Foodborne Illness

Outbreaks point to the continued need for prevention.

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Learning Scope #419
1 contact hour
Expires Feb. 4, 2015

You can earn 1 contact hour of continuing education credit in three ways: 1) Grade and certificate are available immediately after taking the online test. 2) Send the answer sheet (or a photocopy) to ADVANCE for Nurses, Learning Scope, 2900 Horizon Dr., King of Prussia, PA 19406. 3) Fax the answer sheet to 610-278-1426. If faxing or mailing, allow 30 days to receive certificate or notice of failure. A certificate of credit will be awarded to participants who achieve a passing grade of 70 percent or better.

Merion Matters is an approved provider of continuing nursing education by the Pennsylvania State Nurses Association (No. 221-3-O-09), an accredited approver by the American Nurses Credentialing Center's Commission on Accreditation.

Merion Matters is also approved as a provider by the California Board of Registered Nursing (No. 13230) and by the Florida Board of Nursing (No. 3298).

The goal of this continuing education offering is to provide the latest information to nurses about foodborne illness. After reading this article, you will be able to:

1. Describe the health risk of food, soil and water pathogens that cause foodborne illnesses.

2. Discuss the pathogenesis of the primary foodborne organisms.

3. Provide potential resources for prevention and treatment of foodborne illnesses.

  • The author has completed a disclosure form and reports no relationships relevant to the content of this article.

As of 2011, 31 major pathogens acquired in the U.S. were estimated to cause 9.4 million episodes of foodborne illness, or more commonly termed, food poisoning. The related cost of the illnesses is staggering and very likely underestimated at $152 billion a year in the U.S. These illnesses plague our society and often lead to multifaceted long-term diseases and death. At best, they cause minor gastrointestinal problems, lost school and work days, with numerous emergency room, clinic and physician office visits connected to these illnesses.

Although raw numbers of infections reported are lower than in recent years, the CDC caution that identification and reporting systems have improved, yet the food supply may be no safer. For instance, reports of Escherichia coli- and Listeria-contaminated foods are down, but Salmonella contaminations are on the rise. The CDC also indicates that for every case of Salmonella reported, there are upward of 29 uncounted cases.

Since 1973, the CDC has maintained a collaborative, passive surveillance program for collection and reporting of data on foodborne disease outbreaks investigated by health departments. For surveillance purposes, a foodborne outbreak is defined as two or more cases of similar illness resulting from the ingestion of a common food. Food safety laws enforced by the FDA and the Food Safety Modernization Act (FSMA) of 2011 are but two regulatory mechanisms to assist in tracking foodborne pathogens, contamination and outbreaks, and set minimal standards for consumer food products. The FDA intends to mandate food recalls, specify the frequency of food safety inspections, require more inspections of foreign food handling facilities, and direct training to state, local, territorial and tribal food safety officials.

Serious Health Concerns

Common causes of foodborne illnesses emanate from contamination of a variety of bacteria, viruses, parasites, chemicals and by non-food mechanisms (contact with unwashed hands, animals or consumption of contaminated water). We must be concerned with the safety of growing, handling, preparing and storing food; keeping drinking water and soil safe; and educating the public about foodborne pathogens, prevention and treatment.

A variety of soil-related bacterial and fungal pathogens cause serious human disease that frequently present in primary care and emergency department settings. Typically, the growth of these microorganisms is favored by particular soil characteristics (moisture, sunlight, solids, gases, etc.) and may involve complex lifecycles, including amoebae or animal hosts. Specific organisms that evolved ability to grow in diverse, sometimes harsh, microenvironments may promote pathogenesis. Pathogenic fungi or bacteria may enter humans via direct contamination into cuts or wounds. Soil minerals to change the pH and promote crop growth introduced simultaneously may promote infection by suppressing local host defenses. Microorganisms may be introduced by bioaerosols (dusts or mud particles from soil disturbances, windblown spores) or by direct ingestion of soil or indirect ingestion via contaminated food.

