Research conducted at Purdue University has recently revealed that standard cleaning procedures in some retail delis do not eliminate the potentially fatal Listeria monocytogenes bacteria.
Purdue Assistant Professor of Food Science Haley Oliver led the study, finding that 6.8 percent of samples taken in 15 delis before daily store openings tested positive for L. monocytogenes. A second sampling over six months revealed that 9.5 percent of samples taken in 30 delis during business hours tested positive for the bacteria.
"This is a public health challenge," Oliver said. "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."
Eating food contaminated with L. monocytogenes could lead to food poisoning symptoms such as diarrhea or an upset stomach in healthy people, but the bacteria can cause listeriosis in the elderly, infants and children, pregnant women and people with HIV. Listerosis can be fatal in individuals with vulnerable immune systems.
Recent risk assessments suggest that up to 83 percent of listeriosis cases linked to deli meats are can be attributed to products contaminated at the retail level.
"Manufacturing has a zero-tolerance policy for Listeria, but that dissipates at the retail level," oliver said. "The challenge of developing systematic cleaning procedures for a wide variety of delis -- which are less-restricted environments than processing plants -- can make Listeria harder to control. The prevalence of L. monocytogenes is higher than we expected in a significant percentage of delis, and the bacteria is persisting in these delis over time."