Battlefront Shifts in Fight Against Beef E coli Outbreaks
The Centers for Disease Control and Prevention (CDC) estimates about 73,480 people are infected each year with E. coli O157:H7, resulting in 600 deaths. Contaminated beef is a leading source of these illnesses and the chronic nature of beef E. coli outbreaks and recalls remains a constant focus of attention among regulators and industry.
Already since December 24, more than 1 million pounds of beef products have been recalled because they had potential to be contaminated with E. coli O157:H7.
Separate stories this week by USA Today reporter Elizabeth Weise and by Scott Canon of the Kansas City Star highlight an important trend in the battle: Intervention at the farm and feedlot level to reduce levels of the bacteria in animals’ guts and hides before they reach slaughter.
“The theory is that animals are carrying higher levels of E. coli during the summer months, and sometimes they may overwhelm the systems in place to control pathogen contamination in (processing) plants,” said James Marsden, a professor of food safety and security at Kansas State University.
As the USA Today story noted, new interventions are intended to flatten out the curve between winter months when less bacteria is entering the system and the April-September period when cattle shed higher concentrations of E. coli O157:H7 and external temperatures are more suitable for the pathogens to cluster.
Each new method, it is hoped, might take down the incidence of E. coli O157:H7 by a factor of 100. Together they could substantially lower the toll inflicted by the disease, which can cause cramps, bloody diarrhea, kidney failure and death. More than 5 percent of infections lead to life-threatening hemolytic uremic syndrome (HUS) or thrombotic thrombocytopenic purpura (TTP).
What follows is a quick run-down on some of the methods being employed to reduce the overall universe of E. coli O157:H7 in cattle:
- Phages: Cattle walk through a car-wash-like spray of bacteria-eating viruses called phages. These viruses are harmless to humans and have been successfully used to kill a spotting bacteria on tomatoes and peppers in agricultures.
- Probiotics: Basically these are bacterial cultures much like those in yogurt, given to cattle in their feed. They’re called “competitive exclusion” cultures because they out-compete the bad bacteria and exclude them in the animals’ guts. The challenge to these is that they are hard to consistenting administer in large feedlot conditions.
- Diet: Research in Texas, Kansas and Idaho has shown that switching cattle from grain to a more expensive diet of high quality hay before slaughter may lower E. coli O157:H7 rates, though the findings have not always been consistent.
- Vaccine: Cargill Meat Solutions is in the midst of an active vaccination program in 100,000 cattle that will reach slaughter this spring. At an estimated cost of $3 to $10 per animal, vaccination against E. coli appears to have the potential to dramatically hinder the population of E. coli in the guts of cattle. A Minnesota-made vaccine called Epitopix already is in trial in the U.S. and Canada has its own E. coli vaccine that could possibly gain approval in the U.S.
From an epidemiologic standpoint, it’s clear that these pre-slaughter interventions lower the E. coli O157:H7 burden in the cattle, says Guy Loneragan, a professor of animal science and expert in O157:H7 in cattle at West Texas A&M University in Canyon, Texas.
Bacteria Control Critical in Stopping Bagged Lettuce E. coli
With the latest issue of Consumer Reports confirming that the produce industry is still selling pre-washed, bagged salad greens that contain problematic levels of bacteria, it’s appropriate to review why this will no doubt lead to another outbreak of E. coli O157:H7, Salmonella or Listeria.
Since 1993, at least 20 Escherichia coli O157:H7 outbreaks have been traced to California-grown leafy greens – primarily lettuce and spinach. Most of these outbreaks involved packaged product that, despite several chlorinated washes, contained sufficient numbers of E. coli O157:H7 to cause infection at the time of consumption.
Although the exact E. coli contamination routes for these products remain unknown, a federal study published in September 2008 indicates that plant tissue damage from processing and also in the field can promote significant multiplication of E. coli O157:H7 over a short time.
The research findings by the Produce Safety and Microbiology Research Unit of USDA’s Agricultural Research Service in California suggest that harvesting and processing are critical control points in the prevention or reduction of E. coli O157:H7 contamination of lettuce.
The research assessed the role of plant tissue damage (mechanical or diseased-induced lesions) in the contamination of leafy greens with E. coli O157:H7 and the growth of the pathogen.
