Foodborne Illness

Paras Patel

James W. Myers

INTRODUCTION

According to a report from the Centers of Disease Control and Prevention, foodborne illnesses account for approximately 76 million illnesses, leading to 325,000 hospitalizations and 5,000 deaths each year in the United States.

Diarrheal diseases represent one of the five leading causes of death worldwide. Morbidity and mortality are significant even in the United States, where diarrhea is more often than not a “nuisance disease” in the normally healthy individual.

DEFINITIONS

Clinically, diarrhea is defined as stool weight in excess of 200 g/day or more than or equal to three loose or watery stools per day, or a definite decrease in consistency and increase in frequency based upon an individual baseline.
Diarrhea reflects increased water content of the stool, whether due to impaired water absorption and/or active water secretion by the bowel.
In severe infectious diarrhea, the number of stools may reach 20 or more per day, with defecation occurring every 20 or 30 minutes. In this situation, the total daily volume of stool may exceed 2 L, with resultant volume depletion and hypokalemia.
Most patients with acute diarrhea have three to seven movements per day with total stool volume <1 L/day.
When diarrhea lasts for 14 days, it can be considered persistent; the term chronic generally refers to diarrhea that lasts for at least 1 month.

The following definitions have been suggested according to the duration of diarrhea (Table 49-1).

PATHOGENIC MECHANISMS IN FOODBORNE ILLNESS

The following divides foodborne diseases into a variety of syndromes, mostly based on signs and symptoms and time of onset after consumption of contaminated food, and indicates the agents most likely responsible for the illness (Table 49-2).
If the pathogen makes the toxin before the food is eaten, the onset of symptoms will be sooner, around 6 hours, and primarily be vomiting or other upper intestinal in nature.
On the other hand, if the toxin is made after ingestion, the symptoms will take longer, around 24 hours, and be more of a watery diarrhea illness.
Pathogens that damage or invade tissue are often associated with fever and systemic illness, but a variety of symptoms are possible.

Table 49-1 Definitions of Diarrhea

Entity	Days	Comment
Diarrhea		Diarrhea is defined as stool weight in excess of 200 g/day
Acute	<14
Persistent	>14
Chronic	>30
Severe		The number of stools may reach 20 or more per day, with defecation occurring every 20 or 30 minutes. In this situation, the total daily volume of stool may exceed 2 L, with resultant volume depletion and hypokalemia.

FOODBORNE DISEASE SYNDROMES

Most cases of acute diarrhea are due to infections with viruses and bacteria and are self-limited.
Noninfectious etiologies become more common as the course of the diarrhea persists and becomes chronic.

The evaluation of patients for a noninfectious etiology should be considered in those patients in whom evaluation fails to identify a pathogen (e.g., bacterial, viral, or protozoal) and the diarrhea worsens or becomes chronic.

TABLE 49-2 Major Pathogenic Mechanisms in Some Foodborne Illness

Preformed Bacterial Toxin	Toxin Production In Vivo	Tissue Invasion	Seafood Toxins
Staphylococcus aureus	Clostridium perfringens	Campylobacter jejuni	Ciguatera
Bacillus cereus^a	Shiga toxin-producing E. coli	Salmonella	Paralytic shellfish poisoning
Clostridium botulinum	C. botulinum	Shigella	Scombroid
	Enterotoxigenic E. coli	Invasive E. coli	Poisonous mushrooms
	Vibrio cholerae O1 or O139	Listeria monocytogenes
	Clostridium difficile	Yersinia enterocolitica?
	V. cholerae non-O1	Norovirus?
		Cryptosporidium, Cyclospora, Giardia?
^aAlso has a long incubation form with toxin production in vivo.

Foodborne disease can appear as an isolated sporadic case or, less frequently, as an outbreak of illnesses affecting a group of people after a common food exposure.
- The diagnosis of foodborne disease should be considered when an acute illness, especially one with gastrointestinal or neurologic manifestations, affects two or more people who had shared a common meal.
- Important clues to the etiologic agent are provided by the signs and symptoms of affected persons and the incubation period.
- The incubation period in an individual illness is usually unknown, but it is often apparent in the focal outbreak setting.
Tables 49-3 and 49-4 divide foodborne diseases into a variety of syndromes, mostly based on signs and symptoms and time of onset after consumption of contaminated food, and indicate the agents most likely responsible for the illness see Table 49-5 for a comparison of common foodborne illnesses.

