In the last several weeks have seen an uptick in E. coli cases nationwide. Here are just the ones we know about to date:
Michigan – Health officials say E. coli bacteria have sickened two children and one adult from mid-Michigan. The Mid-Michigan District Health Department said in a statement Wednesday that both children from the Maple Rapids area have been hospitalized. The health department said a third person from the area about 30 miles northwest of Lansing was recovering from an E. coli infection.
Missouri – According to news repots, items purchased at Schnucks salad bars appear to be the source of an E. coli O157:H7 outbreak that has sickened thirty-three region wide, according to a preliminary study conducted by the St. Louis County Health Department. There are reports that the stores involved are located in downtown St. Louis, High Ridge, Ballwin, and Ladue.
North Carolina – The North Carolina Division of Public Health is investigating 26 cases of E. coli in Wake (14), Sampson (6), Durham (1), Franklin (1), Johnston (1), Orange (1) and Wilson (1) counties. Ten of the cases are confirmed, and 16 are still under investigation. Five people – 4 children and 1 adult – are hospitalized. Twenty-three of the 26 outbreak victims attended the State Fair earlier this month.
Wisconsin – Wisconsin’s Green County Health Department and the state Division of Public Health identified four Abe Lincoln Elementary School students infected with the same strain of E. coli O157:H7 responsible for 9 illnesses and one death between mid-August and mid-September. No source has been identified for either the four recent cases or the nine earlier illnesses.
What the Hell is E. coli?
Escherichia coli (E. coli) are members of a large group of bacterial germs that inhabit the intestinal tract of humans and other warm-blooded animals (mammals, birds). Newborns have a sterile alimentary tract, which within two days becomes colonized with E. coli.
More than 700 serotypes of E. coli have been identified. Their “O” and “H” antigens on their bodies and flagella distinguish the different E. coli serotypes, respectively. The E. coli serotypes that are responsible for the numerous reports of contaminated foods and beverages are those that produce Shiga toxin (Stx), so called because the toxin is virtually identical to that produced by another bacteria known as Shigella dysenteria type 1 (that also causes bloody diarrhea and hemolytic uremic syndrome [HUS] in emerging countries like Bangladesh) (Griffin & Tauxe, 1991, p. 60, 73). The best-known and most notorious Stx-producing E. coli is E. coli O157:H7. It is important to remember that most kinds of E. coli bacteria do not cause disease in humans, indeed, some are beneficial, and some cause infections other than gastrointestinal infections, such urinary tract infections. This section deals specifically with Stx-producing E. coli, including specifically E. coli O157:H7.
Shiga toxin is one of the most potent toxins known to man, so much so that the Centers for Disease Control and Prevention (CDC) lists it as a potential bioterrorist agent (CDC, n.d.). It seems likely that DNA from Shiga toxin-producing Shigella bacteria was transferred by a bacteriophage (a virus that infects bacteria) to otherwise harmless E. coli bacteria, thereby providing them with the genetic material to produce Shiga toxin.
Although E. coli O157:H7 is responsible for the majority of human illnesses attributed to E. coli, there are additional Stx-producing E. coli (e.g., E. coli O121:H19) that can also cause hemorrhagic colitis and post-diarrheal hemolytic uremic syndrome (D+HUS). HUS is a syndrome that is defined by the trilogy of hemolytic anemia (destruction of red blood cells), thrombocytopenia (low platelet count), and acute kidney failure.
Stx-producing E. coli organisms have several characteristics that make them so dangerous. They are hardy organisms that can survive several weeks on surfaces such as counter tops, and up to a year in some materials like compost. They have a very low infectious dose meaning that only a relatively small number of bacteria (< 50) are needed “to set-up housekeeping” in a victim’s intestinal tract and cause infection.
The Centers for Disease Control and Prevention (CDC) estimates that every year at least 2000 Americans are hospitalized, and about 60 die as a direct result of E. coli infections and its complications. A recent study estimated the annual cost of E. coli O157:H7 illnesses to be $405 million (in 2003 dollars), which included $370 million for premature deaths, $30 million for medical care, and $5 million for lost productivity (Frenzen, Drake, and Angulo, 2005).