Water-related gastrointestinal infections (Escherichia coli, Cryptosporidium, Campylobacter) often appear as area outbreaks rather than individual infections. Water supply can be public or private, fully treated or untouched from wells. In areas where water is treated with chlorination, less physician visits are made for foodborne illnesses. This is of significant socioeconomic, civil engineering importance since the major treatment of drinking water in the U.S. is with the additive antimicrobial chlorine.

Private wells, once thought to be significant sources of contaminants, actually contain less pathogens, perhaps due to increased vigilance of well owners and local officials to frequently test drinking and bathing household water supply. Public water and sewage systems often are piped in close proximity leading to potential cross-contamination through damage and leaks. Areas across the U.S. where these systems are old and in ill repair give rise to more frequent physician and hospital visits for food/water contamination. These municipal sewer systems may require more scrutiny than previously thought.

Each weekday millions of American students eat meals prepared and served at preschool, school and college. Among outbreaks in the student population of foodborne illness with a known etiology, Salmonella was the most commonly identified pathogen (Escherichia coli and Campylobacter also found). The foods with the highest levels of pathogens included meat, poultry, salads, cheeses, milk and Mexican dishes. The majority of outbreaks with known vehicles were caused by foods prepared on school premises; therefore, prevention efforts need focus on school-based interventions.

Practices identified as contributing to outbreaks in schools include improper refrigeration, prolonged handling and inadequate reheating of cooked foods. The risk of outbreaks caused by bacterial and parasitic pathogens could be further reduced through the broader application of irradiation pasteurization of solid foods using low-dose gamma rays, radiographs or electron beams. Recent research indicates that these pasteurization and irradiation practices are not universal and are often cost-prohibitive to farmers where food is grown or to smaller processing plants.

Major Pathogens

Salmonella (gram negative, non-spore-forming bacterial rods) causes salmonellosis by eating food contaminated with one of the major forms of Salmonella (Salmonella serotype typhimurium and Salmonella serotype enteritidis). Every year, approximately 40,000 cases of salmonellosis are reported in the U.S. More people are hospitalized with Salmonella poisoning each year than with any other single pathogen. Many milder cases are not diagnosed or reported, so the actual number of infections may be 30 or more times greater. This illness is more common in the summer than in the winter with children as the most likely targets. Young children, older adults and people with impaired immune systems are at the highest risk for severe infections, possibly necessitating hospitalization.

Symptoms of salmonellosis that develop 12-72 hours following ingestion include diarrhea, fever and abdominal cramps. The illness usually lasts 4-7 days. Most people recover without treatment, but diarrhea and dehydration may be so severe in any population that it is necessary to go to the hospital. A small number of people may develop Reiter's syndrome (a form of arthritis) following recovery of this acute infection.

Infection with Salmonella can happen in the following ways:

• Contamination during food processing or food handling.

• Contamination by the unwashed hands of an infected food handler.

• Contamination following handling of animal feces containing Salmonella: in particular, reptiles, baby chicks and ducklings, and small rodents (e.g., hamsters). Adults and children always should wash their hands immediately after handling one of these animals, even if the animal is healthy.

• Beef (e.g., ground meat), poultry, milk, eggs, nuts (e.g., peanut butter), fruits (e.g., cantaloupe) and vegetables are most often infected with Salmonella. Contaminated foods usually look and smell normal. The increase in association of outbreaks with fresh produce suggests some Salmonella now are evolved to attach to and colonize vegetables.

Escherichia coli (E. coli) bacteria normally live in the intestines of people and animals. Most E. coli are harmless and actually are an important part of a healthy human intestinal tract. However, some E. coli are pathogenic, causing either diarrhea or illness outside of the intestinal tract. The types of E. coli that can cause diarrhea can be transmitted through contaminated water or food, or through contact with animals or people, often through contact with feces.

E. coli consists of a diverse group of bacteria. Pathogenic E. coli strains are categorized into pathotypes. Six pathotypes are associated with diarrhea and collectively are referred to as diarrheagenic E. coli. Of the six, the Shiga-toxin strain is the most detrimental to humans.

