Harwood-Nuss' Clinical Practice of Emergency Medicine, 6 ed.

CHAPTER 195
Food Poisoning

Marc C. Restuccia

The Centers for Disease Control (CDC) estimates that roughly 1 in 6 Americans (48 million) become ill, 128,000 are hospitalized and 3,000 die of foodborne illnesses each year (1). This number is an improvement over previous estimates published by CDC of 76 million made ill, 323,000 hospitalized and 5,000 annual deaths (2). Despite these improvements, foodborne illness remains a serious public health problem. Even as advances have been made in decreasing the incidence of certain foodborne illnesses, the incidence of others has either remained the same or worsened somewhat (3). In 1996, the CDC established the Foodborne Diseases Active Surveillance Network, known as FoodNet. This easily accessible resource tracks foodborne illnesses as well as monitors efforts to enhance food safety.

Food can be contaminated during all stages of production. “Modern” industrial sized farms and centralized; worldwide distribution systems create opportunities for amplification of any breakdown in food safety systems. Food can be contaminated with bacteria, viruses, parasites, toxins, and the relatively newly described prions.

For most people suffering from foodborne illness, it is a self-limited process with nausea, vomiting, abdominal pain, and diarrhea. In other patients, however, it can present with neurologic symptoms, hepatic failure, or renal failure. As in many disease processes, the young, the old, and the immunocompromised are at greater risk for significant sequelae. The clinician must also be wary of other, often more serious illnesses, which can be mistaken for food poisoning. Individual cases of foodborne illness are virtually impossible to diagnose with any certainty, overlapping with nonfoodborne gastrointestinal infections. The diagnosis is most typically entertained and confirmed when multiple persons become ill and the etiology can be traced to a specific event and/or food.

CLINICAL PRESENTATION

Alteration of normal gastrointestinal tract function is the most typical presentation for a patient with a foodborne illness. Nausea, vomiting, diarrhea, abdominal pain, and fever are the most common complaints. However exceptions exist; botulism, caused by the botulinum toxin, classically seen in infants consuming raw honey (4), presents with a progressive paralysis. Other manifestations of foodborne illness can include neurologic symptoms (seen with Scombroid and Ciguatera fish poisoning as well as mushrooms) as well as systemic illness including fever, weakness, jaundice, and arthritis (seen with Salmonella, Toxoplasma, and Trichinella poisoning) (5). Abdominal pain is a frequent complaint in patients with a foodborne illness and it can be difficult to differentiate the cause from other conditions such as appendicitis.

Diarrhea can be watery or bloody. This may be helpful in narrowing down the diagnostic possibilities. Although the presence of watery diarrhea is fairly nonspecific, bloody diarrhea implies an enteroinvasive diarrhea, with the most common cause being Escherichia coli 0157-H7 and Salmonella. Campylobacter less commonly causes bloody diarrhea (6).

With progression of the illness, dehydration may develop. Thirst, dry mucous membranes and eventually tachycardia with hypotension can be seen, especially in acutely ill children or the elderly. Altered mental status more commonly affects in the young and elderly. Table 195.1 lists the major manifestations associated with the more common pathogenic organisms.

TABLE 195.1

Bacterial Causes of Food Poisoning

DIFFERENTIAL DIAGNOSIS

The diagnosis of foodborne illness is typically made on clinical grounds. The Physical examination, although important in assessing the volume status of the patient, typically does not distinguish the cause of nausea, vomiting, abdominal pain, fever, and/or diarrhea. As is noted in Table 195.1, the incubation period for many of these illnesses is measured in hours, if not days. A history of recent meals, especially meals where other individuals may have shared foods and time of ingestion may be helpful to determine the source.

Toxin-producing pathogens such as enterotoxigenic E. coli, Staphylococcus aureus, and Vibrio cholerae often cause profuse watery diarrhea. Symptoms begin within hours of ingesting contaminated foods. By way of contrast, organisms such as Cryptosporidium cyclospora and Giardia also lead to a watery diarrhea, typically days to weeks after ingestion. Hikers and campers who drink unfiltered or untreated back-country water are at risk of developing painful abdominal cramping, profuse watery diarrhea, and flatulence from Giardia infection.

Invasive organisms such as nonenterotoxigenic E. coli, Campylobacter, Shigella, Yersinia, and Vibrio infect the cells lining the intestinal tract and cause a bloody diarrhea that typically begins within 24 hours of ingestion. The stools of such patients will typically have both occult blood and fecal leukocytes (8). The parasite, Entamoeba histolytica can also cause bloody diarrhea. Clostridium difficile, which colonizes the human gastrointestinal tract after the normal flora has been suppressed by wide-spectrum antibiotics, releases toxins which lead to a profuse bloody diarrhea. Although not a foodborne illness, with increased use of wide-spectrum antibiotics, it is an increasingly and difficult to treat condition causing diarrhea, abdominal pain, vomiting, and fever.

