Food-borne bacteria evolving, becoming more dangerous
Pastor Dale Morgan
Food-borne bacteria evolving, becoming more dangerous*
Updated 10/31/2006 8:03 AM ET
By Elizabeth Weise, USA TODAY
There was deadly E. coli O157:H7 in water samples taken on the Salinas
Valley ranch where the spinach was grown, in wild pigs that rampaged
through the fields, in cattle and calves that grazed nearby, and on cow
manure in adjacent pastures, says Kevin Reilly, deputy director of
prevention services for the California Department of Health Services.
"It's not unusual or unexpected that we'd find O157:H7 in the
environment where those species exist," Reilly says. Three people died
and more than 200 others were sickened in the outbreak that spread to 26
states.
Because E. coli lives in the gut of warm-blooded animals (though it
likes cattle and deer best), it gets transferred between them via what
the squeamish call "fecal contact." People have been experiencing such
contact for as long as there's been farming. Before the advent of modern
agriculture, all fields were fertilized with manure, and wild animals
were abundant.
But today the pathogenic reality of agriculture is different — and
deadly. "The microbial world has changed, but people haven't quite
caught up with it," says Douglas Powell, a professor of pathobiology at
Kansas State University in Manhattan.
It's certainly caught up with us. There have been 20 reported outbreaks
of E. coli O157:H7 in lettuce or leafy greens since 1995. And Monday,
the Centers for Disease Control and Prevention said it is tracking a
salmonella outbreak, possibly linked to produce, which has sickened at
least 172 people in 18 states.
Troubling trends
Several trends have converged to create a perfect storm of dangerous
produce:
•The evolution of ultra-dangerous versions of common food pathogens with
which humans have coexisted for millennia. E. coli lives in the guts of
most mammals. Almost all forms are harmless; some are actually necessary
for health. It wasn't until the 1970s that a deadly version — O157:H7 —
emerged that causes kidney damage and death.
This strain of E. coli was only isolated in 1982 in hamburger, and the
Centers for Disease Control and Prevention has tracked it back as far as
1976. It picked up the ability to produce verotoxin from a closely
related bacteria that causes shigella dysentery, according to the Food
and Drug Administration.
•Two forms of the salmonella bacteria,Salmonella typhimurium and
Salmonella newport, have evolved to resist most of the antibiotics that
doctors are comfortable giving to children, says Patricia Griffin, who
studies food-borne and diarrheal illnesses at the CDC.
Both are most common in cattle and other farm animals but are also
turning up in fresh produce.
•A lack of understanding about what food safety requires. Just last
month five people were paralyzed and had to be put on ventilators
because of botulism from bottled carrot juice. The spores occur
naturally in the soil. In carrot juice, the spores can germinate into
bacteria that grow and produce toxin, says Powell. The juice has to be
refrigerated at temperatures below 40 degrees to inhibit botulism.
Officials suspect that at some point in its journey from the bottling
plant to the consumer's glass, the carrot juice from Bolthouse Farms in
Bakersfield, Calif., was allowed to get too warm, and the spores were
able to multiply and produce their deadly neurotoxin.
"People don't pay enough attention to refrigeration, and that's
absolutely critical with the fresh-cut produce," says Linda Harris, a
professor of microbiology and an expert on food safety at the University
of California-Davis.
•And in a potentially more disturbing development, Harris and other
scientists at UCD have discovered that at least one form of salmonella,
formerly thought to be able to live for only a few days outside of the
gut of a warm-blooded animal, now appears to be able to take up
residence in the soil.
In 2001, Harris and other researchers were brought in to investigate an
outbreak of salmonella in raw almonds in California that couldn't be
traced to any animal. They found it instead in the soil between the rows
of trees.
While researchers had long thought salmonella required body temperature
to live, Harris says it can survive and reproduce at temperatures as low
as 50 degrees. So with moisture from rain, sugar from the almond hulls
and even the coolest of days, the orchard's loam provided a home to the
bacteria in a way no one had thought possible.
These trends are causing scientists to rethink their assumptions about
how bad bugs get into our food. And if conventional wisdom about the
transmission of food-borne illnesses is wrong, getting rid of them is
going to be a whole lot harder, says Jack Guzewich, an epidemiologist at
the FDA's Center for Food Safety and Applied Nutrition.
A call for action
Companies are going to have to start talking not just about how natural
and wholesome their food is, but exactly what they are doing to protect
customers from microbial illnesses, says Powell.
A newly assembled group of produce buyers is calling on three of the
major produce industry associations to come up with new, enforceable
food safety standards.
The buyers represent some of the biggest food retailers, including
Safeway, Costco and Denny's restaurants. They sent a letter to the
Produce Marketing Association, United Fresh Produce Association and
Western Growers Association last Thursday.
They set a Dec. 15 deadline for putting together safety protocols for
lettuce and leafy greens and a Feb. 15 deadline for melons, tomatoes and
green onions.
"We believe the power to change the industry is in the hands of the
buyers," says Tim York, president of Markon Cooperative and leader of
the ad hoc group.