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Sem 2 Year 2 > Infections in the GI > Flashcards

Infections in the GI Flashcards

1
Q

What are commensal microorganisms?

A

Normal inhabitants of the body, living in communities
Neither the host (human) or the microbe is harmed and they both derive benefits

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2
Q

How does one acquire their microbiota?

A

Acquired from mother- during pregnancy and birthing and breast feeding
Develop of and modify microbiota throughout life

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3
Q

What benefits do commensal microorganisms give humans?

A

Nutrient and energy extraction from food
Makes a layer and stops other pathogens from growing
Immune system development
Regulation of metabolism
Differentiation of brush border is promoted by bacteria

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4
Q

What benefits do humans give commensal microorganisms?

A

Nutrients and growth factors
A protected habit
Means for spreading- e.g. to children

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5
Q

What are the main types of bacteria present in the colon?

A

Bacteroidetes and firmicutes

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6
Q

What is a opportunistic pathogen?

A

When a commensal organism causes disease by accident

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7
Q

What are the causes of opportunistic pathogens?

A

When they move from the GI e.g. to the urinary tract
When protective mechanisms against bacteria fail in the GI

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8
Q

What is a pathogen?

A

Needs to cause disease to transmit between hosts (evolutionary survival)
Can produce asymptomatic infections

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9
Q

What are zoonotic microorganisms?

A

Commensal or pathogen in an animal that is transmitted to humans directly or by an insect vector
Disease causation in humans is accidental

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10
Q

What are environmental microorganisms?

A

Present in the environment- water, soil, plants
Transmitted to humams by inhalation, direct contact or ingestion
Disease causation in humans is accidental

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11
Q

What are the antimicrobial protective factors in the GI tract?

A

pH- low to kill bacteria in stomach
Low level of O2 which bacteria need to grow
Flow rate washes microorganisms away
Bile salts and digestive enzymes= toxic
Intestinal microbiota is present and stops others growing
Epithelium is tight- barrier
Paneth cells secrete antimicrobial peptides. Also other immune cells

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12
Q

What can cause oppurtunistic pathogens to overcome the protective factors

A

Antacid drugs
Appendicitis= causes stagnantion, good for bacteria to grow
Sepsis- leakage in epithelial cells
Immunosupression
Antibiotics

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13
Q

What virulence factors do pathogens have to help overcome

A

Have adherence mechanisms
Motility- flagellum or pili
Resistance to bile salts and digestive enzymes
Toxic production (can attack epithelium)
Avoidance of immune system via capsules

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14
Q

What makes an oppurtunistic pathogen an obligate pathogen?

A

If they acquire virulence factors

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15
Q

What are the two types of diarrhea that pathogens in the GI can cause?

A

Inflammatory- direct injury to epithelium, releases proteins and blood
Secretory- causes lack of absorbsion of water and electrolytes

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16
Q

Where does helicobacter pylori act?

A

Stomach and duodenum

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17
Q

What type of pathogen is helicobacter pylori and how does it achieve this?

A

Oppurtunistic pathogen- colonised in the human stomach
Present in 50% of western adults
Can survive in acid, does not need much oxygen and produces ureaes which transforms proteins into ammonia- H+ buffering
Is spiral shaped and acts like a cork screw to get through mucus to the epithelium

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18
Q

How is helicobacter pylori spread?

A

Shredded in stools
Can be transmitted through food and water

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19
Q

What are the clinical features of a helicobacter pylori infection?

A

Gastritis- inflammation of stomach
Gastric ulcers
Chronic inflammation= can lead to gastric carcinomas

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20
Q

How do you diagnose a helicobacter pylori infection?

A

Biopsy and histology
Urea breath test (urea will be present)
Antigens in stools

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21
Q

Where does vibrio cholerae effect in the GI?

A

Jejunum and ileum

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22
Q

How does vibrio cholerae get transmitted?

A

Contaminated water or food (especially seafood)

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23
Q

What virulence factors does vibrio cholerae have?

A

Pili- allows adherence
Once adhered starts secreting toxins

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24
Q

What effect do vibrio cholerae toxins have on the small bowel?

A

The toxin will bind to GH1 receptor on the gut wall and get into the cell.
It will activate adenylate cyclase to form cAMP and there will be an increased secretion of chloride ions and reduced absorption of sodium
Therefore will be a net flow of water into the bowel

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25
Q

What are the clinical aspects of vibrio cholerae and how is an infection diagnosed?

A

Watery diarrhoea, no blood only mucus- rice water stools
Severe dehydration
Diagnose via clincal aspects and stool culture

26
Q

What is the treatment of a vibrio cholerae infection?

A

REHYDRATE
Then antibiotics

27
Q

Where in the GI does shigella effect?

A

Large bowel

28
Q

How is shigella transmitted?

A

Contaminated water or food

29
Q

By what mechanism does shigella cause diarrhoea?

A

It is an invasive pathogen- causes inflammation
Enters gut epithelium through M cells which are usually immune cells. Acts like a trojan horse. Gets presented to macrophage and kills macrophage, causing inflammation and cytokine release and tissue destruction

30
Q

What are the clinical features of shigella?