TREATMENT

Often, the most important measures are general ones such as hydration and alteration of diet.
Antibiotic therapy is not required in most cases.
The treatment of specific infections is listed in Tables 49-6 and 49-7.
Antimotility agents can occasionally be helpful:
- Loperamide is useful in those patients in whom fever is absent or low grade and the stools are not bloody.
- In two randomized controlled studies, loperamide compared with placebo significantly decreased the number of liquid bowel movements or diarrhea when given with ciprofloxacin. The dose of loperamide is two tablets (4 mg) initially, then 2 mg after each unformed stool, not to exceed 16 mg/day for ≤2 days.
- Diphenoxylate (Lomotil) is an alternative agent, but it has not been studied in randomized controlled studies.
- The dose of diphenoxylate is two tablets (4 mg) four times daily for ≤2 days. Diphenoxylate has central opiate effects and may cause cholinergic side effects.
- Note that both drugs can precipitate the development of the hemolytic uremic syndrome (HUS) in patients infected with Enterohemorrhagic E. coli (EHEC).
Bismuth subsalicylate (Pepto-Bismol) has also been used for symptomatic treatment of acute diarrhea.
- When compared with placebo, bismuth subsalicylate significantly reduced the number of unformed stools and increased the proportion of patients free of symptoms at the end of treatment trials.
- However, in studies that compared bismuth subsalicylate with loperamide, loperamide brought significantly faster relief.
- A role for bismuth subsalicylate may be in patients with significant fever and dysentery, conditions in which loperamide should be avoided.
- The dose of bismuth subsalicylate is 30 mL or two tablets every 30 minutes for eight doses.
Probiotics, including bacteria that assist in recolonizing the intestine with nonpathogenic flora, can also be used as alternative therapy.

Probiotics have been shown to be useful in treating traveler’s diarrhea and acute nonspecific diarrhea in children.

Table 49-3 Infectious Syndromes

Syndrome	Etiology	Pathogenesis	Clinical Features	Associated Foods
Nausea and vomiting within 1-6 hours	S. aureus, B. cereus^a	Preformed enterotoxins, heat-resistant toxins; food may not smell or look bad.	Severe nausea and vomiting, very little fever with Staph., short duration of illness (12-24 hours); patients with this illness are not contagious. Toxins are not transmitted from one person to another. Supportive care	S. aureus: unrefrigerated meats, potato, or egg salad, cream-filled pastries B. cereus: fried rice, meats, vegetables
Abdominal cramps and diarrhea within 8-16 hours	C. perfringens and B. cereus	Enterotoxin mediated; toxin is not preformed.	Watery diarrhea, nausea, abdominal cramps. Vomiting is NOT a major feature in these illnesses.	Meats, poultry, gravy, time- or temperatureabused food
Fever, abdominal cramps, and diarrhea within 6-48 hours	C. jejuni, E. coli, Salmonella, Shigella, and Vibrio parahaemolyticus.	Tissue invasion	Diarrhea, fever, abdominal cramps, vomiting	Contaminated eggs, poultry, unpasteurized milk or juice, contaminated water
Abdominal cramps and watery diarrhea within 16-72 hours	Enterotoxigenic strains of E. coli (ETEC), V. parahaemolyticus, V. cholerae non-O1, and, in endemic areas, V. cholerae O1 and O139; C. jejuni, Salmonella, and Shigella	Enterotoxins	Watery diarrhea, abdominal cramps, nausea, and vomiting	Water or food contaminated with human feces, undercooked or raw seafood such as fish, shellfish
Vomiting and nonbloody diarrhea within 24-48 hours	Noroviruses^b	Tissue invasion	Vomiting, diarrhea, abdominal pain, and nausea; fever occurs in one-third to one-half of patients, is usually low grade, and lasts for <24 hours. Cruise ships; aerosol transmission is possible. Very contagious, low infectious dose, no lasting immunity	Salads, shellfish
Fever and abdominal cramps within 16-48 hours, without diarrhea	Y. enterocolitica	Tissue invasion	May closely resemble acute appendicitis in older children and adults. Nausea and vomiting are relatively uncommon, occurring in <25%-40% of the cases. Illness can last up to 4 weeks.	Milk, pork, chitterlings
Bloody diarrhea without fever within 72-120 hours	E. coli most often serotype O157:H7	Shiga toxin or verotoxins	Severe diarrhea, often bloody, abdominal pain, and vomiting, little or no fever	Undercooked beef, especially hamburger; unpasteurized milk and juice; raw fruits and vegetables
Nausea, vomiting, diarrhea, and paralysis within 18-36 hours	C. botulinum	Heat-labile protein neurotoxins	Vomiting, diarrhea, blurred vision, diplopia, dysphagia, and descending muscle weakness	Home-canned foods with low acid content, improperly canned commercial foods
Persistent diarrhea within 1-3 weeks	Cyclosporiasis, cryptosporidiosis, giardiasis, and Brainerd diarrhea	Tissue invasion	Watery diarrhea, anorexia, weight loss, abdominal cramps, nausea, and body aches; vomiting and low-grade fever may be noted.	Contaminated water and food, milk
^aFood handler contaminates it and leaves the food at room temperature. Vomitus or food can be tested for toxin if necessary for Bacillus or Staphylococcus. ^bRT-PCR useful for diagnosis.