(From Dr. Tweeddale’s path lecture, 31 Oct 2000, by Brian Buschman)
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Diarrhea has many causes including viral, bacterial and mechanical. The viral causes include:
1) Rotavirus which infects most kids around the world and is the world’s biggest cause of pediatric gastroenteritis. Adults tend to be immune.
2) Norwalk virus which affects adults.
3) Adenovirus
4) Coxsackie virus
Disaccharide deficiency, specifically lactase deficiency causing unabsorbed lactose, is a mechanical cause of diarrhea. Pancreatic insufficiency, hyperthyroidism, hyperparathyroidism are mechanical causes of diarrhea. Most mess up the osmotic gradient or increase bowel movements. Pancreatic insufficiency causes thick stools.
Bacterial diarrhea can be caused by E. coli, Cholera, Salmonella, Campylobacter, Shigella and Yersinia.
Staph aureus can cause diarrhea by it’s enterotoxins so culture must be taken from the food that was eaten not from the stool.
E. coli has five forms of infection.
1) EPEC is Enteropathogenic E. coli that is usually seen in peds. Think about it as enteropediatric E. coli.
2) EAEC is enteroadherent E. coli that is a cause of travelers diarrhea. It affects travelers but the locals tend to be unaffected.
3) ETEC is enterotoxogenic E. coli for the “Toxic Tweeddale” who is a man of the world. This is the most common form of E. coli infection around the world.
4) EIEC is enteroinvasice E. coli causes lots of blood since it’s actually invasive.
5) EHEH is enterohemorrhagic E. coli is caused by O157:H7 which makes a Shigella like toxin that causes bloody diarrhea after eating undercooked meat.
Shigella is part of the E. coli family and it invades the endothelium and causes bloody diarrhea like EIEC.
Salmonella is part of a class of organisms that include nearly 2000 serotypes. Salmonella is transmitted by the four F’s (flies, fingers, feces, food).
Salmonella typhi is paratyphoid with fever, headache and often they have bradycardia. Usually tachycardia is associated with fever but typhoid is off and an exception. With Typhoid fever you usually also get stupor.
You are able to culture S. typhi at different points along the course of the disease. Week 1 will have constipation and Salmonella is cultureable in the blood. At week 2 you can culture stool after the patient presents with diarrhea and Peyer’s patch involvement. Week 3 will include rose spots on the chest and the Salmonella typhi is so spread out that you can culture it form the urine.
The blood in the stool in S. typhi is from the ulceration of Peyer’s patches.
ETEC and EPEC may not have blood in the stools but you do see blood with EHEC, EIEC, Shigella and Salmonella.
The blood of Salmonella is different from that of Shigella and E coli because it is from ruptured Peyer’s patches. The other two are from ruptures of the endothelium.
Shigella is also unique because man is the only known reservoir. All E. coli and salmonella can be carried as zoonoses, in water or on food.
Shigella is also sneaky and can invade by actin filaments therefore bypassing the blood so as to avoid detection and Ab production.
Cholera causes diarrhea by messing up the normal luminal ion flow. This flow causes osmotic loss of water and severe dehydration. It is treated with glucose hydration where water is given with glucose. The glucose uptake makes the person fat, oh I mean, it causes the water to be taken up.
V. vulnificans causes diarrhea and it comes from shellfish. It’s also a form of necrotizing fasciitis with a purple rash.
Yersinia enterocolitica is a cause of stellate abscesses that also grows on food in the fridge. It likes the cold. It is very slow to plate so you treat it based on clinical presentation while you wait for the culture to come in.
Yersinia enterocolitica can also cause a leg peniculitis. It is an infection of sub-q fat in the leg. Peniculitis can also be caused by Chlamydia or M. leprosae.
Campylobacter is widespread in animals and animal products. It causes bloody diarrhea from ulceration of the bowel.
Many of the enterics also cause a reactive arthritis like:
1) Shigella
2) Salmonella
3) Yersinia
4) Campylobacter
5) C. difficile
As a recap stellate granulomas are caused by:
1) Bartonella (cat-scratch)
2) Yersinia enterocolitica
3) Lymphogranulomas from Chlamydia
Travelers diarrhea is caused by EAEC but it can also be caused by:
1) EIEC
2) ETEC
3) Salmonella
4) Shigella
5) V. vulnificans
6) Gardia lambida
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