US Pharm. 2012;37(12):50-53.
Foodborne illness poses a significant public health threat to the
United States. The CDC estimates that consumption of contaminated food
causes 48 million cases of illness each year, affecting approximately
15% of the population. Although the symptoms of foodborne illness are
often mild and self-limiting, severe cases account for about 128,000
hospitalizations and 3,000 deaths annually in the U.S.1 The
U.S. Department of Agriculture (USDA) estimates that the economic burden
of foodborne illness ranges from $10 billion to $83 billion annually, a
substantial impact.2 Media attention to outbreaks of
foodborne illness has increased in recent years, raising awareness—as
well as fear—in the American public. Television, Internet, and newspaper
coverage of outbreaks, such as the contaminated bagged spinach in 2006
and contaminated cantaloupe in 2011, has contributed to awareness of the
public health risk. Six deadly outbreaks were reported to the CDC from
2006 to 2011 (TABLE 1).3 In 2011, listeriosis
associated with cantaloupes from a farm in Colorado was linked to 30
deaths, one of the deadliest known outbreaks of foodborne illness in the
U.S.3
Foodborne illness, defined as any ailment associated with the
ingestion of contaminated food, is most often associated with
gastrointestinal symptoms, including diarrhea, nausea, and/or vomiting.4
Foodborne illness may be bacterial, viral, or parasitic in nature.
Although most ailments have acute symptoms that resolve within a week,
complications—including severe dehydration, bacteremia, renal and
hepatic impairment, neurologic symptoms, miscarriage, and surgical
complications—can occur.1,5
Risk Factors
Individuals who are aged less than 5 years or more than 60 years or
who are immunocompromised are at greatest risk for acquiring a foodborne
illness.5 Other risk factors for foodborne illness include
the consumption of high-risk foods such as unpasteurized milk and milk
products, unwashed fresh produce, and undercooked poultry, meat, and
eggs. Outbreak information from the CDC suggests that eating out also
increases the risk of contracting a foodborne illness. In 2008, 52% of
single-source outbreaks were linked to restaurants or delicatessens,
whereas only 15% were associated with eating at home.6 The use of proton pump inhibitors and histamine-2 antagonists also have been linked to foodborne illness.7
Trends
To track foodborne illness, the CDC, the USDA Food Safety and
Inspection Service, the FDA, and 10 state health departments
collaboratively collect information via the Foodborne Disease Active
Surveillance Network (FoodNet). FoodNet conducts active,
population-based surveillance for laboratory-confirmed cases of
foodborne illness isolated from the 10 participating states (California,
Colorado, Connecticut, Georgia, Maryland, Minnesota, New Mexico, New
York, Oregon, and Tennessee). Currently, the seven bacterial pathogens
tracked through FoodNet are Salmonella, Escherichia coli (E coli), Listeria, Campylobacter, Shigella, Yersinia, and Vibrio. Live, healthy animals are the source of most of these pathogens, with the exception of Shigella (intestines of an ill host) and Vibrio (marine waters and shellfish).1
According to the CDC, the incidence of five of the seven reportable foodborne bacterial pathogens (Campylobacter, Listeria, Shiga toxin–producing E coli (STEC) O157, Shigella, and Yersinia) decreased from 1996 to 2010 (TABLE 2).1 Salmonella incidence has not changed significantly over this time period. Vibrio infections are on the rise, although the overall incidence is quite low—0.4 illnesses per 100,000 people.1
Although the incidence of foodborne illness in general does not
appear to be significantly increasing, foodborne illness associated with
fresh produce is on the rise.8,9 The bacterial pathogens of greatest concern are Salmonella, E coli (mainly O157:H7), and Listeria monocytogenes (L monocytogenes).8 Of these pathogens, Salmonella is the most prevalent, causing illness in 17.6 of 100,000 persons. Salmonella accounted for 2,290 hospitalizations and 29 deaths in 2010, the highest of any foodborne pathogen.1 Listeria
infections increased greatly in 2011 as a result of the contaminated