E. coli —a foodborne pathogen
E. coli O157:H7 was first recognized as a foodborne pathogen in 1982 during an investigation into an outbreak of hemorrhagic colitis (bloody diarrhea) associated with consumption of contaminated hamburgers (Riley, et al., 1983). The following year, Shiga toxin (Stx), produced by the then little-known E. coli O157:H7, was identified as the real culprit.
In the ten years following the 1982 outbreak, approximately thirty E. coli O157:H7 outbreaks were recorded in the United States (Griffin & Tauxe, 1991). The actual number that occurred is probably much higher because E. coli O157:H7 infections did not become a reportable disease (required to be reported to public health authorities) until 1987 (Keene et al., 1991 p. 60, 73). As a result, only the most geographically concentrated outbreaks would have garnered enough attention to prompt further investigation (Keene et al., 1991 p. 583). It is important to note that only about 10% of infections occur in outbreaks, the rest are sporadic.
The CDC has estimated that 85% of E. coli O157:H7 infections are foodborne in origin (Mead, et al., 1999). In fact, consumption of any food or beverage that becomes contaminated by animal (especially cattle) manure can result in contracting the disease. Foods that have been sources of contamination include ground beef, venison, sausages, dried (non-cooked) salami, unpasteurized milk and cheese, unpasteurized apple juice and cider (Cody, et al., 1999), orange juice, alfalfa and radish sprouts (Breuer, et al., 2001), lettuce, spinach, and water (Friedman, et al., 1999).
Sources of E. coli Infections
E. coli O157:H7 bacteria and other pathogenic E. coli is believed to mostly live in the intestines of cattle (Elder, et al., 2000) but has also been found in the intestines of chickens, deer, sheep, and pigs. A 2003 study on the prevalence of E. coli O157:H7 in livestock at 29 county and three large state agricultural fairs in the United States found that E. coli O157:H7 could be isolated from 13.8% of beef cattle, 5.9% of dairy cattle, 3.6% of pigs, 5.2% of sheep, and 2.8% of goats. Over seven percent of pest fly pools also tested positive for E. coli O157:H7 (Keen et al., 2003). Stx-producing E. coli does not make the animals that carry it ill. The animals are merely the reservoir for the bacteria.
Foodborne Transmission of Stx-Producing E. coli
E. coli O157:H7 was first recognized as a food borne pathogen in 1982 during an investigation into an outbreak of hemorrhagic colitis (bloody diarrhea) associated with consumption of contaminated hamburgers (Riley, et al., 1983). The following year, Shiga toxin (Stx), produced by the then little-known E. coli O157:H7 was identified as the real culprit.
• In the ten years following the 1982 outbreak, approximately thirty E. coli O157:H7 outbreaks were recorded in the United States (Griffin & Tauxe, 1991). It is important to note that only about 10% of infections occur in outbreaks, the rest are sporadic.
• The actual number is probably much higher because E. coli O157:H7 infections did not become a reportable disease (required to be reported to public health authorities) until 1987 (Keene et al., 1991 p. 60, 73). As a result, only the most geographically concentrated outbreaks would have garnered enough attention to prompt further investigation (Keene et al., 1991 p. 583).
• The CDC has estimated that 83% of E. coli O157:H7 infections are food borne in origin (2009 report)). Consumption of any food or beverage that becomes contaminated by animal (especially cattle) manure/feces can result in disease.
