Infections in the GI

Question 1

What are commensal microorganisms?

Answer 1

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

Question 2

How does one acquire their microbiota?

Answer 2

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

Question 3

What benefits do commensal microorganisms give humans?

Answer 3

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

Question 4

What benefits do humans give commensal microorganisms?

Answer 4

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

Question 5

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

Answer 5

Bacteroidetes and firmicutes

Question 6

What is a opportunistic pathogen?

Answer 6

When a commensal organism causes disease by accident

Question 7

What are the causes of opportunistic pathogens?

Answer 7

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

Question 8

What is a pathogen?

Answer 8

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

Question 9

What are zoonotic microorganisms?

Answer 9

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

Question 10

What are environmental microorganisms?

Answer 10

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

Question 11

What are the antimicrobial protective factors in the GI tract?

Answer 11

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

Question 12

What can cause oppurtunistic pathogens to overcome the protective factors

Answer 12

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

Question 13

What virulence factors do pathogens have to help overcome

Answer 13

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

Question 14

What makes an oppurtunistic pathogen an obligate pathogen?

Answer 14

If they acquire virulence factors

Question 15

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

Answer 15

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

Question 16

Where does helicobacter pylori act?

Answer 16

Stomach and duodenum

Question 17

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

Answer 17

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

Question 18

How is helicobacter pylori spread?

Answer 18

Shredded in stools
Can be transmitted through food and water

Question 19

What are the clinical features of a helicobacter pylori infection?

Answer 19

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

Question 20

How do you diagnose a helicobacter pylori infection?

Answer 20

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

Question 21

Where does vibrio cholerae effect in the GI?

Answer 21

Jejunum and ileum

Question 22

How does vibrio cholerae get transmitted?

Answer 22

Contaminated water or food (especially seafood)

Question 23

What virulence factors does vibrio cholerae have?

Answer 23

Pili- allows adherence
Once adhered starts secreting toxins

Question 24

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

Answer 24

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

Question 25

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

Answer 25

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

Question 26

What is the treatment of a vibrio cholerae infection?

Answer 26

REHYDRATE Then antibiotics

Question 27

Where in the GI does shigella effect?

Answer 27

Large bowel

Question 28

How is shigella transmitted?

Answer 28

Contaminated water or food

Question 29

By what mechanism does shigella cause diarrhoea?

Answer 29

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

Question 30

What are the clinical features of shigella?

Answer 30

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

Question 31

What is the diagnosis and treatment of shigella?

Answer 31

Stool culture for diagnoses Treatment= antibiotics and supportive treatment

Question 32

Where does clostridioides difficile effect in the GI?

Answer 32

Large bowel

Question 33

Where are clostridioides difficile spores found?

Answer 33

Environment- food, water, hospital environments Hard to eradicate

Question 34

How does a clostridioides difficile infection occur?

Answer 34

Question 35

How do the clostridioides difficile toxins work?

Answer 35

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

Question 36

What is pseudo membrane?

Answer 36

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

Question 37

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

Answer 37

Clostridioides difficile

Question 38

What are the clinical features of Clostridioides difficile?

Answer 38

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

Question 39

What is toxic megacolon?

Answer 39

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

Question 40

What is toxic megacolon?

Answer 40

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

Question 41

What is the treatment/preventation of Tclostridiodes difficile?

Answer 41

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

Question 42

What antibiotics are known to cause clostridiodes difficile?

Answer 42

Cephalosporins Cindamycin Fluoroquinolones

Question 43

What is gastro-enteritis and what causes it?

Answer 43

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

Question 44

What different bacteria causes infection and intoxication?

Answer 44

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

Question 45

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

Answer 45

Question 46

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

Answer 46

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

Question 47

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

Answer 47

Campylobacter species Symptoms= blood diarrhoea with fever

Question 48

What are Campylobacter species associated with?

Answer 48

Poultry, wild birds and milk

Question 49

What nervous disease can infection with Campylobacter species cause?

Answer 49

Guillain barre syndrome

Question 50

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

Answer 50

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

Question 51

What is clostridium perfringes associated with?

Answer 51

Bulk cooking of meat, has spores

Question 52

What symptoms does clostridium perfringes produce and how?

Answer 52

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

Question 53

What condition does clostridium botulinum's toxins cause?

Answer 53

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

Question 54

Where is clostridium botulinum found?

Answer 54

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

Question 55

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

Answer 55

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

Question 56

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

Answer 56

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

Question 57

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

Answer 57

Norovirus

Question 58

How is norovirus spread?

Answer 58

Directly- feco-oral or droplets of vomit Shellfish

Question 59

How is E coli spread?

Answer 59

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

Question 60

What are the different types of escherichia coli?

Answer 60

Toxigenic, pathogenic, invasive and haemorrhagic

Question 61

What food borne diseases peak in winter and summer?

Answer 61

Summer= Salmonella, E coli, campylobacter Winter= norovirus

Question 62

What is the pathophysiology of E coli?

Answer 62

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