cantaloupe outbreak, with 30 deaths linked to that outbreak alone.10
Although the incidence of listeriosis is low (0.3 cases per 100,000
persons), the hospitalization and case-fatality rates (90% and 12.8%,
respectively) are the highest of any bacterial pathogens associated with
foodborne illness.1,11 The incidence of another common pathogen, E coli O157,
has declined significantly in recent years, likely a result of
increased prevention efforts as well as improved detection and
investigation of outbreaks following the bagged spinach outbreak in
2006.1,12 The incidence of E coli O157 is now less than 1 per 100,000 persons, which meets the Healthy People 2010 goal for this organism.1 Despite this, E coli
O157 is still commonly linked to outbreaks of foodborne illness
involving both meat and produce and remains a significant public health
threat. E coli O157 is responsible for approximately 75% of enterohemorrhagic E coli infections worldwide and has an estimated hospitalization rate of 46.2% in the U.S.11,13
Bacterial Pathogens
Salmonella: Salmonella has traditionally been
linked to animal products, including poultry and eggs, although recently
it has caused many foodborne illnesses involving fresh fruits and
vegetables. Since 2006, Salmonella has been associated with foods
such as alfalfa sprouts, tomatoes, jalapeño peppers, black pepper,
papayas, cantaloupes, and various nuts.3 Salmonella is
spread via the fecal-oral route, commonly through contact with
contaminated water. There are two categories of salmonellosis:
nontyphoidal and typhoidal (caused by Salmonella typhi or Salmonella paratyphi). Salmonella
strains predominantly cause nontyphoidal salmonellosis in the U.S.
Symptoms (commonly diarrhea, nausea, vomiting, abdominal cramps,
headache, and fever) typically occur within 72 hours of exposure and
last for 4 to 7 days. Most cases are self-limiting, and the mortality
rate is less than 1%.14
Approximately 8% of patients with nontyphoidal salmonellosis will
develop bacteremia and require treatment with antibiotics, including
ceftriaxone or azithromycin in children and a fluoroquinolone (commonly
levofloxacin) or azithromycin in adults. Patients with nontyphoidal
salmonellosis and one or more risk factors for bacteremia should be
given antibiotics immediately. These risk factors include age under 3
months or over 65 years, corticosteroid use, inflammatory bowel disease,
immunosuppression, and hemodialysis. Antibiotics are recommended in
patients with a prosthetic heart valve or abdominal aneurysm to reduce
the risk of focal infection.15 Diarrheal ailments such as
salmonellosis are generally treated with rehydration therapy with oral
fluids (IV, if necessary), salt intake (commonly through soups and
crackers), and an easily digestible diet such as “BRAT” (bananas, rice,
applesauce, and toast) until symptoms resolve.15,16
E coli O157: E coli bacteria are an essential part of the intestinal flora of humans. E coli is usually harmless and, in fact, is protective to the host. However, strains of STEC, such as E coli O157, can cause serious, bloody diarrhea in the host.13 E coli
O157 is predominantly associated with undercooked beef and beef
products, although lately it has been more prevalent in fresh produce.
In recent years, E coli O157 contamination has occurred in foods such as spinach, romaine lettuce, hazelnuts, and clover sprouts.3 Waterborne outbreaks have been linked to bodies of fresh water, swimming pools, and ice.17
After exposure, hemorrhagic colitis often results within 48 hours.
Hemorrhagic colitis presents as severe abdominal cramping, nausea,
vomiting, and diarrhea that changes from watery to bloody.
Life-threatening complications of E coli O157 infections include hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenia purpura.13 HUS, which occurs when Shiga toxin is absorbed, thereby injuring glomerular cells, results in death in 3% to 5% of cases.13,15
Antibiotic therapy is thought to increase the risk of HUS, as is the
use of antimotility drugs (e.g., loperamide), which may slow the exit of
the enteropathogen from the body; these therapies therefore are not
recommended.15,16 Treatment should focus on rehydration and on reducing the risk of severe complications.
