Gut Flora Flashcards
What is microbiota?
Normal flora.
What is tissue tropism?
Tissue tropism is the ability of a pathogen to infect a particular tissue.
What are fimbriae?
Appendages that can be found on many Gram-negative and some Gram-positive bacteria that is thinner and shorter than a flagellum used for attachment to surfaces.
How does the number of bacteria change with distance from the stomach?
Flora increase in numbers with distance from the stomach.
Which flora are present throughout from the stomach to the colon?
Gram-positive flora.
Which flora are only present from the ileum onwards?
1 - Anaerobes.
2 - Coliforms.
What is the difference between gram positive and gram negative bacteria?
- Gram positive bacteria have a thick, multi-layered peptidoglycan wall, whereas gram negative have a thin, single-layered one.
- Gram positive bacteria have no outer membrane, whereas gram negative bacteria do.
- Gram positive bacteria retain crystal violet dye and stain purple. Gram negative bacteria need a counter stain to stain red or pink.
What counterstains might be used to stain gram negative bacteria?
Safranin or fuschine.
List 3 defences the pharynx has against harmful microorganisms.
1 - Flow of liquids.
2 - Lysozymes.
3 - Normal flora.
List 2 defences the oesophagus has against harmful microorganisms.
1 - Peristalsis.
2 - Flow of liquids.
What defence does the stomach have against harmful microorganisms?
Low pH.
List 6 defences the small intestine has against harmful bacteria.
1 - Peristalsis.
2 - Flow of liquids.
3 - Shedding of epithelium.
4 - Peyer’s patches (ileum).
5 - IgA.
6 - Mucus.
What are Peyer’s patches?
Masses of lymphatic tissue found throughout the ileum of the small intestine.
What is a glycoalyx?
A pericellular matrix made of a glycoprotein and glycolipid covering that surrounds the cell membranes of some bacteria.
How do salivary glands defend against harmful microorganisms?
- They secrete a buffered neutral pH solution that neutralises bacterial acids.
- They secrete lysozymes that attack bacterial peptidoglycan.
How do microbiota help make the environment unfavourable for exogenous bacteria?
Their metabolic byproducts contribute to this environment.
What can cause polymicrobial mediastinitis?
- Ccan be caused by perforation of the oesophagus.
- Inflammation of the mediastinum due to microbial infection.
How might liver cirrhosis cause microbial infection of the peritoneum?
- In liver cirrhosis, portal hypertension occurs.
- Instead of being cleared from the liver, bacteria in the portal vein enter peri-hepatic lymphatics.
- From there, they reach the peritoneum.
What are diverticula?
Herniations of the mucosa and submucosa through the outer muscle layer of the larger intestine, causing pouches to form.
List 3 relatively antibiotic resistant bacteria that might replace normal flora after using antibiotics.
1 - Enterobacter.
2 - Pseudomonas spp.
3 - Candida albicans.
Where can Campylobacter spp be found?
What can result from hosting it?
- It is part of the normal flora of the chicken intestine.
- Consuming an undercooked contaminated chicken carcass can result in gastroenteritis.
Where can Escherichia coli be found?
How is it transmitted?
- It is a part of the normal flora of farm animals.
- Transmitted via touch.
List 3 syndromes and diseases caused by Escherichia coli.
1 - Haemorrhagic colitis.
2 - Haemolytic uraemic syndrome.
3 - Renal failure.
In which environment can Clostridium difficile proliferate?
Where normal flora are absent due to antibiotics.
What toxins does Clostridium difficile release?
- What do these toxins do to the GIT?
- B cytotoxin.
- A enterotoxin.
- These toxins damage enterocytes.
List 7 infections that may be caused by normal flora.
1 - Abscesses.
2 - Pharyngitis.
3 - Sepsis (inflammatory immune response).
4 - Endocarditis.
5 - Pneumonia.
6 - Gastroenteritis.
7 - Urogenital infections.
Give an example of a cause of appendicitis.
If a faecolith obstructs the lumen of the appendix, normal flora can reproduce behing the faecolith.
List 2 bacteria that can cause liver abscesses.
1 - Enterococcus spp.
2 - Streptococcus spp.
List 2 major bacteria of the jejunum.
1 - Enterococci.
2 - Lactobacilli.
