Food-Borne Pathogen Prevalent in Retail Delis

February 13, 2015
Meghan Ross, Associate Editor

Those with weakened immune systems might want to stay away from their deli's ready-to-go meat.

Those with weakened immune systems might want to stay away from their deli’s ready-to-go meat.

According to new research published in the Journal of Food Protection, retail delis can harbor Listeria monocytogenes, a food-borne pathogen that can cause listeriosis cases and outbreaks. In fact, the US Centers for Disease Control and Prevention (CDC) estimates that the bacterium is behind 2500 listeriosis infections annually.

While the average healthy individual will not develop a serious illness from L. monocytogene, the bacterium can pose a threat to certain populations. For instance, those with weak immune symptoms may experience muscle aches, fever, convulsions, and confusion. Among pregnant women, listeriosis infections can lead to miscarriage, stillbirth, and premature delivery.

Listeriosis can also complicate bone marrow transplantation for cancer patients, according to a study published in Diagnostic Microbiology and Infectious Disease. This 2003 study also found that bacteremia was a common presentation of listeriosis among cancer patients.

Noting that recent risk assessments have suggested retail deli meats might be the source of the majority of human listeriosis cases, Purdue University researchers embarked on a longitudinal study of 30 retail delis across 3 states.

The study’s first phase involved collecting 7 sponge samples on a monthly basis from 15 delis before they opened for business. After 3 months, the researchers wound up with 314 samples, of which 6.8% were positive for Listeria monocytogenes.

In phase 2, the researchers sampled 28 food and nonfood contact sites in 30 delis during daily operation for 6 months. Of the 4503 samples, 9.5% tested positive for L. monocytogenes. The researchers also found 9 of the 30 delis showed a low prevalence of the bacteria on all surfaces.

In addition, the researchers used pulsed-field gel electrophoresis (PFGE) to characterize 446 L. monocytogenes isolates. PFGE provides a DNA fingerprint for the bacterial isolates.

At 12 of the delis, PFGE demonstrated that the same subtypes of the bacteria were found on at least 3 separate occasions, which suggested that the bacteria could persist over time in the delis.

“This is a public health challenge,” said Haley Oliver, PhD, assistant professor of food science at Purdue, in a press release. “These data suggest that failure to thoroughly execute cleaning and sanitation protocols is allowing L. monocytogenes to persist in some stores. We can’t in good conscience tell people with weak immune systems that it is safe to eat at the deli.”

Using information from the CDC, Dr. Oliver told Pharmacy Times that pharmacists could educate their patients in a number of ways. For example, pharmacists could remind patients not to eat meat unless it is heated to an internal temperature of 165°F, or unless it is steaming hot. Pharmacists could also speak with patients about the importance of preventing fluid from hotdogs or lunchmeat from getting onto other food, utensils, or food prep surfaces.