L monocytogenes: L monocytogenes is another pathogen that can contaminate foods and cause foodborne illness. Unlike many other pathogens, L monocytogenes can live and grow in refrigeration temperatures and salty environments.18 L monocytogenes
contamination has been associated with unpasteurized milk and milk
products (e.g., soft cheeses), meats (especially deli meats), hot dogs,
raw produce, and seafood. The incidence of L monocytogenes
contamination is low, but the fatality rate is high. Pregnant women are
at greater risk for listeriosis. Although frequently the mother has mild
symptoms, the risks to the fetus are severe. There is a 1-in-3 chance
of spontaneous abortion or stillbirth, as well as an increased risk of
bacteremia or meningitis in the neonate.19
Listeriosis usually occurs within 3 days after exposure and in less
severe cases lasts from days to weeks; symptoms are consistent with a
diarrheal ailment. More severe cases may last for several months and can
cause complications such as septicemia and meningitis.19 The
treatment of choice for complicated listeriosis is ampicillin
(trimethoprim-sulfamethoxazole, in the case of penicillin allergy), with
or without gentamicin, for 3 to 6 weeks.20 As with all foodborne illnesses in which diarrhea is present, rehydration therapy is vital.
Prevention
The key to reducing the incidence of foodborne illness is prevention.
Proper food storage, refrigeration, handling, and cooking are vital.
Patients should be educated to avoid high-risk items such as
unpasteurized milk and milk products, as well as raw or undercooked
items like oysters, meat, poultry, and eggs. The consumption of more
meals in the home may also decrease the risk of foodborne illness.6
According to food-safety experts, two important steps should be
implemented in the home to reduce the risk of foodborne illness: washing
the hands thoroughly when handling food, and using a thermometer to
ensure that adequate food temperatures (TABLE 3) are reached during cooking.21,22
Steps to reduce cross-contamination should also be implemented,
including using a separate cutting board and utensils for raw and fresh
foods and frequently disinfecting kitchen surfaces. To prevent the
spread of bacteria harbored by kitchen towels and sponges, paper towels
should be used to clean up cooking spills, and kitchen towels should be
laundered frequently. To significantly reduce bacteria, kitchen sponges
may be placed in the dishwasher for a heated cycle or microwaved while
wet for 1 minute.23 Some evidence suggests that reusable
shopping bags also may harbor bacteria, so separate bags should be used
for fresh produce and meat. Also, washing the bags thoroughly either by
hand or in the washing machine may help reduce the spread of bacteria to
foods.24 Using caution to prevent the spread of bacteria is essential to the reduction of foodborne illness.
A four-step approach to improving food safety, as recommended by the
Partnership for Food Safety Education (PFSE), is described in TABLE 4.25
For fresh produce, the PFSE recommends two additional steps. First, be
sure that produce is not damaged or bruised and is adequately
refrigerated, if precut. Additionally, throw away produce that has been
compromised by bruises or improper storage or that may have been in
contact with raw meat, poultry, or seafood. When it comes to the safety
of fresh produce, the PFSE recommends: “If in doubt, throw it out.”26
Conclusion: Pharmacists’ Role
Pharmacists can help identify individuals who may be at high risk for
foodborne illness, educate patients about how to prevent foodborne
illness, make recommendations for self-care, and report incidences of
foodborne illness to the local health department and the CDC. Elderly
patients, those with small children, and those who are immunocompromised
would benefit from education about how to prevent foodborne illness.
Pregnant patients should be advised to avoid consuming foods that may be
contaminated with Listeria (e.g., deli meats, undercooked meats
and hot dogs, unpasteurized milk and soft cheeses, and unwashed fresh
produce), particularly because of the risk of harm to the fetus. The CDC
and other government agencies maintain Web sites that provide a wealth
of valuable food safety information for consumers. Some examples include
the PFSE (http://fightbac.org), FoodSafety.gov (http://foodsafety.gov),
and Food Safety for Moms-to-Be
(www.fda.gov/Food/ResourcesForYou/HealthEducators/ucm081785.htm).
To report a suspected or confirmed foodborne illness, pharmacists can
visit www.cdc.gov/outbreaknet/reportillness.html or call 1-800-CDC-INFO
(1-800-232-4636). Illness data are used to determine where and why
outbreaks occur and may be used to inform the public of the suspected
contaminated source. Not all illnesses are associated with large
outbreaks; trends can occur on a smaller scale, associated with
individual restaurants or foods. The tracking of foodborne illness is
essential to our understanding of how these illnesses occur and how
future outbreaks can be prevented.
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