4.1 Infections of the GI tract PART I Flashcards
(32 cards)
What can be used to classify stools?
What do these indicate?
The Bristol Stool Chart
Type 1: separate hard lumps, indicates very constipated
Type 3 and 4: NORMAL
Type 7: liquid consistancy with NO solid pieces, indicates inflammation
Define gastroenteritis
What is the primary manifestation?
A nonspecific term for various pathological states of the GI tract.
Defined as-Inflammation of the mucous membrane of both the stomach and intestine, usually causing diarrhea, nausea, vomiting and abdominal cramps
Primary manifestation is diarrhea but often accompanied by symptoms above
Give 4 causes of Gastroenteritis
1) GI Obstruction
2) Trauma
3) Food poisoning
4) GI Inflammation
What are the 2 main causes of Infectious Gastroenteristis?
Pre-formed toxins (food poisoning)
Living Organisms (helminths, virus, bacteria)
List the non-invasive and invasive mechanisms organisms can use to infect the GI tract
List one organism for each
Non-invasive:
- organisms colonize the gut and produce the toxin (e.coli)
- organisms bind to brush border (cryptosporidium)
Invasive:
- organisms penetrate the mucosal layer (shigella) or deeper (S.typhi)
What are nematodes? Name 4 types
Round bodied worms
- Hookworms
- Roundworms
- Pinworms
- Whipworm
What are Hookworms and how are they commonly contracted?
What feature of hookworms makes them able to infect and how does it do this?
What is a common sign
These are round bodied nematodes contracted through contaminated food
The mouth area has the ability to grasp onto the epithelia ➞ the egg or cyst is ingested and in the right environment will hatch into small worms
Sign: red appearance on skin due to worms moving and burrowing through
What are round worms and how are they commonly contracted?
What is a common symptom and why?
Why can they lead to breathing problems?
What is a visible sign that can be seen in severe cases?
These are a type of round bodied nematode that are commonly contracted through ingestion of contaminated soil or meat
Symptom: “acute abdominal pain” due to build up of worms within intestines that cause severe blockages
They can circulate body and reach other sites such as lungs leading to breathing problems
In severe cases the worms can be seen by the naked eye moving throughout body (eg. through nasal cavity)
What are pinworms are who do they commonly affect?
How do they travel and why are they particularly spreadable?
What are 4 signs of pinworms?
These are roundbodied nematodes that commonly affect children
Ingestion of egg travels through intestines and resides ➞ at night female worms will travel through intestine to the anus and lay eggs in a sticky substance ➞ this substance has a small reaction with the skin, causing itchiness ➞ itching causes transfer of eggs onto fingernails and anywhere the hand touches after
Signs: visible detection in faeces, malaise, anaemia, development of darkness under eyes
Which type of nematode is associated with an anal prolapse?
Whipworm (Trichuris trichiura)
What are cestodes and how are they spread?
Name one example and how it is commonly spread
Cestodes are segmented flat-bodied worms that are commonly spread through the ingestion of meats
Eg. tapeworm
What are trematodes and give 2 examples?
Trematodes are flatworms that are non-segmented
Eg. flukes or schistosomes
What immune cell is key in defending against parasitic worms?
What is its structure and how does this aid function?
Eosinophils: bi-lobed nucleus and cytoplasm filled with granules containing enzymes and proteins
They contain a chemical compound directed at the nervous system of worms
What are Schistosomiasis and how are they commonly contracted?
Name 3 signs of this infection
Schistosomes are trematodes that flatbodied are non-segmented
They are ususally a tropical disease and commonly infect ‘intermediates’ (such as snails and soil). These can then infect humans through skin touch.
Signs: swollen abdomen, increased vascularisation, rashes
What is the difference between: food poisoning, food infection and food intoxication?
Food Poisoning is any illness resulting from the consumption of food
Food infection refers to the presence of bacteria or other microbes which infect the body after consumption
Food intoxication refers to the ingestion of toxins contained within the food
Which organism is the leading bacterial cause of food poisoning, give 4 features of this bacteria
How does infection by this bacteria lead to common symptoms of food poisoning?
How would you treat and why?
Staphylococcal aureus
It is a commensal bacteria that is salt tolerant, heat stable and produces five enterotoxins (A-E) making it resistant to gut enzymes. It also changes its genes very fast
Entertoxins stimulate intestinal muscle contractions ➞ leads to nausea, abdominal cramping, vomiting and diarrhea. Onset is ususally 1-6hours
Treatment is usually just replacement of fluids and electrolytes as the infection is normally mild and self-limiting
Give 6 general symptoms of food poisoning
nausea, vomiting, diarrhoea, abdominal cramping, bloating, fever
How do enterotoxins pass through the villi and how does this result in vomiting and watery diarrhoea?
Enterotoxin utilises goblet cells and epithelial cells to passage through into lamina propria
Once in lamina propria two thing happen:
1) Immune response ➞ increase in 5HT acts on vagus nerve which stimulates vomiting
2) Inflammatory response ➞ disrupts passage of substances through epithelia causing damage and leading to watery diarrhoea
Venous blood gas status depends on whether we have more vomiting or diarrhoea
What would an ABG show if vomitting is the main cause of fluid loss?
What would an ABG show if diarrhoea is the main cause of fluid loss?
Vomiting: hypochloremia, metabolic alkalosis, hypokalemia (low Cl-, K+ H+)
Diarrhoea: metabolic acidosis and hypokalemia (high H+ and low K+)
Why is reheating food an ineffective method of preventing food poisoning by S. aures?
Reheating food eliminates the staphylococci but NOT the enterotoxin produced
Describe the stucture of Clostridium Perfringes
gram +, rod shaped, spore forming and anaerobic
Describe the mechanism of infection by clostridium perfringes and how this results in watery diarrhoea
1) once ingested produces an enterotoxin which can enter the natural protective layer of our microbiota, through epithelium and lamina propria
2) triggers an inflammatory response which weakens epithelial cells making them prone to furthur entry of C.perfringes
3) Increased bacterial invasion, replication and enterotoxins results in more inflammation which furthur dirupts and damages epithelium
4) eventually there is complete breakdown of epithelium ➞ incorrect passage of ions ➞ large amounts of water enters lumen ➞ watery diarrhoea
What is meant by “emetic” and “diarrhoeal” causes?
Emetic: cooked food left at room temperature too long
DiarrhoeaI: meat and ready prepared meals that have been incorrectly stored
What is the most common cause of infectious diarrhea in the western world?
How are they commonly contracted?
Viral gastroenteritis: specifically the Norovirus which is the leading non-bacteria cause of gastroenteritis
Commonly contracted through contaminated food/water
Viral gastroenteritis produces symptoms similar to bacterial gastroenteritis but are much milder