Foods that have been sources of contamination include:
• Ground beef
• Dried (non-cooked) salami
• Unpasteurized milk and cheese
• Unpasteurized apple juice and cider
• Alfalfa, parsley, and radish sprouts
• Lettuce, cabbage, and spinach
• Fruit nuts and berries
• Cookie dough
The Center for Disease Control (CDC), Enteric Disease Branch, released a report dated September 14, 2009 entitled Update on the Epidemiology of Shiga toxin-producing E. coli (STEC) in the United States”. The contents of this timely report have been incorporated into this web piece. CDC’s estimates of the annual number of illnesses caused by Shiga toxin (Stx) producing E. coli (both O157:H7 and non O157:H7) are as follows:
E. coli O157:H7
• 73,000 illnesses
• 2200 hospitalizations
• 61 deaths
• 113,000 illnesses
• 1100 hospitalizations
• 30 deaths
E. coli infections continue to largely be a foodborne illness.
For the period of 1998-2007 during which there were 334 outbreaks, 7864 illnesses), the vehicles for the infections were as follows:
E. coli O157:H7
• Food borne: 69%
• Waterborne: 18%
• Animals or their environment: 8%
• Person-to-person: 6%
• Food borne: 83%
• Waterborne: 9%
• Animals or their environment: 5%
• Person-to-person: 4%
• According to the cited recent CDC report, the mode (kind of food) causing illness secondary to E. coli O157:H7 outbreaks have changed in the past several years. (Note the emergence of leafy vegetables).
E. coli O157:H7
• Beef 33 42
• Leafy vegetable 11 41
• Dairy 13 13
• Fruits-nuts 41 2
• Sprouts 1 2
• Wild Game 0 1
Poultry 2 0
Non-E. coli O157:H7
Fruit (nuts, apple juice and cider, berries) 3
Dairy (cheese, margarine) 2
Leafy vegetables 1
Prevalence of E. coli O157:H7
A 2003 study on the prevalence of E. coli O157:H7 in livestock at 29 US County and three large state agricultural fairs found that E. coli O157:H7 could be isolated from:
13.8% of beef cattle,
5.9% of dairy cattle,
3.6% of pigs,
5.2% of sheep,
2.8% of goats.
7.0% of pest fly pools also tested positive for E. coli O157:H7
The Role of Toxin Receptors
Cattle and other animals are merely reservoirs for the bacteria. Shiga toxin (Stx) producing E. coli do not make the animals carriers ill because their bodies do not have receptors for the toxin. Receptors are tiny protein structures that are located on the surface of cells, and are specific for a particular antigen (substance), in this case, Shiga toxin. They provide a “docking station” for the toxin, without which, it cannot injure animals or their organs (e.g., kidneys).
Animal-to-Person Transmission of E. coli
Animal-to-person spread also occurs, and has been identified in several outbreak-situations as well as in isolated settings, such as homes.
E. coli at Fairs and Petting Zoos
The mode of transmission at agricultural fairs, petting zoos, and farm visits was previously thought to be limited to hand-to-mouth transmission following contact with contaminated surfaces or animals. See www.fair-safety.com
Person-to-Person transmission of E. coli
Outbreaks of E. coli O157:H7 can also be caused by person-to-person transmission, which has occurred in daycare centers, hospitals, nursing homes, and private residences. Because the infectious dose is so small it is very easy for the bacteria to be transmitted among people with close physical contact.
What happens after the Shiga toxin-producing E. coli is ingested?
E. coli infection occurs when a person ingests Shiga toxin (Stx)-producing E. coli (e.g., E. coli O157:H7) after exposure to contaminated food, beverages, water, animals, or other persons. After ingestion, E. coli bacteria rapidly multiply in the large intestine and bind tightly to cells in the intestinal lining. This snug attachment facilitates absorption of the toxin into the small capillaries within the bowel wall where it attaches to globotriaosylceramide (Gb3) receptors.
Inflammation caused by the toxins is believed to be the cause of hemorrhagic colitis, the first symptom of E. coli infection, which is characterized by the sudden onset of abdominal pain and severe cramps, followed within 24 hours by diarrhea (Boyce, Swerdlow, & Griffin, 1995; Tarr, 1995). Hemorrhagic colitis typically occurs within 2 to 5 days of ingestion of E. coli, but the incubation period, or time between the ingestion of E. coli bacteria and the onset of illness, may be as broad as 1 to 10 days.
As the infection progresses, diarrhea becomes watery and then may become grossly bloody, that is, bloody to the naked eye. E. coli symptoms also may include vomiting and fever, although fever is an uncommon symptom.