Within only 4 hours after inoculation, the population sizes of E. coli O157:H7 increased 4.0-, 4.5-, and 11-fold on lettuce leaves that were mechanically bruised, cut into large pieces, and shredded into multiple pieces, respectively.
During the same time, E. coli O157:H7 population sizes increased only two-fold on leaves that were left intact after harvest.
Also, the population size of E. coli O157:H7 was 27 times greater on young leaves affected by soft rot due to infection by Erwinia chrysanthemi than on healthy middle-aged leaves. Confocal microscopy revealed that leaf tip burn lesions harbored dense populations of E. coli cells both internally and externally. Investigation of the cut lettuce stems showed that the pathogen grew 11-fold over 4 hours of incubation after its inoculation.
Large Scale Vaccine Trial Started to Prevent Beef E coli Outbreaks
Cargill’s beef packing division is in the midst of a large-scale trial of a vaccine in cattle to combat E. coli O157:H7, a potentially deadly human pathogen that continues to cause massive E. coli ground beef recalls and multi-state outbreaks of E. coli infection.
A Cargill spokesman told the Lincoln Journal Star newspaper in Nebraska that the company is working with feedlot owners to position the slaughter of about 100,000 vaccinated cattle in the May-September period of 2010. The trial involves about a dozen feedlots and Cargill’s beef plant at Fort Morgan, Colorado. Cargill is the largest producer of ground beef in the United States.
While studies have shown varying degrees of effectiveness, many researchers believe E. coli vaccines can reduce the number of animals carrying the bacteria by 65 to 75 percent. While no one contends that vaccines will wipe out the strain of E. coli that causes hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP), a reduction in the volume of bacteria is expected to curtail the number of E. coli O157:H7 outbreaks.
The latest one is an active E. coli restaurant steak outbreak related to the December 24th recall by National Steak and Poultry of 248,000 pounds of boneless steak and other beef products sold to restaurants. Officials so far have said 21 people have been sickened in 16 states, including Michigan, Minnesota, Ohio, Colorado, South Dakota, Washington, Kansas and Iowa.
More common are outbreaks involving ground beef.
According to a review of federal records by national food safety law firm Pritzker Olsen Attorneys, more than 1 million pounds of ground beef and beef cuts intended for grinding were recalled from market in 2009 by USDA-inspected slaughter plants and processors. The largest of the 15 recalls covered 545,699 pounds of ground beef produced this fall by Fairbank Farms of Ashville, N.Y.
Multi-state E. coli outbreaks associated with these recalls killed at least three people and sickened at least 80, according to the records. The outbreaks resulted in at least 34 hospitalizations and eight confirmed cases of life-threatening hemolytic uremic syndrome (HUS), a disease especially dangerous to children that causes kidney failure and many other serious health conditions.
From January 2007 to December 2009, the industry initiated at least 52 recalls of beef tainted with E. coli O157:H7 compared with 20 in the three previous years, according to the New York Times.
Spinach E coli Study Shows Importance of Colder Refrigeration
A very large and deadly spinach E. coli outbreak hit the United States in September 2006 in which 199 people in 26 states were sickened after eating contaminated, bagged spinach grown in San Benito County, California. Four deaths were linked to the outbreak and 102 people were hospitalized, including 31 who developed life-threatening hemolytic uremic syndrome (HUS).
For most Americans, it came as a shock that something as healthy as spinach could cause fatal disease and illness on such a wide scale. Studies have been done since the outbreak on the clustering of pathogenic bacteria inside sealed plastic bags of leafy green produce.
The most recent study, completed in October 2009 by scientists from USDA’s Agricultural Research Service, evaluated the effect of temperature during storage of bagged spinach inoculated with E. coli O157:H7. The results were instructive on how the grocery industry and consumers should pay attention to refrigeration to reduce the threat of microbiological hazards in bagged greens.
The study by Yaguang Luo, Qiang He, James McEvoy and William Conway found that E. coli O157:H7 can grow significantly on commercially packaged spinach held at 46.4 degrees Fahrenheit (8 C) or above before significant product quality deterioration occurs.
Bagged E. coli spinach held at 53.6 degrees (12 C) supported “significant” growth of the bacteria within only three days of storage and continued to grow with each additional day of storage until the spinach became noticeably deteriorated by Day 9.
When held at 46.4 degrees (8 C), E coli initially grew slowly but bacteria growth was significant after 6 days of storage, the study found.
