Enhanced Sanitation Standard Operating Procedures Have Limited Impact on Listeria monocytogenes Prevalence in Retail Delis

Abstract

In a recent longitudinal surveillance study in 30 U.S. retail delicatessens, 9.7% of environmental surfaces were positive for Listeria monocytogenes, and we found substantial evidence of persistence. In this study, we aimed to reduce the prevalence and persistence of L. monocytogenes in the retail deli environment by developing and implementing practical and feasible intervention strategies (i.e., sanitation standard operating procedures; SSOPs). These SSOPs were standardized across the 30 delis enrolled in this study. SSOP implementation was verified by systems inherent to each retailer. Each deli also was equipped with ATP monitoring systems to verify effective sanitation. We evaluated intervention strategy efficacy by testing 28 food and nonfood contact surfaces for L. monocytogenes for 6 months in all 30 retail delis. The efficacy of the intervention on the delis compared with preintervention prevalence level was not statistically significant; we found that L. monocytogenes could persist despite implementation of enhanced SSOPs. Systematic and accurate use of ATP monitoring systems varied widely among delis. The findings indicate that intervention strategies in the form of enhanced daily SSOPs were not sufficient to eliminate L. monocytogenes from highly prevalent and persistently contaminated delis and that more aggressive strategies (e.g., deep cleaning or capital investment in redesign or equipment) may be necessary to fully mitigate persistent contamination.

Interventions designed to control postpasteurization contamination in high-temperature, short-time-pasteurized fluid milk processing facilities: A case study on the effect of employee training, clean-in-place chemical modification, and preventive maintenance programs

“…Overall, our data indicate that although employees (filler operators, sanitation staff, and maintenance staff) at all 4 facilities received an hour-long GMP training, this did not result in improved milk quality by the assessments performed. Similar negative results were reported by Etter et al (2017), who found that Listeria monocytogenes prevalence was not significantly reduced in 30 retail delicatessens after implementing new sanitation standard operating procedures. In contrast, training has been demonstrated in other cases to result in significant decreases in the populations of sanitary indicator bacteria in environmental and food samples (Cohen et al, 2001;Machado and Cutter, 2017) as well as on the hands of food handlers (Costa Dias et al, 2012).…”

Persistent and sporadic Listeria monocytogenes strains do not differ when growing at 37 °C, in planktonic state, under different food associated stresses or energy sources

“…While more recent work also suggests produce is emerging as another high-risk commodity [4–7], listeriosis remains a concern in deli meats [4, 6, 8–11]. Typically, one may find growth niches, or harborage sites, of Listeria usually in areas that are difficult to clean, such as drains, condenser coils, cold rooms, or microcracks within bulky, heavy processing equipment [12, 13], as well as some food contact surfaces, such as deli slicers, counters, or cutting boards [14]. When water and organic materials are available in niches, L. monocytogenes can not only survive but multiply [15, 16].…”

Lytic Capacity Survey of Commercial Listeria Phage Against Listeria spp. with Varied Genotypic and Phenotypic Characteristics

“…A panel of 426 L. monocytogenes and 49 other Listeria spp. isolates from retail deli environments (Supplementary Table S1) was assembled from previous studies (Simmons et al, 2014;Wang et al, 2015;Etter et al, 2017;Assisi et al, 2020). Among the isolates were 41 L. monocytogenes pulse field gel electrophoresis (PFGE) types, isolates previously defined as persistent (n = 320; isolated at least three times from the same store), transient isolates (n = 91), isolates with increased sanitizer tolerance (n = 47), and isolates with enhanced attachment capacity (n = 99).…”