On rare occasions, E. coli infection can cause bowel necrosis (tissue death) and perforation without progressing to hemolytic uremic syndrome (HUS)—a complication of E. coli infection that is now recognized as the most common cause of acute kidney failure in infants and young children. In about 10 percent of E. coli cases, the Shiga toxin attachment to Gb3 receptors results in HUS.
HUS had been recognized in the medical community since at least the mid-1950’s; however, the syndrome first caught the public’s attention in 1993 following a large E. coli outbreak in Washington State that was linked to the consumption of contaminated hamburgers served at a fast-food chain. A total of 501 E. coli cases were reported; 151 were hospitalized (31%), 45 persons (mostly children) developed HUS (9%), and three died (Bell, et al., 1994).
During HUS, the majority of the toxin gains access to the systemic circulation where it becomes attached to weak receptors on white blood cells (WBC) thus allowing the toxin to “ride piggyback” to the kidneys where it is transferred to numerous strong Gb3 receptors that grasp and hold on to the toxin.
Organ injury is primarily a function of Gb3 receptor location and density. These receptors are probably always in the gut wall and kidneys, but heterogeneously distributed in the other major body organs. This may be the reason that some patients develop injury in other vital organs (e.g., brain, etc.). Once Stx attaches to receptors, it moves into the cells’ cytoplasm where it shuts down the cells’ protein machinery resulting in cellular injury or death, and subsequent damage to vital organs such as the kidney, pancreas, and brain.
How is an E. coli Infection Diagnosed?
Infection with E. coli O157:H7 or other Shiga toxin-producing E. coli is usually confirmed by the detection of the bacteria in a stool specimen from an infected individual. Most hospital labs and physicians know to test for these particular bacteria, especially if the potentially infected individual has bloody diarrhea. Still, it remains a good idea to specifically request that a stool specimen be tested for the presence of shiga toxin-producing E. coli when it is submitted to the lab for testing.
Trace-back and source identification
E. coli O157:H7 is now commonly “fingerprinted.” When a sample is taken from either a piece of meat or poultry that is contaminated with a dangerous form of bacteria, such as E. coli O157:H7, Listeria, Salmonella, or Campylobacter, it can be cultured to obtain and identify the bacterial isolate. If a person consumes some of the contaminated meat or poultry, and becomes infected as a result, a stool sample can then be cultured to obtain and identify the bacterial isolate. These bacterial isolates are then broken down into their various component parts creating a DNA “fingerprint”. The “fingerprint” of the bacteria can then be compared and matched up to the “fingerprint” of isolates from persons who consumed the contaminated product. When DNA “fingerprints” match, they, along with solid epidemiological work, are proof that the contaminated product was the source of the illness.
The process of obtaining the DNA “fingerprint” is called Pulse Field Gel Electrophoresis, or PFGE. This technique is used to separate the DNA of the bacterial isolate into its component parts. It operates by causing alternating electric fields to run the DNA through a flat gel matrix of agarose, a polysaccharide obtained from agar. The pattern of bands of the DNA fragments, or “fingerprints,” in the gel after exposure to the electrical current is unique for each strain and sub-type of bacteria. By performing this procedure, scientists can identify hundreds of strains of E. coli O157:H7 as well as strains of Listeria, Salmonella, and Campylobacter
Treatment for an E. coli Infection
In most infected individuals, symptoms of E. coli infection last about a week and resolve without any long-term problems. Antibiotics do not improve the illness, and some medical researchers believe that these medications can increase the risk of developing HUS (Wong, Jelacic, & Tarr, 2000). Therefore, apart from good supportive care such as close attention to hydration and nutrition, there is no specific therapy to halt E. coli symptoms. The recent finding that E. coli O157:H7 initially greatly speeds up blood coagulation may lead to future medical therapies that could forestall the most serious consequences (Chandler, et al., 2002). Most individuals who do not develop HUS recover within two weeks.