A

Bloody diarrhoea (with pus or mucus), abdominal cramps and fever
Known as dysentery

31
Q

What is the diagnosis and treatment of shigella?

A

Stool culture for diagnoses
Treatment= antibiotics and supportive treatment

32
Q

Where does clostridioides difficile effect in the GI?

A

Large bowel

33
Q

Where are clostridioides difficile spores found?

A

Environment- food, water, hospital environments
Hard to eradicate

34
Q

How does a clostridioides difficile infection occur?

A
35
Q

How do the clostridioides difficile toxins work?

A

Get into the cell and cause overactivity of Rho, a regularity protein which causes cell death
Toxins also pass straight through tight junctions and lead to neutrophil chemotaxis and immune activation

36
Q

What is pseudo membrane?

A

A pseudomembrane is formed when inflammatory exudate rich in fibrin coagulates and causes fibrous areas to form

37
Q

What is the most common cause of nosocomial (originating in a hospital) diarrhoea?

A

Clostridioides difficile

38
Q

What are the clinical features of Clostridioides difficile?

A

Diarrhoea (usually green and smelly), colitis (can be simple, pseudomembranous or fulminant)

39
Q

What is toxic megacolon?

A

Toxic megacolon occurs when swelling and inflammation spread into the deeper layers of your colon. As a result, the colon stops working and widens.

40
Q

What is toxic megacolon?

A

Toxic megacolon occurs when swelling and inflammation spread into the deeper layers of your colon. As a result, the colon stops working and widens.

41
Q

What is the treatment/preventation of Tclostridiodes difficile?

A

Prevention= use specific antibiotics, and hand hygeine, cleaning, PPE
Treatments= antibiotics, faecal transplants and immunotherapy

42
Q

What antibiotics are known to cause clostridiodes difficile?

A

Cephalosporins
Cindamycin
Fluoroquinolones

43
Q

What is gastro-enteritis and what causes it?

A

Inflammation of the digestive tract, causing nausea, vomiting, abdominal pain, diarrhea and fever
Can be caused by viruses, bacteria (infection or intoxication) or parasites

44
Q

What different bacteria causes infection and intoxication?

A

Infection= campylobacter spp, salmonella spp
Intoxication= clostridium perfringes, bacillus cerus, staphylococcus aureus and clostridium botulinum
Both= E coli

45
Q

What will the symptoms be like for gastro-enteritis for the small bowel and the large?

A
46
Q

What is the infective dose and what are some examples of high and low?

A

The number of pathogens needed to cause disease in the new host
Cholerae and E coli= high
Shigella= lower
Viruses and parasites= low

47
Q

What is the commonest cause of diarrhoea in the world and what are the main symptoms?

A

Campylobacter species
Symptoms= blood diarrhoea with fever

48
Q

What are Campylobacter species associated with?

A

Poultry, wild birds and milk

49
Q

What nervous disease can infection with Campylobacter species cause?

A

Guillain barre syndrome

50
Q

What symptoms does salmonella give and what is it associated with?

A

Poultry and eggs
Wide range of clinical manisfestations- fever, diarrhoea that is watery or bloody and vomiting

51
Q

What is clostridium perfringes associated with?

A

Bulk cooking of meat, has spores

52
Q

What symptoms does clostridium perfringes produce and how?

A

Bacteria sporulate in the small intestine and produce an enterotoxin- results in destruction of villi tips with resultant pain and watery diarrhoea
Fever can sometimes occur

53
Q

What condition does clostridium botulinum’s toxins cause?

A

Botulism is a rare but serious illness caused by a toxin that attacks the body’s nerves and causes difficulty breathing, muscle paralysis, and even death
Can effect NMJ, skin or GI

54
Q

Where is clostridium botulinum found?

A

Soils, lake sediments, vegetables, home canned or fermented foods

55
Q

What symptoms does staphylococcus aureus infection give and where does it come from?

A

Very acute vomiting followed by watery diarrhoea
Contaminates salted food and dairy produce

56
Q

What symptoms does bacillus cereus cause and where is it found?

A

Symptoms- acute vomiting followed by diarrhoea
Spores germinate in warm rice

57
Q

What is the most common viral cause of epidemic gastroenteritis worldwide?

A

Norovirus

58
Q

How is norovirus spread?

A

Directly- feco-oral or droplets of vomit
Shellfish

59
Q

How is E coli spread?

A

Food borne- faecal contamination or faecal oral
Environemntal contamination by domestic animals

60
Q

What are the different types of escherichia coli?

A

Toxigenic, pathogenic, invasive and haemorrhagic

61
Q

What food borne diseases peak in winter and summer?

A

Summer= Salmonella, E coli, campylobacter
Winter= norovirus

62
Q

What is the pathophysiology of E coli?

A

Destroys micro villi and enterocytes
Causes watery or bloody diarrhoea and can be with fever or not

Sem 2 Year 2 (16 decks)

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