Intestinal Microbiology

Question 1

what is the microbiome?

Answer 1

Complex, interactive, community and ecosystem containing over 1,000 bacterial species

Question 2

Anaerobes outnumber

Answer 2

facultative anaerobes

Question 3

Microbiota is sparse in the

Answer 3

stomach and upper intestine (duodenum, jejunum and upper ileum)

Question 4

microbiota is extensive in

Answer 4

the lower bowel

Question 5

Bacteria occur in both the

Answer 5

lumen and attached to the mucosa but do not normally penetrate the bowel wall

Question 6

describe normal microbiota

Answer 6

symbiotic, mutualistic relationship

Question 7

describe pathogenic microbiota

Answer 7

opportunistic

Question 8

Normal Microbiota in the blood stream or peritoneal cavity will become

Answer 8

pathogenic

Question 9

Colonisation of the upper digestive tract is an abnormal event and characteristic of

Answer 9

certain pathogens, for example:

Vibrio cholerae (cholera)
escherichia coli (gastroenteritis)
helicobacter pylori (stomach ulcer)

Question 10

the appendix is known as…

Answer 10

… the seed house for th ehuman gut microbiome

Question 11

gastric aci dkills most…

Answer 11

… organisms that are swallowed

Question 12

gastric acid results in

Answer 12

high incidience of bacterial colonisation / bacterial diarrhoeal disease

Question 13

bile has

Answer 13

antibacterial properties

Question 14

how does peristalsis help control normal microbiome balance?

Answer 14

• Forward motility suppresses Microbiota of upper bowel

Question 15

describe the microbiome

Answer 15

• Produce their own anti-bacterial substances
• Bacteriocins and short chain fatty acids
• These stabilise normal populations and prevent implantation of pathogens

Question 16

the microbiome is extremely diverse and capable of using virtually any compound in the intestinal lumen as a

Answer 16

substrate

Question 17

Endogenous substances
that undergo
enterohepatic circulation:

Answer 17

• Bilirubin
• Bile acids
• Cholesterol
• Oestrogens

Question 18

Intestinal bacteria metabolise bile acids rendering
them

Answer 18

more easily absorbed by the intestinal mucosa -
Contributes to enterohepatic circulation

Question 19

Many drugs that are excreted by the liver (digitalis,
morphine, rifampin, chloramphenicol) and antibiotics
block

Answer 19

enterohepatic circulation by suppressing intestinal
microbiota.

Question 20

Enzymes produced by intestinal bacteria produce some important vitamins:

Answer 20

Vitamin K
Vitamin A
Thiamine
Folic Acid
BIotin

Question 21

22

Question 22

Intestinal microbiome relatively stable over time and discourages

Answer 22

infections by exogenous pathogens and prevents overgrowtho of potentially pathogenic members,

Question 23

antibiotics can upset

Answer 23

microbiome balance and may leave the intestine open to infection eg: salmonella

Question 24

Healthy individuals are often resistant to

Answer 24

salmonella and wuite a large incolum is required to initiate infection.

Question 25

antibiotics sppress

Answer 25

intestinal microbiota -> individual becomes more susceptible.

Question 26

Clostridium difficile: Causes

Answer 26

GI infection due to bacterial overgrowth and results in severe inflammation of the colon

Question 27

how is C. difficile GI infection initiated?

Answer 27

Initiated by suppression of normal microbiome with antibiotics.

Question 28

what is Peritonitis?

Answer 28

breach of the mucosal wall by trauma allows entry of bacteria into a normally sterile area.

Question 29

Poor circulation, low oxygen supplies and dead tissue favour the growth of

Answer 29

anaerobic bacteria which results in peritoneal abscesses

Question 30

Several enterotoxin-producing bacteria cause diarrhoeal disease

Answer 30

* Vibrio cholerae * E. coli * Shigella * Staphyloccoccus aureus * Clostridium perfringens

Question 31

Diarrhoea induced by pathogens →

Answer 32

guts react to toxins and contract.

Question 33

Diarrhoea induced by pathogens causes

Answer 33

expulsion defence mechanism and diarrhoea

Question 34

Diarrhoea Treatment

Answer 34

* Opioid-receptor agonist drugs * Diphenoxylate / Loperamide / Morphine * µ-opioid receptor agonist inhibits the myenteric plexus (motor activity) of the large intestine * Loperamide: Low CNS absorption through BBB * Morphine: high absorption * Decrease muscle tone of the intestines > reduce GI activity

Question 35

fluid from the body is normally

Answer 35

pumped into the intestinal lumen during digestion

Question 36

Fluid from the body is normally pumped into the intestinal lumen during digestion. - this fluid is typiclly

Answer 36

isotonic with blood because it contains a high concentration of Na+.

Question 37

how much Na+ will a healthy individual secrete per day

Answer 37

A healthy individual will secrete 20-30 grams of Na+ per day via intestinal secretions.

Question 38

A healthy individual will secrete 20-30 grams of Na+ per day via intestinal secretions. Nealy all of htis is

Answer 38

reabsorbed by the intestine, helping to maintain constant Na+ levels in the body (homeostasis)

Question 39

Heavy continuous diarrhoea can become

Answer 39

a potentially life threatening condition within hours.

Question 40

Liquid secreted into the intestinal lumen passes through the

Answer 40

gut so quickly that little Na+ is reabsorbed

Question 41

* Heavy continuous diarrhoea can become a potentially life threatening condition within hours. * Liquid secreted into the intestinal lumen passes through the gut so quickly that little Na+ is reabsorbed * Leading to...

Answer 41

... dangerously low sodium levels in the body (severe hyponatremia).

Question 42

what are the 3 main characteristics of diarrhoeal diseases?

Answer 42

1) Intestinal fluid loss, related to the action of an enterotoxin on the small bowel epithelial cells. 2) Organism does not invade the mucosal surface – colonises the upper small bowel adhering to the epithelial cells and producing the enterotoxin. 3) Faecal effluent (originating from the upper intestine, where the toxin is most active) is watery and often voluminous – clinical dehydration

Question 43

what is cholera causes by?

Answer 43

Caused by Vibrio cholerae usually ingested in contaminated water

Question 44

cholera stool volume?

Answer 44

Stool volume can exceed 1 L/h with daily faecal outputs of 15-20 L if the patient is kept hydrated

Question 45

30+