Treatment for those who develop HUS ranges from mild to very intensive. Children are generally in the hospital for about two weeks (range 3 days to 3 months), and adults longer, as their courses tends to be more severe. Since there is no way to end D+HUS, supportive therapy, including meticulous attention to fluid and electrolyte balance, is the cornerstone of survival. For more information about the treatment for HUS, read “What to expect during hospitalization” at www.about-hus.com.
What can we do to protect our families from E. coli?
Since there is no fail-safe food safety program, consumers need to “drive defensively” as they navigate from the market to the table. It is no longer sufficient to take precautions only with ground beef and hamburgers, anything ingested by family members can be a vehicle for infection. Shiga toxin-producing E. coli are now so widely disseminated that a wide variety of foods can be contaminated. Direct animal-to-person and person-to-person transmission is not uncommon. Following are steps you can take to protect your family from E. coli. See also the section what is our government doing to protect us from E. coli?
1. Practice meticulous personal hygiene. This is true not only for family members (and guests), but for anyone interfacing with the food supply chain. Remember that E. coli bacteria are very hardy (e.g., can survive on surfaces for weeks) and that only a few are sufficient to induce serious illness. Since there is no practical way of policing the hygiene of food service workers, it is important to check with local departments of health in order to identify any restaurants that have been given citations or warnings. The emerging practice of providing sanitation “report cards” for public display is a step in the right direction.
2. Be sure to clean and sanitize all imported and domestic fruits or vegetables. All can be carriers of disease. If possible, fruits should be skinned, or at least vigorously scrubbed and/or washed. Vegetables (and of course meat) should be cooked to a core temperature of at least 160 degrees Fahrenheit for at least 15 seconds. If not cooked, fruits and vegetables should be washed to remove any dirt or other material, and then soaked in chlorinated water (1 teaspoon of household bleach in one quart of water, soaked for at least 15 minutes). They can then be rinsed in clean water to remove the chlorine taste. This will remove most, but not all, bacteria. In the case of leafy vegetables, bacteria may not be limited to the leaf’s surface, but can actually reside within the minute circulatory system of the individual vegetable leaves.
3. Be careful to avoid cross contamination when preparing and cooking food, especially if beef is being served. This requires being very mindful of the surfaces (especially cutting boards) and the utensils used during meal preparation that have come in contact with uncooked beef and other meats. This even means that utensils used to transport raw meat to the cooking surfaces should not be the same that are later used to remove the cooked meat (or other foodstuffs) from the cooking surfaces.
4. Do not allow children to share bath water with anyone who has any signs of diarrhea or “stomach flu”. And keep any toddlers still in diapers out of all bodies of water (especially wading and swimming pools).
5. Do not let any family members touch or pet farm animals. Merely cleaning the hands with germ “killing” wipes may not be adequate!
6. Wear disposable gloves when changing the diapers of any child with any type of diarrhea. Remember that E. coli O157:H7 diarrhea initially is non-bloody, but still very infectious. If gloves are not available, then thorough hand washing is a must.
7. Remember that achieving a brown color when cooking hamburgers does not guarantee that E. coli bacteria have been killed. This is especially true for patties that have been frozen. Verifying a core temperature of at least 160 degrees Fahrenheit for at least 15 seconds is trustworthy. Small, disposable meat thermometers are available, a small investment compared to the medical expense (and grief) of one infected family member.
8. Avoid drinking (and even playing in) any non-chlorinated water. There is an added risk if the water (well, irrigation water or creek/river) is close to, or downstream from any livestock.
Irradiation offers the most practical and effective way of sterilizing foods and protecting the consumer. It is already being used for poultry, and is approved for all other foods. Even though the word “irradiation” conjures up fears of radiation exposure, irradiated food does not become “radioactive”; it is safe, and does not change the taste or texture of food. To insure safety the public needs to be educated and the food industry convinced that this will not only protect the consumer, but also will also favorably affect their bottom line. This should be a “no-brainer” given the fact that tainted foods are costing the food industry hundreds of millions of dollars a year (recently, one beef processing company declared bankruptcy following a massive recall of contaminated hamburgers). If this doesn’t work, the food industry may be required to implement this or other equally effective measures.