Pathophysiology:

Inflammatory diarrhea is caused by the action of cytotoxin on the mucosa, leading to its invasion and destruction. The colon or the distal small bowel commonly is involved. The diarrhea usually is bloody, with the presence pus comprised of leukocytes. Sometimes, the organisms penetrate the mucosa and proliferate in the local lymphatic tissue, followed by systemic dissemination and sepsis. Examples include Campylobacter jejuni, Vibrio parahaemolyticus, enterohemorrhagic and enteroinvasive E coli, Yersinia enterocolitica, Clostridium difficile, Entamoeba histolytica, and Salmonella and Shigella species.

In some types of food poisoning (e.g., staphylococci, B cereus), vomiting is caused by a toxin acting on the central nervous system. For example, the clinical syndrome of botulism results from the inhibition of acetylcholine release in nerve endings by the botulinum.

The pathophysiological mechanisms that result in acute gastrointestinal symptoms produced by some of the noninfectious causes of food poisoning (naturally occurring substances [e.g., mushrooms, toadstools] and heavy metals [e.g., arsenic, mercury, lead]) are not well known.

Frequency:

History:

The following are some of the salient features of food poisoning: Diarrhea in food poisoning usually lasts less than 2 weeks. If it persists longer than 2 weeks, it is considered chronic and food poisoning is a less likely cause; the presence of fever suggests an invasive disease. However, sometimes fever and diarrhea may result from infection outside the gastrointestinal tract, as in malaria; a stool with blood or mucus indicates ulceration of the large bowel. Bloody stool without fecal leukocytes should raise the suspicion of enterohemorrhagic E coli infection; a bulky whitish stool suggests the involvement of the small intestine, causing malabsorption; a profuse rice-water stool indicates cholera or a similar process; abdominal pain is most severe in inflammatory processes. Painful abdominal muscle cramps suggest underlying electrolyte loss, as in severe cholera; a history of bloating and malodorous gas should raise the suspicion of giardiasis; Yersiniaenterocolitis often mimics the symptoms of appendicitis; tenesmus (i.e., cramps in the rectum felt after a bowel movement), a feature suggesting the inflammation of rectum, is present in cases of shigellosis.

Physical:

Causes:

The most common causes are (1) leaving prepared food at temperatures that allow bacterial growth, (2) inadequate cooking or reheating, (3) cross-contamination, and (4) infection in food handlers. Cross-contamination may occur when raw contaminated food comes in contact with other foods, especially cooked foods, through direct contact or indirect contact on food preparation surfaces.

Bacteria are responsible for approximately two thirds of the outbreaks of food poisoning with a known cause in the United States. As many as 1 in 10 Americans has diarrhea due to food-borne infection each year.

Lab Studies:

Other labs including CBC count with differential, serum electrolyte assessment, and BUN and creatinine levels help to assess the inflammatory response and the degree of dehydration. Assay for C difficile should be done to help rule out antibiotic-associated diarrhea in patients receiving antibiotics or those with a history of recent antibiotic use.

Imaging and Other Studies:

Sigmoidoscopy should be considered in patients with bloody diarrhea. It can be useful in diagnosing inflammatory bowel disease, antibiotic-associated diarrhea, shigellosis, and amebic dysentery.

Treatment:

Some practical tips: At home oral rehydration is achieved by administering clear liquids and sodium-containing and glucose-containing solutions. A simple solution (ORS) may be composed of 1 level teaspoon of salt and 4 heaping teaspoons of sugar added to 1 liter of water. The use of ORS has reduced the mortality rate associated with cholera from higher than 50% to less than 1%. ORS also is indicated in other dehydrating diarrheal diseases. The World Health Organization (WHO) recommends a solution (under medical care) containing 3.5 g of sodium chloride, 2.5 g of sodium bicarbonate, 1.5 g of potassium chloride, and 20 g of glucose per liter of water. Intravenous solutions are indicated in patients who are severely dehydrated or who have intractable vomiting.

Absorbents (eg, Kaopectate, aluminum hydroxide) help patients have more control over the timing of defecation. However, they do not alter the course of the disease or reduce fluid loss. An interval of at least 1-2 hours should elapse when using other medications with absorbents. Antisecretory agents such as bismuth subsalicylate (Pepto- Bismol) may be useful. The dose is 30 mL every 30 minutes, not to exceed 8-10 doses a day. Antiperistaltics (opiate derivatives like Lomotil and Imodium) should not be used in patients with fever, systemic toxicity, or bloody diarrhea or in patients whose condition either shows no improvement or deteriorates.

If symptoms persist beyond 3-4 days, the specific etiology should be determined by performing stool cultures. If symptoms persist and the pathogen is isolated, specific treatment should be initiated. Once cultures are performed, empiric treatment with an agent that covers Shigella and Campylobacter organisms is reasonable in those with severe diarrhea with systemic signs. A 3-day course of a fluoroquinolone (eg, ciprofloxacin 500 mg twice a day, norfloxacin 400 mg twice a day) is the first-line therapy. TMP/SMX (Bactrim DS 1 tab once a day) is an alternative therapy, but resistant organisms are common in the tropics. Infection with either V cholerae or V parahaemolyticus can be treated with either a fluoroquinolone or with doxycycline (100 mg twice a day).

Deterrence/Prevention:

Local health authorities should be notified if an outbreak of food poisoning occurs. This leads to appropriate actions to prevent further spread of food poisoning. Irradiation of food (ie, the use of ionizing radiation or ionizing energy to treat foods, either packaged or in bulk form) can eliminate food-borne pathogens. Annually, more than half a million tons of food is now irradiated worldwide. Treating raw meat and poultry with irradiation at the slaughter plant could eliminate bacteria such as E coli O157:H7 and Salmonella and Campylobacterorganisms. No evidence of adverse health effects is found in the well-controlled clinical trials involving irradiated food.

Traveler's Diarrhea:

Complications:

Medical/Legal Concerns:

Immediate specific antibiotic therapy is not indicated in most food-borne illnesses; therefore, the physician should not be concerned about medicolegal pitfalls regarding failure to prescribe an antibiotic. In fact, in most cases of food poisoning, antibiotics are contraindicated. However, if the patient has bloody diarrhea with fecal leukocytes, then a stool culture and a search for ova and parasites should be undertaken, and empiric therapy with antibiotics instituted until the cause is determined, at which time the antibiotic might be changed for reasons of specificity.