Shiga toxin-producing E. coli (STEC) also may be referred to as verocytotoxin-producing E. coli (VTEC) or enterohemorrhagic E. coli (EHEC). This pathotype is the one most frequently heard about in the news in association with foodborne outbreaks. The most commonly identified STEC in North America is E. coli O157:H7. Young children tend to carry STEC longer than adults, so feces may be affected for weeks or longer.

Campylobacteriosis is an infection by Campylobacter (especially C. Jejuni). The common routes of transmission are fecal-oral cross-contamination, ingestion of contaminated food or water and eating raw meat or poultry. Meat and poultry juices can be picked up by food preparation surfaces into previously non-contaminated food, thereby causing potentially dangerous cross-contamination of safe food. It produces an inflammatory, sometimes bloody diarrhea, periodontitis and dysentery syndrome, including cramps, fever and pain. Camphlobacter invasion generally stays within the gastrointestinal tract. The infection is usually self-limiting and, in most cases, symptomatic treatment by liquid and electrolyte replacement is enough to treat human infections. The use of antibiotics, on the other hand, is controversial. Symptoms typically last for 5-7 days.

Entamoeba histolytica is an important causative agent for diarrhea/dysentery and liver abscess throughout the world. Forms of this parasite may be relatively innocuous, yet the genotype 66, ingested from contaminated food and water, is much more common in those affected by dysentery. Cysts of the protozoa survive outside the host in water, in soils and on foods (especially under moist conditions). The cysts are readily killed by heat and freezing temperatures and survive for only a few months outside of the host. When cysts are swallowed, they cause infections by releasing the trophozoite stage in the digestive tract. The amoeba attaches to colonic mucins (proteins) and epithelial cells after breaking through the mucus barrier. Poor underlying host factors also need be explored regarding the virulence of the infection. Animal immunizations may begin to alleviate the ingestion of Entamoeba, yet they carry a new burden of lowered host immunity due to human ingestion of food-added antibiotics over a lifetime.

Listeria monocytogenes causes gastroenteritis in previously healthy humans and meningitis and focal infections in the immunocompromised and serious infections in pregnant women and babies. It is universal in soil and other material such as sewage, silage, groundwater and vegetation. L. monocytogenes does not form spores and can withstand environmental stressors such as pH change, salinity, low temperatures and metal ions. It may persist in contaminated food-processing environments. Some cases of listeriosis may involve infection via the soil-food processing-oral route.

Shigella (shigellosis), often found in children (and also adults), is a major cause of foodborne infectious colitis generally taken in orally. Most people infected with Shigella develop diarrhea, fever and stomach cramps starting a day or two after they are exposed to the bacteria. The diarrhea often is bloody. Shigellosis usually resolves in 5-7 days. People with shigellosis in the U.S. rarely require hospitalization. A severe infection with high fever may be associated with seizures in children younger than age 2. Some infected people may have no symptoms but can still pass the Shigella bacteria to others.

Special Populations

As with many diseases, special populations are at higher risk for contracting a full-blown infection from minor exposure or secondary exposure to pathogens. The unborn, infants, children, elderly and immunocompromised individuals succumb to foodborne illness faster than adolescents and adults. People with long-standing liver, kidney and cardiac disease also are at higher risk for foodborne illness than those in the general population.

The CDC reports approximately 40 million preschoolers and children per year develop foodborne illness. That number may actually be far higher as many have mild symptoms (mild nausea or vomiting) so parents never seek care. In children, symptoms of severe, often bloody diarrhea, nausea, abdominal cramping (commonly from strains of E. coli and Salmonella) appear within 6 hours after ingestion of contaminated food. In rare cases, children may develop hemolytic uremic syndrome (HUS), a severe complication more often associated with E coli foodborne illness. HUS can be quite severe with complications that may include renal failure, thrombocytopenia and anemia. Symptoms of altered mental state, petechiae (pinpoint purplish, round skin spots), purpura (non-blanching red-purple splotches on skin) and anuria (very little to no urine output) typically occur 5 days following resolution of the diarrhea.

Although Listeria may not cause severe disease in most individuals, older people and those with suppressed immune systems are at risk of potentially fatal illness. Listeria can cause miscarriages in pregnant women due to chorioamnionitis (inflammation of the placental membranes). Even healthy people may experience high fever, lethargy, severe headache, stiffness, nausea, abdominal pain and diarrhea from Listeria food poisoning. Infants present with sepsis and meningitis; older children usually sustain meningitis.

