Listeria monocytogenes contamination of cheese has been a notorious threat to food safety for decades. In 1985, a landmark outbreak of listeriosis linked to Mexican-style cheese caused at least 142 illnesses and 48 deaths/fetal losses in Los Angeles County. Numerous microbiological studies subsequently characterized the growth of L. monocytogenes in various cheese types; a considerable amount of data have been published on specific interactions among Listeria spp. and various cheese properties, including the effects of moisture and other parameters, the roles of aging and ripening, and the importance of production with pasteurized milk. Nevertheless, L. monocytogenes contamination of cheese persists, along with costly recalls and deadly listeriosis outbreaks. Human illness may continue because of the increasing popularity of a diverse array of artisanal cheeses. Recent investigation of a large outbreak in the United States suggests that cross-contaminated cheese maybe an important source of illness. Cross-contamination seems to occur in distribution and retail settings during cutting and repackaging of cheeses, which may be another challenge for control of L. monocytogenes. The symposium begins with an epidemiologist’s historical overview of U.S. outbreaks of listeriosis associated with cheese, and a detailed presentation on the epidemiological, microbiological and product traceback investigations that implicated ricotta salata as a source of illness in the United States. Subsequent presentations by industry representatives and federal officials will share their perspectives on interventions to control L. monocytogenes in cheese. The session’s purpose is to increase stakeholders’ appreciations for the relationships between controlling L. monocytogenes contamination of cheese and overall listeriosis prevention.

Presentations