surface

* Normal

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11
Q

Bristol Stool Chart: Type 4

A
  • Like a smooth sausage/ snake

* Normal

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12
Q

Bristol Stool Chart: Type 5

A
  • Soft blobs with clear-cut edges

* Lacking fibre

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13
Q

Bristol Stool Chart: Type 6

A
  • Mushy consistency with ragged edges
  • Inflammation
  • Diarrhoea
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14
Q

Bristol Stool Chart: Type 7

A
  • Liquid with no solids
  • Inflammation
  • Diarrhoea
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15
Q

What are the 4 Groups of Viruses associated with Gastroenteritis?

A
  • Rotaviruses (groups A, B and C)
  • Enteric Adenoviruses (types 40 and 41)
  • Calici Viruses (noroviruses, sapoviruses)
  • Astroviruses
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16
Q

Rotavirus

A

• Major cause of infantile gastroenteritis worldwide (>200K deaths in children
<5)
• Asymptomatic infections are common (more so in breast-fed babies)

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17
Q

How can Rotavirus Infections be detected? (2)

A
  • Infection can be established via genome amplification

* ELISA for detection in faeces

18
Q

What are the 3 different ways diarrhoea is caused?

A
  • Mucosal adherence
  • Mucosal invasion
  • Production of toxins
19
Q

What are the 2 syndromes Bacterial Gastroenteritis can be divided into?

A
  • Watery diarrhoea (toxins or adherence)

* Dysentery (mucosal invasion and damage)

20
Q

What is the Salmonella Bacteria?

A

Salmonella is a genus of rod-shaped Gram-negative bacteria of the family Enterobacteriaceae

21
Q

What is a Salmonella Infection caused by?

A

Salmonella infection is usually caused by eating raw or undercooked meat, poultry, and eggs or egg products or by drinking unpasteurized milk

22
Q

Symptoms of Salmonella

A
  • Symptoms commence 12-48 hours after infection
  • Nausea
  • Cramping
  • Diarrhoea (watery->bloody)
  • Fever
23
Q

How often does Bacteraemia occur in Salmonella?

A

May occur in 1-4% of cases

24
Q

How to diagnose Salmonella?

A

Specific diagnosis from culture of the organism from faeces or blood

25
Q

What is Food Poisoning?

A

Any disease of an infective or toxic nature caused by or thought to be caused by the consumption of food and water

26
Q

What are Helminthic Infections? Where are they most common?

A
  • Infections caused by different species of parasitic worms

* Common in developing countries (affects humans & domestic animals)

27
Q

What are the most common Helminthic Infections?

A
  • Nematodes (Roundworms)- have mouthparts + guts
  • Trematodes (Flukes)- have mouthparts + guts
  • Cestodes (Tapeworms)- absorb nutrients across body surface
28
Q

How long can worms live?

A

Have the potential to live for ~30 years in some cases

29
Q

What are Nematodes? Mechanism of Infection?

A
  • Also termed soil-helminthes or geohelminthes
  • Ingestion of eggs that have matured in soil
  • Eggs hatch in soil and larvae penetrate skin directly
30
Q

Enterobius (Threadworm or Pinworm)

A

Nematodes
Ova transferred from perianal area to fomites
Worm 2-12mm in length
Larvae develop in small intestine, adults reside in colon

31
Q

Symptoms and Treatment of Enterobius (Threadworm or Pinworm)

A
  • Perianal Irritation
  • Weightloss
  • Bedwetting
  • Mebendazole
  • Piperazine
  • Good Hygiene
32
Q

What are Fomites?

A

Objects or materials which are likely to carry infection, such as clothes, utensils, and furniture

33
Q

What are Trematodes?

A

Flat, leaf-shaped worms

34
Q

Liver Flukes

A
  • Freshwater snails are intermediate hosts
  • Encyst on aquatic vegetation that is then consumed by humans
  • Penetrate gut wall and migrate to live (produces systemic allergic symptoms)
35
Q

What are Cestodes?

A
  • Flatworm Phylum

* 15 to 50 mm Long

36
Q

How do Cestodes attach to intestines?

A

They have four ‘suckers’ to adhere to the gut wall

37
Q

How do Cestodes infect humans?

A
  • Arising from anterior region are segmets called proglottids
  • These distally contain eggs
  • Eggs released into faeces and consumed by intermediate hosts
  • Eventually consumed by host (cattle, pigs)
  • Humans consume undercooked meat
  • Results in infection and development usually of a single tapeworm
38
Q

Symptoms of having a Cestode Infection? (9)

A
  • Nutritional Deficiencies
  • Intestinal blockage if intense infestation
  • Nausea
  • Weakness
  • Abdominal Pain
  • Diarrhoea
  • Dizziness
  • Salt Craving
  • Weight Loss
39
Q

Types of Protozoal Infections? (5)

A
  • Amoebea – Entamoeba histolytica (Amboebiasis)
  • Flagellates – Giardia intestinalis (Giardiasis)
  • Coccidia – Cryptosporidium parvum (Cryptosporidiosis)
  • Cilliates – Balantidium coli (Balantidisis)
  • Microspora – Enterocytozoon bieneusi (Microsporidiosis)
40
Q

What is Giardiasis?

A
  • Most common parasitic infection of travellers returning to UK
  • Diarrhoeal disease caused by the microscopic parasite Giardia duodenalis
  • When in gut it can change morphology, mild partial villous atrophy
41
Q

Symptoms and Treatment of Gisardiasis

A
  • Diarrhoea
  • Nausea
  • Anorexia
  • Abdominal Pain
  • If illness is prolonged steatorrhoea is seen
  • Metronidazole 2g/day, 3 days usually does the job
42
Q

What is Steatorrhoea?

A

It is an increase of fat excretion in the stools

Infection (21 decks)

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