Strains of campylobacter are associated with helicobacter infections of the gastrointestinal tract of males with sexually acquired AIDS. Campylobacter also can be a main cause of traveler's diarrhea. It is often present in seagulls' stool and can infect children in beach areas.

Prevention & Treatment

Because many foodborne illnesses are bacterial in origin, yet self-limited, antibiotics often are unnecessary and treatment can be focused solely on rehydration. With cases of viral foodborne illnesses, no antibiotic treatment is necessary. For the child or adult with suspected foodborne illness, focus is on rehydration, avoiding severe dehydration and monitoring for signs of HUS. Following hours of diarrhea and vomiting, children and elderly may become dehydrated and need fluid and electrolyte replacement through the use of oral electrolyte solutions. If the symptoms do not resolve within 24 hours, hospitalization with intravenous fluid replacement and antibiotics is generally required.

Salmonella infections usually resolve in 5-7 days and often do not require treatment other than oral fluids. People with severe diarrhea may require rehydration with intravenous fluids. Antibiotics, such as ampicillin, trimethoprim-sulfamethoxazole or ciprofloxacin, usually are not necessary unless sepsis ensues. Some Salmonella bacteria have become resistant to antibiotics, largely as a result of the use of antibiotics to promote the growth of food animals.

E-coli (form EHEC) may be prevented by the regular use of probiotics to enhance the integrity of the epithelial barrier in the deep gut.

E. histolytica deep gut infections are treated with nitroimidazole derivatives. They are highly effective against the trophozoite form of the amoeba. Since they have little effect on amoeba cysts, this treatment usually is followed by an agent (such as paromomycin) that acts on the organism in the lumen.

Appropriate antibiotic treatment kills Shigella bacteria and may shorten the illness by a few days. The antibiotics commonly used for treatment are ampicillin, trimethoprim/sulfamethoxazole ceftriaxone or ciprofloxacin for adults. Some Shigella bacteria have become resistant to antibiotics; therefore, when many people in a community are affected by shigellosis, antibiotics are sometimes used to treat only the most severe cases. Antidiarrheal agents such as loperamide or diphenoxylate with atropine can make the illness worse and should be avoided.

Ampicillin is currently the drug of choice for treating Listeria monocytogenes infections. Many antibiotics are effective and are used as second-line agents, although effectiveness varies (e.g., vancomycin, ciprofloxacin, azithromycin).

Limiting Risks

The CDC reports people can cut the risk of getting salmonella and other foodborne illnesses by:

• Cleaning. Wash hands, cutting boards, utensils and countertops after they come into contact with any food.

• Separating. Keep raw meat, poultry and seafood separate from ready-to-eat foods.

• Cooking. Use a food thermometer to ensure that all whole meats are cooked to 145° F (with resting three minutes before carving). Make sure ground meats are cooked to 160° F and poultry is cooked to 165° F.

• Chilling. Keep the refrigerator set below 40°F and refrigerate all foods that can spoil.

• Reporting. Tell the health department about any suspected illness.

• Avoid raw milk, unpasteurized dairy products and unpasteurized juices (like fresh apple cider).

• Avoid swallowing water when swimming or playing in lakes, ponds, streams, swimming pools and backyard "kiddie" pools.

• Have common sense. Don't prepare food for others if you have diarrhea or vomiting. And take special care when preparing food for children, people in poor health, pregnant women and the elderly.

• High-risk groups are urged to avoid soft cheeses, deli meats and salad bar contents.

The CDC's PulseNet (developed in 1996) is a national network of public health and food regulatory agency laboratories that perform standardized molecular subtyping ("fingerprinting") of foodborne disease-causing bacteria to distinguish strains at the DNA level. It is a sophisticated, laboratory-based, molecular (pulsed-field gel electrophoresis) surveillance network often responsible for catching the foodborne illness outbreaks at the outset.

