Week 9 - Microbiology of the GIT Flashcards
What embryological remnant lies within the falciform ligament?
The umbilical vein lies within the ventral mesogastrium during development: develops into ligamentum teres, which is the round ligament of the liver
What conditions could result from stone obstruction of the cystic duct?
- Cholecystitis
2. Biliary colic
What conditions could result from stone obstruction of the common bile duct?
- Cholangitis
2. Jaundice
Outline suitable investigations for dysphagia to solid food.
- Barium swallow
- Oesophago-gastro-duodenoscopy
- Video fluoroscopy
- CXR for external compression
Is the peritoneal cavity an enclosed space?
- In males - enclosed space
2. In females, it is open to the external environment via the infundibulum of the Fallopian tubes
What differences exist in the abdominal wall above and below the arcuate line?
- The rectus muscles are surrounded by the aponeurosis of the other abdominal wall muscles
- Both anterior and posterior to them above the arcuate line
- Only anterior below it
What kind of pain do midgut derivatives produce?
- Intra-peritoneal midgut structures convey a vague periumbilical pain
- When pathology is irritating/distending their visceral peritoneum
What is a Meckel’s diverticulum?
Diverticulum that exists because of the incomplete obliteration of the vitelline duct (omphalomesenteric duct)
With reference to local organs, describe the site of the lesser sac.
Posterior to the liver, lesser omentum and the stomach
It lies immediately anterior to the pancreas
How does the lesser sac form during development in the human?
- The foregut has both a ventral and dorsal attachment to the abdominal cavity
- When the foregut rotates, an enclosed space is created posterior to the stomach - this is called the lesser sac
If you were to insert the tip of your finger into the foramen of Winslow, name 2 tubular structures that would be lying in the peritoneum anterior to your finger.
- Common hepatic artery
- Common bile duct
- Portal vein
Explain why a cancer of the head of the pancreas should cause a patient to be jaundiced.
- A cancer in the head of the pancreas can obstruct the common bile duct as it enters the duodenum
- This will stop bile from following its normal passage into the gut causing a backlog of bile within the biliary system
- As a consequence of this, constituents of bile like bilirubin will be reabsorbed into the blood causing a hyperbilirubinaemia
What is meant by the term obligate anaerobes?
These microorganisms are unable to survive in the presence of oxygen (at least at atmospheric pressure). They survive and thrive in the absence of oxygen.
Which parts of the GIT are predominantly anaerobic zones?
- Parts of the mouth
- Small bowel
- Colon
Describe four beneficial roles that bacteria play in the human GIT.
- Prevent colonisation of pathogens
- Stimulate development of mucosal associated lymphoid tissue
- Stimulate production of natural antibodies
- Kill non-indigenous bacteria
- Assist in the digestion of certain polysaccharides
- Play a role in the synthesis of certain vitamins - Vitamin B12, K
A man with a prosthetic heart valve needs some wisdom teeth removed. Explain why he might receive prophylactic antibiotics.
- Mouth contains a high concentration of bacteria
- Dental procedures (in fact brushing and flossing) cause a bacteraemia - presence of bacteria in the blood - which can increase the chance of a prosthetic heart valve being colonised by these bacteria
- Prosthetic heart valves can be colonised more easily than normal valves leading to infection of the endocardial surface of the heart - infective endocarditis
- Giving prophylactic antibiotics is thought to reduce the duration of bacteraemia and hence the likelihood of the heart valve being colonised
What are the differences between septicaemia and bacteraemia?
- Septicaemia: clinically significant presence of microbes in the blood stream
- In the absence of any clinical signs, the presence of bacteria in the blood is termed bacteraemia
Should a patient with tonsilitis immediately be prescribed antibiotics?
- Most cases of tonsilitis are caused by viruses
- Decision to give antibiotics should be based on the presence of tonsillar exudates or signs of secondary pharyngitis
- Most patients should just receive supportive treatments to reduce their pain and fever and to maintain adequate hydration
A patient is about to undergo surgery to remove a portion of her small intestine. Outline a suitable prophylactic antibiotic regime.
- Prophylactic antibiotics should include something to kill the anaerobic bacteria (metronidazole)
- Something that acts on a wide range of the remaining bacteria (so called broad-spectrum agents) like gentamicin or a cephalosporin
How is norovirus spread?
- Faecal oral route
- Person to person contact
- Via aerolisation of the virus
What is the normal incubation period of the norovirus?
Normally 1-2 days
State some important symptoms of norovirus infection.
- Profuse vomiting (non bloody, non bilious)
- Watery diarrhoea
- Abdominal cramps
- Headache
- Low grade fever
How might you assess dehydration?
- Assessment of mucous membranes, skin turgor and whether or not the person has sunken eyes
- Signs of shock in severely dehydrated patients: tachycardia, tachypnoea
- Individual might mention that they have not passed much urine
How long does a norovirus infection typically last?
1-3 days
How can a norovirus infection be treated?
No specific treatment
Supportive measures: correct fluid and electrolyte intake
How would you define Traveller’s Diarrhoea?
Production of three or more loose watery stools during or shortly after travelling abroad
Entero-toxigenic E. coli (ETEC) is a common cause of traveller’s diarrhoea. What type of bacteria is this?
Facultatively anaerobic gram negative rod
What type of diarrhoea is commonly associated with this Enterotoxigenic E. coli infection?
Watery diarrhoea without blood or mucus
Briefly outline the mechanism by which enterotoxigenic E. coli causes infection.
- ETEC colonise the mucosal surface of the small intestine
- The bacteria use fimbrial adhesions (projections from the bacterial cell surface) to bind enterocyte cells in the small intestine
- Adhesion to the mucosal epithelial cells allows for transfer of enterotoxins produced by ETEC bacteria which stimulate the release of liquid from cells lining the intestinal walls
- ETEC make 2 toxins: heat labile and heat stable that cause intestinal epithelial cells to secrete excess fluid
- Some strains only produce one of the toxins, while others produce both
Outline the clinical presentation of enterotoxigenic E. coli infection.
- Production of abundant watery diarrhoea
- Abdominal cramping
- Fever
- Vomiting
- Chills
- Headaches
- Muscle aches
- Bloating
State 2 common causes of traveller’s diarrhoea.
- Shigella
2. Salmonella spp
What are the most common organisms associated with gastroenteritis?
Strains of:
- Campylobacter
- Salmonella
- Listeria
Which organisms can produce toxins that cause gastroenteritis?
- Staphylococcus
2. Clostridium
