Truth in numbers?
December 20, 2010
by Alicia Karapetian
Each year some 48 million people become sick due to foodborne illnesses related to foods eaten in the United States, according to a December report from the Centers for Disease Control and Prevention. Among those, 80 percent are from what the report calls “unspecified agents.”
But of the pathogens identified as leading to illness, hospitalization and even death, Salmonella ranked highest on the list of known causes. Approximately 28 percent of deaths and 35 percent of hospitalizations related to a known pathogen were associated with Salmonella from food sources. The other top pathogens, in descending order of concern, were norovirus, Campylobacter, Toxoplasma, E.coli O157, Listeria and Clostridium perfringens.
The new data is the most accurate account of food-related illnesses available and the most comprehensive numbers since 1999.
“People expect food to nourish them, not to harm them,” says Christopher Braden, M.D., director of Atlanta-based CDC's Division of Foodborne, Waterborne and Environmental Diseases. “So we need to intensify efforts to decrease the number of illnesses and deaths due to foodborne diseases.”
Health officials stressed the numbers remain too high. “We must, and can, do better by intensifying our efforts to implement measures that are prevention-oriented and science-based,” said FDA Commissioner Margaret Hamburg, M.D., during the report’s release. “We are moving down this path as quickly as possible under current authorities but eagerly await passage of new food-safety legislation that would provide us with new and long overdue tools to further modernize our food-safety program.”
What the latest figures don’t show, nor do officials acknowledge, is the food source of each illness. Whether those hospitalizations and fatalities are linked to peanut butter, eggs, poultry or some other source, remains unclear.
To that end, poultry processors remain stuck in the middle of a much larger battle. “The industry is doing a very good job of reducing Salmonella contamination on raw chicken,” says National Chicken Council spokesman Richard Lobb. “We’re down to around 5 or 6 percent nationwide, which is a tremendous achievement over the baseline of 20 percent that was set in 1998.”
Nevertheless, the government remains focused on setting new goals and regulations for Salmonella instances and related Salmonellosis infections. The Department of Health and Human Services in early December released its new plan, Healthy People 2020, which outlines its targets for total foodborne diseases instances, and, for the first time, infections related to specific food groups. For poultry, HHS set a goal of 232 Salmonella infections per 100,000 Americans, vs. baseline data from 2005-2007 of 258 reported outbreaks, or a 10 percent drop.
Overall, the goal is to reduce total Salmonella infections to 11.4 occurrences per 100,000 people by 2020 vs. the 2009 actual total of 15.19. The 2010 target was 6.8.
The HHS objective come on the heels of President Obama’s Food Safety Working Group’s new performance standards for Salmonella, which set the maximum allowable percentage of positive tests at 7.5 percent. The standard was last set at 20 percent, updated in 1996.
While the Department of Agriculture projected that some 26,000 Salmonellosis cases would be avoided with adoption of the new standards, poultry products are not the prime offender when it comes to human illness, as evidenced by HHS’s Healthy People 2020 targets. Baseline data show fruits and nuts were responsible for some 311 cases between 2005 and 2007, and dairy products posed the greatest threat, with 786 cases per 100,000 people.
Yet, poultry continues to be a prime regulatory target, and the changing standards are, “always a stretch, always a challenge,” Lobb says. What’s more, he points out, “The [Salmonella positive] numbers count any type of Salmonella, and we know that many of the positive samples are counting Salmonella that typically does not cause human illness, such as Salmonella Kentucky.”
Salmonella testing methods are an increasingly hot market and a prime area of research. For example, Dr. Azlin Mustapha, associate professor of food science at the Univ. of Missouri, Columbia, has developed a test that differentiates between dead and live Salmonella cells. The DNA-based method is fast and accurate. While many rapid tests take from 24 to 48 hours, this approach offers results between two and five hours. Though PCR, or polymerase chain reaction, testing has been widely available for some time, Mustapha approached the process in a different way, looking to distinguish between harmless dead Salmonella cells and live cells that may cause Salmonellosis.
“We incorporated an extra step before PCR in which the cells in the matrix, or chicken, would be stained with a dye that would bind with cells, leaving the DNA from dead cells intact.”
With this approach, she says, the dead cells are bound by the dye and won’t be detected. “If the end result is positive, it would indicate live Salmonella, not dead,” she adds. “The most widely used techniques are culture-based, and you have to grow and wait. They’re not usually reliable. You get a lot of false positives and false negatives.”
To adopt Mustapha’s approach, processors need a PCR real-time testing machine and related commercial kits. “The only difference is that you have to incorporate the extra staining step,” Mustapha says. “It’s very simple. You just stain for five minutes with dye and then expose it to bright light. Keep it on ice and do the PCR test. It’s just an extra few minutes.”
Serotyping Salmonella is an increasing focus as well. Newark, Del.-based SDIX has developed a test for identifying Salmonella enteritidis, the only such method approved by the AOAC Research Institute for SE detection for carcass rinse aides. “So far, the whole concept of serotyping and determining SE is still developing,” says Tim Lawruk, food-safety market manager at SDIX. “But we have a lot of interest from companies and regulatory people.”
Environmental samples are available within two days, allowing processors to determine if SE is in poultry houses. In addition, the test can screen drag swags, pooled eggs and chicken carcass rinses. The company also offers an immunomagnetic separation system to confirm presumptive positive environmental samples.
“We validated the method equivalency to USDA for testing carcass rinses,” Lawruk says. “We took that a step further with the SE test. It’s becoming an issue in the broiler industry as producers try to serotype which Salmonella sub-species are there in the rinse. They’re finding that SE is fairly prevalent, so it’s a good test for them to verify.”
Lawruk notes that the method requires no real capital expenditure, only the presence or use of standard lab equipment and lateral flow test strips. “It’s very easy to use, very accurate compared to the USDA procedure currently used,” he adds.
Proper handling and cooking
Regardless of whether Salmonella ends up on a chicken carcass that makes its way into a home cook’s refrigerator, the fact remains that properly handling and cooking chicken is easiest way to prevent infection.
“The government is considering what else they might do in terms of public education [related to safe handling],” Lobb says. “The instructions are printed on the label with easily understandable pictograms. We’re doing a lot.” Also, NCC continues to work with the Partnership for Food Safety Education.
“I think the consumer does have a responsibility to handle and cook the product properly,” Lobb adds. “But we have also been delivering a product that is safer and safer as the years have gone by.” And the numbers speak for themselves.
Alicia Karapetian is a contributing editor based in the Chicago area.