Purdue University research shows that standard cleaning procedures in retail delis may not eradicate Listeria monocytogenes bacteria.
A study led by Haley Oliver, assistant professor of food science, found that 6.8 percent of samples taken in 15 delis before daily operation had begun tested positive for Listeria monocytogenes In a second sampling phase, 9.5 percent of samples taken in 30 delis during operation over six months tested positive for the bacteria. In 12 delis, the same subtypes of the bacteria cropped up in several of the monthly samplings, which could mean that Listeria monocytogenes can persist in growth niches over time.
Listeria monocytogenes can cause listeriosis – a serious systemic infection – in immunocompromised people such as the elderly, infants and children, pregnant women and people with HIV. In severe cases, L. monocytogenes can pass through the intestinal membrane and into the bloodstream or cross the blood-brain barrier. The bacteria can also cross the placental barrier in pregnant women, which can trigger abortion.
Ready-to-eat deli meats are the food most associated with L. monocytogenes, which can grow at refrigerator temperatures, unlike Salmonella and E. coli.
Stringent control measures and inspections have tamped down the presence of L. monocytogenes at meat processing plants, but there are no regulations specific to Listeria for retail delis. Recent risk assessments suggest that up to 83 percent of listeriosis cases linked to deli meats are attributable to products contaminated at retail.
The paper was published in the Journal of Food Protection.