Like lab technicians on a crime-scene television drama, investigators have tracked a strain of bacteria over thousands of miles — from bagged spinach in Midwestern refrigerators to the guts of a wild pig in the hills of California’s central coast.
While they may never pinpoint the exact source of the E. coli blamed for killing three people and sickening more than 200, they have come closer than ever before. And experts say the investigation has yielded valuable clues for preventing future outbreaks.
“We’ve completely overhauled the way we test and package greens,” said Samantha Cabaluna, a spokeswoman for Natural Selection Foods LLC, the company that packaged the tainted spinach. “Regardless of the source or method of contamination, we’re better prepared to catch it.”
But that’s little solace to victims and their families, for whom even a relatively fast and successful investigation like this one has seemed painfully long.
“This was a long, convoluted story that took a long time to unfold,” said Ken Costello, whose elderly mother-in-law was among those who died.
At first, there were only scattered reports of people falling sick. A 6-year-old boy in Wisconsin had bad cramps. A 12-year-old girl in Kentucky was hospitalized with vomiting. Then an elderly woman in Wisconsin died.
With similar food poisoning cases popping up in far-flung states, health officials began posting DNA profiles of the responsible bacteria to a national database operated by the Centers for Disease Control and Prevention.
A pattern emerged: They were all caused by the same strain of E. coli.
It was clear that a widespread outbreak was under way. Epidemiologists zeroed in on a suspect lurking in victims’ refrigerators: bagged spinach.
Suspicion quickly focused on California’s Salinas Valley, a region that grows a large portion of the nation’s fresh spinach and was cited in other recent E. coli outbreaks linked to salad greens.
State officials alerted the U.S. Food and Drug Administration on Sept. 13, and within hours the agency had launched one of the most extensive investigations in its history.
“We put more people and far more resources into this than ever before,” said Jack Guzewich, director of emergency coordination and response for the FDA’s Center for Food Safety and Applied Nutrition.
More than two dozen “food detectives” fanned out across the country. They donned rubber gloves to collect spinach leaves from processing plants. They frightened cows found near fields of greens to induce defecation and collect their manure. They dipped beakers into water used to irrigate farms or wash the spinach.
More than 750 samples were placed in sterile,
temperature-controlled containers, labeled, documented and
delivered to labs for testing. Their aim: to determine where the
contamination occurred along the greens’ journey from field to
The urgency of the investigation rose as the numbers of sick people mounted.
When the California Department of Health Services issued a warning against eating bagged spinach on Sept. 14, the spinach-borne O157:H7 strain of E. coli had been blamed in 49 illnesses across the country, and one death.
The detectives were armed with knowledge gleaned from eight previous investigations of outbreaks linked to California greens. Each had been a frustrating dead end, and the team was intent on achieving a different outcome this time.
Over the summer, FDA investigators were given special training on how to conduct field searches; growers, packers and shippers had been questioned about their practices.
“We knew there was a potential for problems there, and we wanted to be ready in case it happened,” said Guzewich.
Meanwhile, patients were finding bags of leftover spinach in their kitchens. Tests done on the greens told detectives which bags were contaminated.
Codes printed on the bags led detectives to their first breakthrough: they were packaged at a San Juan Bautista plant operated by Natural Selection, one of the nation’s biggest purveyors of bagged salads, which had already issued a pre-emptive voluntary recall.
The detailed coding told investigators the spinach was bagged on Aug. 15 — even indicating the shift and packing line that handled it.
But exhaustive testing of the plant’s equipment and water supply over the next several weeks turned up none of the virulent bacteria, according to health officials and Natural Selection.
Attention then turned to the fields. Using the company’s records, investigators traced the spinach packaged that day to nine farms in three California counties — Santa Clara, San Benito and Monterey.
More contaminated spinach bags were found, with coding that narrowed the search to four fields, Cabaluna said.
By early October, the death toll had risen to three, with many more sickened.
The FDA said the strain of E. coli had been found in manure on a cattle ranch in the Salinas Valley, within a mile of spinach fields. Investigators combed the pastures, gathering more samples, including wildlife and cattle feces, stream water and spinach leaves.
Last week, the effort brought them closer than ever to identifying how bacteria contaminated vegetables implicated in an E. coli outbreak.
Six new samples from the ranch tested positive for the right strain of E. coli, including one found in the guts of a feral pig killed on the property.
There were also signs that pigs had broken through a wire mesh fence to munch on the spinach, pointing to this field as a likely source of the outbreak, and to the wild pigs as probable carriers.
But officials said they’re not ruling out that other fields may also have been a source of bacteria.
Either way, this investigation has already provided the most specific information to date for how a microscopic organism commonly found in animal feces can sicken and kill consumers thousands of miles from the source.
“We’ve never found that in past investigations,” said Kevin Reilly, deputy director of prevention services for the California Department of Health Services.
The investigation continues, but with each day that passes the bacteria’s tracks become harder to follow.
After it’s consumed, E. coli incubates for up to four days. The person who becomes ill might take a week to experience symptoms serious enough to see a doctor. Lab testing and comparing the DNA profile against others in the CDC’s PulseNet database also take time.
In this outbreak, an average of 15 days elapsed between the onset of the first symptoms to the confirmation that the case was connected to the outbreak, according to the CDC.
The quick turnaround time for growing spinach and lettuce can also make it difficult to trace a pathogen to its origin. Fields of baby spinach are planted and harvested within three weeks, the soil is turned over frequently, and packing plants are supposed to be scoured clean every day, agricultural experts said.
“Coastal agriculture in California is extremely dynamic and fluid,” said Steven Koike, a plant pathologist with the University of California, Davis. “There’s a tremendous amount of activity that takes place in a short period of time.”
The relative success of the spinach investigation means little to Ken Costello. His mother-in-law, Ruby Trautz of Bellevue, Neb., became sick after eating spinach salad for three meals in a row.
Trautz died on Aug. 31, before health officials were on the trail of the spinach outbreak, so she was never tested for E. coli. Connecting her case to the outbreak took a fair amount of detective work from Costello, who found the bag of spinach in her refrigerator, sent samples to a private lab, and eventually to state health officials.
Although she was the first person known to have died in the E. coli outbreak, hers was the last of the three fatal cases to be confirmed.
“It was certainly too slow from the standpoint of any kind of prevention,” he said. “And it caused tremendous emotional suffering and needless death.”
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