On the contrary, bagged spinach held at 33.8 degrees and 41 degrees experienced significant declines in E. coli O157:H7 populations within 3 days of storage.
E. coli Prevalent in Organic Beef
By Kathy Will
A new study released this summer by researchers at Kansas State University found that organic and naturally raised beef cattle are just as prone to E. coli O157:H7 as conventially raised animals.
Writing in the August 2009 issue of the journal Applied and Environmental Microbiology, the Kansas State scientists said they undertook the study because organic foods are increasingly in demand and foodborne illness outbreaks are a growing concern.
E. coli O157:H7 is the only pathogen defined by U.S. regulators as an illegal adulterant in ground beef. It grows in the digestive tracks of cattle and is expelled in their manure.
Healthy human adults can survive an infection of E. coli O157:H7, but it can cause serious complications and lead to severe illness and death in young children, the elderly and others who have weak immune systems. Children are especially susceptible to hemolytic uremic syndrome, a complication of E. coli O157:H7 infection that attacks a person’s red blood cells and causes myriad damage to the body.
The study, as recapped in Science Digest, collected fecal samples from organically fed and naturally raised cattle. Results showed prevalence rates of 14.8 percent in organically raised cattle and 14.2 percent in naturally raised cattle.
The researchers said those prevalence rates of E. coli O157:H7 are similar to convetionally raised beef cattle. The study also found no major difference in antibiotic susceptibility patterns.
E. coli O157:H7 in Leafy Greens: How Does it Get There?
By Fred Pritzker
It’s relatively easy for the general public to understand the sequence of an E. coli O157:H7 outbreak involving ground beef, but scientists are still studying how the pathogen finds its way from the stomachs of cattle and other hooved animals into fields of vegetables, causing widespread E. coli outbreaks involving lettuce, spinach, tomatoes and other fresh produce.
A study of E. coli O157:H7 contamination in the watershed of the Salinas Valley — otherwise known as America’s salad bowl — offers some interesting insights. It was submitted in October 2007 by nine researchers from the USDA’s Agricultural Research Service, California’s departments of environmental protection and health services and the U.S. Food and Drug Administration with help from the Centers for Disease Control and Prevention.
For background, more E. coli O157:H7 outbreaks are linked to ground beef than they are to vegetables. In the case of beef, the bacteria enter packing plants on the hides of cattle or they are accidentally released during slaughter, landing on the surface of primal cuts. If the cuts are ground into hamburger, the pathogens can survive all the way to a person’s dinner plate if an individual patty isn’t cooked at its center to at least 160 degrees.
Between 1995 and 2006, 22 produce outbreaks E. coli O157:H7 were documented in the United States, with nearly half traced to lettuce or spinach grown in California — mostly in the Salinas Valley. The researchers in the October 2007 study spent 19 months sampling water, soil, plants, feces and sediment throughout the Salinas Valley watershed. They found E. coli O157:H7 at least once in 15 of 22 watershed sites. They found that the incidence of E. coli O157:H7 “increased significantly” when heavy rains caused an increase flow rate in the rivers.
But the study didn’t decipher new risk factors. For instance, researchers weren’t sure if the higher prevalence of E. coli after rains was related to flow rates stirring up E. coli O157:H7 in the sediment of rivers and creeks or if the increased number of positive test results was caused by run-off from grazing areas adjacent to streams and rivers. Even then the researchers were surprised to find that certain strains of E. coli O157:H7 wouldn’t migrate more than 100 yards from a known hot-spot of E. coli. But other matching strains of E. coli O157:H7 were found more than 30 kilometers away from each other.
Overall, the researchers concluded that the incidence of E. coli O157:H7 in the environment in the Salinas Valley is dynamic and not reasonably predictable.. For instance, while the highest incidence of E. coli O157:H7 was detected after rains, the researchers also found evidence of the pathogen making appearances during drought periods. The researchers said it was possible that the micro-organism could travel in the valley in clouds of dust from areas were cattle graze.
The writer, Fred Pritzker, is founder and president of Pritzker Olsen attorneys, a national food safety law firm representing E. coli victims and victims of hemolytic uremic syndrome, or HUS – a severe complication of E. coli O157:H7 infection that can cause permenant health damage or death in young children, the elderly and people who have weakened immune systems. For more information or to reach an E. coli attorney at the firm, call 1-888-377-8900 (Toll Free).
