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Infectious diarrhea

We are now going to turn to the consideration of diarrheal diseases. While diarrhea in this country is an annoyance, throughout the world, it is a major cause of death. As a matter of fact, it is the second most common cause of death in the world diarrhea, diarea, diarrea. This mainly occurs in young infants who don't withstand diarrhea very well. In the U.S. we have about one bout of gastroenteritis per person per year, with some having many more and some not having any.

The number of organisms required to cause diarrhea has been worked out with many of the infecting agents. Among the bacteria, shigella and E. coli 0157 seem to be in a class by themselves. Shigella is very, very infective. One or two shigella organisms are capable of causing infection. With E. coli 0157, it is less than one thousand. With organisms such as salmonella and the enterotoxin-producing E. coli, which causes turista in travelers in Mexico and other countries, you need many more organisms to cause infection, usually in the millions. Campylobacter jejuni is somewhere in between. What is really interesting is that the protozoa - Giardia, E. histolytica and Cryptosporidium - require very low inocula.

We have good host defenses in our GI tract against the organisms that produce diarrhea, but many of these suffer as we get older. We lose our gastric acidity; with certain types of illnesses and with certain drugs we take, we may lose intestinal motility. Intestinal motility is also a host defense. when we take antibiotics and decrease or change bacterial flora in the colon.

E. coli produces the enterotoxin; there is superficial inflammatory disease where the bacteria invades, but only invades superficially and produces ulceration and the classical example there is shigella; there is the superficial inflammatory disease produced by a cytotoxin which also produces ulceration and these are the E. coli that produce the cytotoxin E. coli 0157.

If you look at the mechanism and what the organisms are, exogenous production of enterotoxin, S. aureus, which can produce it in the food and then you ingest the preformed toxin and get - with a very short incubation period - vomiting and diarrhea. Then you can ingest the organism which multiplies in the gut and produces its enterotoxin in the gut.

E. coli, which is very uncommon in this country, Vibrio parahaemolyticus, the cytotoxin C. difficile and E. coli 0157; these do not invade but they produce a toxin that causes ulceration. Then the submucosal deep invasion is caused by salmonella, Yersinia and Campylobacter. Then there are a group of viruses that can cause gastroenteritis, diarrhea, Rotavirus, parvovirus.

Food from animals, especially poultry, are heavily contaminated with salmonella and Campylobacter. These are natural organisms found in the guts of chickens, pigs, cows and many other animals, but particularly in poultry. Day care is an incubator for Rotavirus, Giardia, Cryptosporidium and in fact, practically anything that is communicable. In this country, when Cryptosporidium was first identified as an important organism in patients with HIV.

Antibiotic therapy is closely associated with C. difficile infection or resistant organisms such as Campylobacter and resistant salmonella. When we see people with prominent vomiting, we think in terms of preformed toxin or viral infection. When there are no fecal leukocytes, there is no blood and there is no mucus, we think of enterotoxin. Also, you do not get fever with enterotoxic infection. With viral infection, there are no fecal leukocytes, blood or mucus, but you may have fever. In the presence of fever but a stool that looks like it is enterotoxic, in terms of no leukocytes, blood or mucus, you are dealing with a viral illness.

When fecal leukocytes occur or there is blood or mucus, with or without fever, you have to think in terms of invasive or cytotoxic disease. Pseudo-appendicitis or mesenteric adenitis is strongly associated with Yersinia outbreaks. You'll have one hundred people with diarrhea.

E. coli 0157 is strikingly associated with hemolytic uremic syndrome, or thrombotic thrombocytic purpura; it is probably the same syndrome. E. coli 0157 diarrhea will develop hemolytic uremic syndrome, or TTP, one to two weeks after the diarrhea.

When should we do fecal white cell tests? When should we take a culture? When should we treat? Anybody who has an acute onset of symptoms that are mild to moderate and especially if they are getting better by the time you see them or hear about them, there is no need to do anything.

There is controversy over whether E. coli 0157 increases the risk of the hemolytic uremic syndrome. There have been some reports indicating that in fact treatment does increase the risk. However, treatment also shortens the syndrome and we do advocate treatment, even though theoretically you may be increasing the risk, to a small degree, of hemolytic uremic syndrome.

If you know you are dealing with a Campylobacter, about thirty percent of them are now resistant to quinolones in this country. So you would use erythromycin or azithromycin if you knew it was a Campylobacter.

The key to therapy of diarrhea, particularly in children, is rehydration. There are very rehydrating, commercially available things, such as Pedialyte or Rehydralyte, one could use Gatorade - there are all kinds of different mixtures. The idea is to give fluid and electrolytes. Loperamide or Lomotil can be used.

There are delayed, noninfectious complications of diarrhea. I have mentioned the hemolytic uremic syndrome with E. coli 0157, a very severe disease with a significant mortality rate. One interesting fact that you may or may not have heard is that one-third of cases of Guillain-Barre syndrome follow Campylobacter gastroenteritis, which is really an extraordinary figure. When Guillain-Barre syndrome occurs, one-third of them have followed Campylobacter gastroenteritis. Reiter's syndrome, or reactive arthritis, may follow.

One of the most over-done studies is sending stool for ova and parasites. You should never consider sending a stool for ova and parasites unless the symptoms have been present for at least two days and that is really a minimum number of days, plus something else that would indicate the possibility of protozoal infection or worm infection.

In amoebiasis, as I mentioned, there are ulcerations; this is an invasive organism. Most commonly, the cecum is involved, but there may be other areas of involvement along the gut, including the ascending colon or rectum. There are no or few fecal leukocytes and of course, the diagnosis is made by examining the stool for parasites. There are now PCR and ELISA techniques being developed, so there will be much more specific and sensitive testing available.