Viral infections are the leading cause of nausea, vomiting, and diarrhea. Rotavirus is an illness of young children during the winter months. Norovirus, Hepatitis A, and Parvovirus show no seasonal predilection. Typically vomiting is more prominent in viral gastroenteritis and toxin-related foodborne illness than in other types of gastroenteritis resulting from bacterial or parasitic infections. Characteristics of the history that are consistent with a viral etiology include an incubation period of 20 to 60 hours, a duration of 12 to 60 hours and a high frequency of vomiting (9).

Contamination of food with pesticides or other chemicals during growth, harvesting, or processing can also lead to foodborne illnesses (10,11).

Other conditions that must be considered in the differential diagnosis of anyone presenting to the emergency department (ED) with nausea, vomiting, fever, and abdominal pain include biliary tract disease, peptic ulcer disease, coronary artery disease, appendicitis, intussusception, volvulus, diverticulitis, inflammatory bowel disease as well as poisoning by heavy metals, mushrooms, and seafood toxicity.

ED EVALUATION

The history should focus on recent meals, within 24 to 48 hours prior to presentation. Key questions include what was consumed, how it was prepared, how was it stored after preparation, and whether or not anyone else is ill who consumed the same food. The time of onset, nature, and progression of the illness, particularly the character of the diarrhea should be noted. Patients should be asked about travel, especially to regions with a high incidence of foodborne illness such as Mexico. Any recent use of antibiotics should be ascertained. For patients who are hikers or campers, questions about drinking unfiltered or untreated water in the recent past should be sought. Underlying medical conditions, especially those that may lead to immunodeficiency such as diabetes, or malignancies should be determined. Other significant medical conditions such as coronary artery disease should be identified and noted.

The physical examination should focus on the hydration status of the patient and a general physical examination, with particular attention to the abdomen. Serial examinations including vital signs, allow the treating clinician to rapidly identify and deterioration of the patient’s condition. Laboratory testing may rarely assist in identifying the cause of a foodborne illness. Routine blood tests are usually not indicated. The CDC does recommend blood testing for patients with bloody diarrhea, weight loss, dehydration, fever, prolonged diarrhea (three or more unformed stools per day for several days), neurologic involvement (such as paresthesias, other weakness or cranial nerve palsies), sudden onset of symptoms, or severe abdominal pain (5). Laboratory testing is also recommended for the young and old and in those patients with comorbid conditions or immunosuppression. In these cases, a complete blood count, basic metabolic panel (electrolytes, BUN, creatinine, glucose), and a urinalysis are reasonable. Blood cultures have long been recommended for patients suspected of bacteremia, however recent literature calls this into question (12). Patients with significant abdominal pain, suspicious for a surgical etiology should have either a screening upright CXR bedside ultrasound or abdominal CT as indicated on the basis of their presentation. A screening ECG is indicated if any concern is raised about the potential for an acute myocardial infarct presenting with GI symptoms. This is especially true for women and the elderly.

Patients with severe abdominal pain and bloody diarrhea should have their stool checked for fecal leukocytes. C. difficile stool toxin assays should be ordered on patients with a history of recent antibiotic use.

Stool cultures are indicated for immunocompromised or febrile patients with bloody diarrhea, presence of fecal leukocytes or severe, protracted illness. Laboratory protocols and procedures can differ between facilities. Many laboratories are limited to testing for Salmonella, Shigella, and Campylobacter species. If Vibrio, Yersinia, or E. coli O157:H7 are suspected, special collection and handling are usually necessary. Consultation with the hospital’s microbiology laboratory is important to ensure proper collection and handling of specimens. Stool should be examined for parasites if the patient has a suggestive travel history, is immunocompromised or has persistent diarrhea.

KEY TESTING

• Routine (most patients): Electrolytes, HCG

• Bloody diarrhea: Fecal leukocytes/occult blood

• CBC, consider blood cultures

• Titer for C. difficile

• Immunocompromised: CBC, blood cultures

• Surgical abdomen: Upright chest x-ray

• Bedside ultrasound

• Abdominal/pelvic CT scan

• Preoperative laboratories

• Travel: Stool for ova and parasites

• Concern for an MI: ECG

• Bloody stools/Immunocompromised: Stool culture

ED MANAGEMENT

The first priority for any patient presenting to the ED with nausea, vomiting, diarrhea, abdominal pain, and fever is adequate volume resuscitation. In many patients this can be accomplished with oral rehydration. Some patients however will not be able to tolerate oral hydration and will have to be resuscitated intravenously. Fluid boluses if needed to establish an age normal mean blood pressure, followed by maintenance infusions should be initiated. Antiemetics such as ondansetron or metoclopramide may be helpful, especially if oral hydration is being attempted. Anti-diarrheal medications are now accepted as routine therapy for patients with traveler’s diarrhea, typically caused by strains of E. coli. However, such medications should not be given to patients with bloody diarrhea as it is thought that their use can prolong symptoms or lead to more serious complications.

