In many ways, Listeria monocytogenes (Lm)continues to elude industry efforts to eradicate the pathogen from ready-to-eat (RTE) deli meats. Although substantial effort is directed at decreasing Lm-related illnesses by controlling the bacteria within the processing environment, recent studies increasingly suggest that as many as four out of five illnesses are associated with deli meats becoming contaminated while they are being sliced and packaged at retail.

Lm is a serious concern because each year the pathogen causes an estimated 1,600 illnesses, 1,500 hospitalizations and 260 deaths. Moreover, the fatality rate for listeriosis is extremely high. Once infection occurs, Lm will ultimately kill about 16 percent of its victims, compared with only about 0.5 for either Salmonella or E. coli O157:H7.

As a result, FSIS requires processors making RTE deli meats to develop and follow complex Listeria-control programs. Even though these programs have improved the overall safety of deli products dramatically, there are no similar rules requiring deli establishments to control for the pathogen at retail. As a result, many illnesses attributable to the consumption of deli meats are likely resulting from contamination introduced at the deli (not processing) level.

Indeed, in a recent study conducted by Purdue University, researches collected more than 4,500 samples from 30 grocery deli establishments in three states over the course of six months. The study was designed to determine the prevalence of Lm persistence in the retail deli environment. While some Lm contamination will be transient (entering and then quickly leaving the deli environment on contaminated product), the study suggests that a high level of contamination be persistent and remain within the deli environment itself.

Indeed, of all the samples collected, nearly 4.5 percent of the samples collected from food contact surfaces (such as deli slicers) were positive for Lm. About 14.2 percent of all samples collected from non-food contact surfaces (such as floors) were positive for Lm. Thus, on average, nearly 10 percent of all samples collected from the deli environment were positive for the deadly strain.

What is the significance of the study? Well, at the very least, the study should serve as a reminder of the importance of controlling Lm at the processor level. At least some of the contamination that is now known to persist at retail was likely introduced originally from RTE deli meat. Doubling your efforts to control Lm at the processing level will continue to serve an important role in reducing the overall cases of listeriosis annually.

The study is also important, however, because it highlights a significant food safety problem that likely already has a solution. Although 30 percent of the retail establishments sampled had much higher levels of overall contamination than 10 percent, some establishments had none, showing that with some effort Lm can be effectively managed in the retail environment.

Ultimately, everyone who processes or sells deli meats can be adversely affected by the negative publicity associated with such studies. The processing industry has already made significant progress controlling Listeria in the processing environment. Finding ways to share this
expertise with your upstream colleagues, and helping them eradicate Listeria were it is really lurking, will help them make similar progress as well.