This network's objectives to detect foodborne disease case clusters by pulse-field electrophoresis (PFGE) allow for real-time communication among state, local health departments and international partners; facilitate early identification of common source outbreaks; and help food regulatory agencies identify areas where implementation of new measures are likely to increase the safety of our food supply. Detection is the first step toward prevention and education, so this public health agency is taking a huge step toward protecting our population from foodborne illnesses. Once detected, new methods of treatment can be developed and implemented.

In an attempt to educate about safer food hygiene practices in the home, the Los Angeles County Department of Health established numeric scores for restaurant inspections and publically posted these grades for the establishments. From this grading system, a self-assessment questionnaire (the Food Safety Quiz) was developed for the home consumer to track if the home handling of food was remaining safe. The content of the questions was guided by food safety education principles from the U.S. Department of Agriculture for food preparation: clean, separate, cook and chill. The quiz emphasized such food handling practices as the need to clean and sanitize cutting boards after handling poultry, the safe handling of raw eggs and appropriate methods for the refrigeration of cooked and uncooked foods.

Questionnaires and rating scales like these can be easily disseminated to large portions of the population, translated into various languages to reach our variety of ethnic inhabitants and adapted for use with school children as the youngest educators for food safety.

Need for Prevention

The FDA's FSMA, PulseNet, self-assessment questionnaires for food safety and other tools to detect, prevent, educate, and treat foodborne illness are excellent beginnings to handle and eradicate the devastation to our population. Outbreaks point to the continued need for prevention. Contamination often starts on the farm so more standardized methods for safety need to be in place to test soil, animals prior to slaughter and crops before harvested.

Of course, governmental and private funds are necessary to continue the detection, education, prevention and treatment methods. Public safety demands the attention of regulatory bodies and ongoing evaluation of our consumed products. Consumers are charged with knowledge of safe handling, preparation and storage of the products they eat and drink.

Resources
Baumgardner D. Soil-related bacterial and fungal infections. J Am Board Fam Med. 2012;25(5):734-744.
CDC. Division of Foodborne, Waterborne, and Environmental Diseases. 2012. Available at: http://www.cdc.gov/ncezid/dfwed/index.html. Accessed Jan. 30, 2013.
Daniels N, Mackinnon L, Rowe S, et al. Foodborne disease outbreaks in United States schools. Pediatr Infect Dis J. 2001;21(7):623-628.
Kuo T, Dela Cruz H, Redelings M, et al. Use of a self-assessment questionnaire for food safety education in the home kitchen - Los Angeles County, California, 2006-2008. MMWR Morb Mortal Wkly Rep. 2010;59(34):1098-1101.
Mistry R. Foodborne illnesses in kids: a primer. 2012. Available at: http://www.medscape.com/viewarticle/766871. Accessed Jan. 30, 2013.
Navaneethan U, Giannella R. Infectious colitis. Curr Opin Gastroenterol. 2011;27(1):66-71.
Scallan E, Hoekstra R, Angulo F, et al. (2011). Foodborne illness acquired in the United States. Emerg Infect Dis. 2011;17(1):7-15.
Silk B. (2012). Lysteria: food poisoning's rare but deadly germ. Available at: http://emedicine.medscape.com/article/220684-workup. Accessed Jan. 30, 2013.
Teschke K, Bellack N, Shen H. (2010). Water and sewage systems, socio-demographics, and duration of residence associated with endemic intestinal infectious diseases. BMC Public Health. 2010;10:767.
Vugia D, Cronquist A, Cartter M, et al. (2009). Preliminary FoodNet data on the incidence of infection with pathogens transmitted commonly through food. Morb Mortal Wkly Rep. 2009;58(13): 333-337.
Zach T, et al. (2011). Listeria infection. Medscape. 2011. Available at: http://emedicine.medscape.com/article/965841-overview. Accessed Jan. 30, 2013.

Susan Fralick-Ball is a clinical psychologist and neuropsychologist with an additional 34 years of clinical nursing practice and nursing education in a wide range of specialties. She also is the founder of the PsychMedEd, a medical educational and psychological service practice providing positive psychology, a host of evidence-based psychological therapeutic interventions and medical education for healthcare professionals in Blue Bell, Pa.




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