In our discussion of Gastrointestinal Tract Infections, we come to the very large topic of Infectious Diarrhea and Food Poisoning. We would certainly define it as the acute onset of excessive bowel movements caused either directly or indirectly by microbial pathogens. It’s got a tremendous impact on the world. It’s the second leading cause of morbidity and mortality with 3 million deaths a year and that’s more than 8400 a day and unfortunately it affects our young children in developing countries and main reason for that is that they don’t have a lot of fluid to start with and so if they start losing a lot of fluid, they lose a lot of blood volume and they can get sick in a hurry. Diarrhea is a thousandfold higher in developing countries than in the United States but it still is a problem in the United States with 179 million cases a year, 17 million of which are food-borne, about 2 million of those instances require hospitalization. Three thousand deaths is a sizable amount and most of the deaths occur among elderly persons and if you tally the cost, it’s 6 billion in medical care and lost productivity every year. So, if you’re talking about organisms per 100,000 population,Salmonellaleads the list followed byCampylobacter, Shiga toxin-producingE. coli,VibrioandYersinia. SoSalmonellais quite a big problem in the United States. More about that later. Then as far as the causes of acute bacterial diarrhea if you’re talking about international travel, we’re talking about these organisms.E. coli, the cause of Turista, some people call it Montezuma’s revenge, some people call it the green apple quick step. There are many names for it. One of my colleagues says “Travel broadens the mind and loosens the bowels.” Then it’s a problem in people who work in daycare centers and obviously it’s a problem among food handlers. Well, of course, diarrhea is a pretty common disorder in everybody. Most everybody gets an occasional episode of diarrhea every year and we don’t need medical evaluation for that. So when does a person with diarrhea actually need to see a physician? Well, that would certainly be for perfused watery diarrhea with hypovolemia. In other words, the patient has such volume depletion that when they stand up they feel dizzy or feel like they’re going to faint. Certainly, somebody who has diarrhea along with definite fever, say greater than 38.5 Celsius or if they’ve had diarrhea that’s been lasting more than 48 hours they probably need to be evaluated. A baby with diarrhea because they have such little blood volume anyway, need to be evaluated as do elderly folks. Let’s say a patient who has Crohn’s disease or ulcerative colitis and they often have diarrhea, let’s say they get another episode of diarrhea. Is it the underlying illness or is it some infectious disease problem? We need to know and they need to be evaluated. Somebody with severe abdominal pain that is not common in most benign causes of diarrhea and then someone who has had recent antibiotic treatment for any reason there is a concern for this organism calledClostridium difficilewhich can cause a very severe form of antibiotic- associated diarrhea which can progress to colitis which can even progress to toxic megacolon and death so we need to know if that’s there and that’s causing the diarrhea. Then the immunocompromised patient, a classic example would be the AIDS patient with diarrhea because they may have an unusual organism causing their diarrhea which requires rather unusual treatment. So, more about the clinical features that we need to discern what medications the patient may be receiving. For example, chemotherapy itself. If you know about cancer chemotherapy, it goes after rapidly proliferating tissue. Well, the GI tract has a rapid turnover rate. So you can imagine that diarrhea is a common complication of cancer chemotherapy. So we need to know about that kind of history. We need to know about the sexual history. We talked about some of the sexually transmitted diseases which can be associated with GI symptoms and we need to know about whether patients have pets. There are some zoonotic infections that can be spread from pets to humans and we need to know whether patients are receiving any kind of medications. Now, to figure out what the cause of the diarrhea is, it’s useful to know about the onset. So, if we’re talking about food poisoning, that usually comes on pretty rapidly usually within 2 to 7 hours and vomiting is predominant in food poisoning. In classic one, perhaps the most rapid one, is that caused byStaphylococcus, the enterotoxins ofStaphylococcuscomes on faster than about any form of food poisoning. So we need to know about the recent consumption of things that might haveStaphylococciin them like chocolate eclairs, like mayonnaise, like chicken salad at picnics and things of that nature. We need to know about the duration of symptoms, the stool frequency and the characteristics. Is the patient having small volume stools containing blood and mucus? That suggest an invasive pathogen. We need to know about the presence of severe abdominal pain as we mention. On physical examination, we want to look for evidence of volume depletion. For example, decreased skin turgor. Sometimes it can be pretty subtle and so what you want to do with a typical patient is grasp, say a centimeter of their skin, pinch it together a little gently and see if it stays up. If it sort of tense, that would be evidence of decreased skin turgor. We need to look at the mucous membranes. Are they dry? The other thing that a lot of people forget to check for is orthostatic hypotension. Patient may come in to the emergency room and they’re on a stretcher. Well, we take their blood pressure and it might read 120/80 on a stretcher but if you crack the head of the stretcher up, say 30 degrees, you may find that the blood pressure then drops to 90/70, which is an indication of orthostatic hypotension and rather significant volume depletion. Obviously, we’ll check their temperature and we would hate to miss something like acute appendicitis or other peritoneal signs and by the way it’s hard to evaluate children for peritonitis but if a child comes in to the emergency room and they won’t let you examine them, sometimes if you have them simply jump off a small step. If that causes belly pain when they jump down 1 step, that child may well have peritonitis. Just a little trick for evaluating toddlers. So, if they have fever and peritoneal signs and diarrhea, then that’s usually indicating invasive bugs and invasive enteric pathogen. So when should you go ahead and culture the stool? Well, as I mention in immunocompromised patients, for example AIDS, we would want to know what is growing in the stool. Patients who have other comorbidities particularly diabetics, patients with ulcerative colitis or Crohn’s disease. We need to distinguish, as I mention, infection from a flare of their disease. Food handlers may be required to get a stool culture to prove that the pathogen is no longer there so that they can return to work. Healthcare workers for the same reason. It would be sad for a healthcare worker to pass on a cause of diarrhea to one of their sick patients. Same thing goes for daycare attendees or employees and institutionalized persons because there are certain causes of diarrhea that run rampant in institutions. Now, if a physician decides that a stool culture is indicated, it is very helpful to the laboratory if the physician will specifically request culturing for a suspected pathogen that helps the lab isolate the right bug.