Antibiotics are indicated in only a small number of foodborne illnesses. Diarrhea due to viruses and most bacteria does not improve more rapidly with antibiotics and can actually worsen. However, antibiotics may be appropriate in patients who are septic, immunosuppressed, the elderly, or have serious comorbid conditions. Table 195.1 contains recommendations for when antibiotics are appropriate therapy.

The CDC requires notification of state and/or local public health departments for certain foodborne illnesses. Prompt notification of the appropriate local department of public health enables authorities to determine the best course of action to limit the outbreak. Having a centralized repository for such information allows for earlier recognition of a widespread outbreak of a foodborne illness. Such syndromic surveillance is vital in today’s environment where not only “natural” but terrorist threats to the food supply cannot be discounted. When more than a few cases of presumed foodborne illness are identified, rapid identification of the type and source of the foodborne disease will limit the effects on a population.

CRITICAL INTERVENTIONS

• Rapidly provide adequate resuscitation to patients in hypovolemic shock from dehydration.

• Avoid early diagnostic closure; keep the possibility of more serious sequelae/disease processes in mind.

• Notify appropriate public health officials of potential foodborne illnesses, especially if multiple patients are identified.

DISPOSITION

Most patients can be safely discharged home after being rehydrated and demonstrating their ability to keep oral intake down. Discharge instructions should include maintaining a generous intake of fluid and beginning frequent small meals of solid food as soon as tolerated. Patients should be educated on signs and symptoms of dehydration, such as monitoring their urinary output. They should further be advised to return to the ED if symptoms recur, if they are unable to tolerate oral intake, or if they develop a fever or abdominal pain.

Patients with suspected bacteremia or who do not improve with standard therapy should be admitted to the hospital. Nonbacteremic patients may be suitable for observation status. Patients at the extremes of age, underlying comorbid conditions will usually need to be admitted. If the diagnosis is unclear and symptoms continue, admission will be necessary for further evaluation.

Common Pitfalls

• Failure to consider foodborne illness in all patients with nausea, vomiting, diarrhea, abdominal pain, and/or fever.

• Failure to obtain a history of antecedent antibiotic use, travel, camping or hiking, and diet specifics.

• Failure to consider other diagnoses such as appendicitis, aortic aneurysm, pyelonephritis, cholecystitis, pneumonia, pregnancy, or myocardial infarction.

• Failure to consider the effects of comorbid diseases in the management of patient with foodborne illness.

• Discharging patients who cannot take oral fluids, especially if they have not been adequately resuscitated.

• Failure to notify public health authorities when treating a patient with suspected or confirmed foodborne illness.

REFERENCES

 1. Centers for Disease Control and Prevention. Vital signs: Incidence and trends of infection with pathogens transmitted commonly through food–foodborne diseases active surveillance network, 10 U.S. Sites, 1996–2010. MMWR Morb Mortal Wkly Rep. 2011;60(22):749–755.

 2. Centers for Disease Control and Prevention. Trends in Foodborne Illness in the United States, 1996–2012. http://www.cdc.gov/foodborneburden. Accessed February 6, 2013.

 3. Centers for Disease Control and Prevention. Trends in Foodborne Illness in the United States. http://www.cdc.gov/fodborneburden/trends-in-foodborne-illness.html. Accessed April 22, 2013.

 4. Pigott D. Foodborne illness. Emerg Med Clin North Am. 2008;26:475–497.

 5. Centers for Disease Control and Prevention. Diagnosis and management of foodborne illness, a primer for physicians and other health care professionals. MMWR Morb Mortal Wkly Rep. 2004;53(RR-4):1–33.

 6. Slutsker L, Ries AA, Greene KD, et al. Escherichia coli O157-H7 diarrhea in the United States, clinical and epidemiological features. Ann Intern Med. 1997;126:505–513.

 7. Guerrant RL, Van Gilder T, Steiner TS, et al. Practical guidelines for the management of infectious diarrhea. Clin Infect Dis. 2001;32:331–351.

 8. Huicho L, Sanchez D, Contreras M, et al. Occult blood and fecal leukocytes as screening tests in childhood infectious diarrhea; An old problem revisited. Pediatr Infect Dis J. 1993;12:474–477.

 9. Kaplan JE, Feldman R, Campbell DS, et al. The Frequency of a Norwalk like pattern of illness in outbreaks of acute gastroenteritis. Am J Public Health. 1982;72:1329–1332.

10. Wolkin AF, Martin CA, Law RK, et al. Using poison center data for national public health surveillance for chemical and poison exposure and associated illness. Ann Emerg Med. 2012;59(1):56–61.

11. Rangan C, Barceloux DG. Food contamination. Medical Toxicology of Natural Substances: Food, Fungi, Medicinal Herbs, Toxic Plants and Venomous Animals. Hoboken, NJ: John Wiley and Sons; 2008:P5–P21.

12. Hom J. Is there a blood test that can rule out serious bacterial infection in children? Ann Emerg Med. 2012;60(1):92–93.



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