P1-91 Growth of Listeria monocytogenes in Ready-to-Eat Foods: Re-enactment of Observed Domestic Storage Practices Implemented by Older Adults

Monday, July 29, 2013
Exhibit Hall (Charlotte Convention Center)
Ellen Evans, Cardiff Metropolitan University, Cardiff, United Kingdom
Louise Fielding, Cardiff Metropolitan University (UWIC), Cardiff, Wales
Elizabeth Redmond, Cardiff Metropolitan University (UWIC), Cardiff, Wales
Introduction: Internationally, Listeria monocytogenes has the highest rate of reported foodborne disease hospitalizations (< 95%) and related mortality (< 40%). European incidence has doubled almost exclusively among older adults (≥ 60years) since 2001. Majority of incidence is reported to be sporadic; the domestic kitchen is associated with sporadic foodborne disease. Older adults are more susceptible to foodborne disease, and are also reported to frequently consume ready-to-eat (RTE) foods commonly associated with L. monocytogenes. Consequently, implementation of safe food-storage is of paramount importance to reduce the risks of listeriosis in the home.

Purpose: Determine older adults’ food-storage practices of RTE-foods associated with L. monocytogenes in the domestic kitchen and re-enact such practices in a laboratory to assess L. monocytogenes growth.

Methods: Evaluation of older adults (≥ 60 years) (n = 100) food-storage practices in the home (recording of refrigeration temperatures, observation of food-storage practices and microbiological analysis of food contact surfaces) informed the laboratory re-enactment trials. Identified common storage behaviors of older adults were re-enacted with soft-cheese and RTE meat inoculated with ~3.71 log CFU L. monocytogenes, stored at ≤ 5°C (n = 110),  > 5°C (n = 110) and ambient-temperature (n = 55). Food samples were analyzed every 24 hours for up to 21 days.

Results: Key common practices implemented by older adults included prolonged storage of RTE foods and/or refrigeration temperatures > 5°C. Majority (72%) of older-adults’ domestic refrigerators operated at temperatures > 5°C. Most refrigerators (70%) contained foods associated with L. monocytogenes, 54% of which were reportedly stored beyond UK recommendations (2 days after opening) some up to 21 days. Results indicate L. monocytogenes grew at all re-enactment temperatures. Average generation times revealed L. monocytogenes growth was slower at ≤ 5°C (94 h t-1) than at > 5°C (21.5 h t-1) and ambient-temperature (11 h t-1), suggesting older adults’ prolonged storage of RTE-foods at > 5°C/ambient temperature increased L. monocytogeneslevels, making such foods unsafe for consumption.

Significance: Findings indicate that many older adults do not implement practices that concur with food-safety recommendations required to reduce the risk of L. monocytogenes in the home. Re-enactment findings demonstrated L. monocytogenes growth resulting from such practices which may result in RTE-food becoming unsafe for consumption. Findings may be used to inform risk based, targeted consumer food-safety initiatives for older adults to increase implementation of safe food-storage practices to reduce risk of listeriosis in this consumer group.