Employee- and Management-implemented Interventions Reduce Listeria monocytogenes Prevalence in Retail Delis

Introduction: Deli meats sliced at retail are predicted to cause 83% of deli meat-associated listeriosis cases annually. While L. monocytogenes (LM) is commonly found in delis, environmental prevalence varies by store (0-40%). Enhanced daily SSOPs and a deep clean SSOP executed by a third-party cleaning service immediately reduced LM prevalence in delis, but reductions were often not sustained over time.

Purpose: The purpose of this study was to assess the efficacy of a deep-clean SSOP conducted by store employees and management, complemented with training and facility improvements, all aimed to reduce LM prevalence in stores with known high prevalence and persistence rates.

Methods: Fifty delis among 6 states were screened for LM using a predictive logistic regression model that estimates the probability of high LM prevalence in a deli. The model identified 13 stores with potentially high LM prevalence; 7 stores were confirmed (based on ≥2 of 20 food and non-food contact surfaces positive for LM for ≥2 months) and enrolled for further study. Retail employees, under researcher supervision, executed deep-clean SSOPs; additional interventions (e.g., facilities improvements, training, and education) were incorporated in stores. Environmental samples (n = 20) were collected immediately before and after, and for 6 months post-deep clean.

Results: Deep-cleans immediately reduced LM prevalence in 6 of 7 stores tested.  A total of 22/139 (15.80%) samples before and 8/140 (5.71%) samples after deep-cleaning were positive for LM, a mean decrease of 10.1% positive rate per store (CI₉₅: -0.01, 21.08%; P = 0.066). Interventions reduced average monthly LM prevalence in each store over time by 9.7% (CI₉₅: 2.50, 16.90%; P = 0.017).

Significance:  Employee- and management-executed deep-cleans complemented with training, education, and maintenance programs can reduce LM prevalence, and may play a significant role in preventing cross-contamination of RTE deli meats from the deli environment.