The gastrointestinal microbiota affects the metabolism of the mammalian host and has consequences for health. However, the complexity of gut microbial communities and host metabolic pathways make functional connections difficult to unravel, especially in terms of causation. In this study, we have characterized the fecal microbiota of hamsters whose cholesterol metabolism was extensively modulated by the dietary addition of plant sterol esters (PSE). PSE intake induced dramatic shifts in the fecal microbiota, reducing several bacterial taxa within the families Coriobacteriaceae and Erysipelotrichaceae. The abundance of these taxa displayed remarkably high correlations with host cholesterol metabolites. Most importantly, the associations between several bacterial taxa with fecal and biliary cholesterol excretion showed an almost perfect fit to a sigmoidal nonlinear model of bacterial inhibition, suggesting that host cholesterol excretion can shape microbiota structure through the antibacterial action of cholesterol. In vitro experiments suggested a modest antibacterial effect of cholesterol, and especially of cholesteryl-linoleate, but not plant sterols when included in model bile micelles. The findings obtained in this study are relevant to our understanding of gut microbiota-host lipid metabolism interactions, as they provide the first evidence for a role of cholesterol excreted with the bile as a relevant host factor that modulates the gut microbiota. The findings further suggest that the connections between Coriobacteriaceae and Erysipelotrichaceae and host lipid metabolism, which have been observed in several studies, could be caused by a metabolic phenotype of the host (cholesterol excretion) affecting the gut microbiota.T he mammalian gastrointestinal tract is colonized by trillions of microorganisms (the gut microbiota), a large fraction of which are bacteria. This microbial community has an extensive impact on host metabolism with important implications for health (1-3). The contribution of the gut microbiota to energy harvest from the diet and to fat storage constitutes a key beneficial trait that underlies host-microbiota symbiosis in mammals (4). However, this contribution has likely become detrimental to modern humans living in societies with excess food resources, as it increases susceptibility to metabolic disorders, such as obesity, type 2 diabetes, and coronary heart disease. Accordingly, the gut microbiota is increasingly being accepted as an important factor that contributes to pathological conditions associated with obesity (5), and in humans, metabolic pathologies often are associated with alterations in the gut microbiota (which is referred to as dysbiosis) (6-9). Unfortunately, there is still little consensus on the bacterial groups that are linked to obesity-related diseases and metabolic phenotypes (3). In addition, although comparisons between germ-free and conventional mice and rats have clearly established a role of the microbiota in modulating host lipid metabolism (2, 10-12), it remai...

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Based on recent risk assessments, up to 83% of listeriosis cases from deli meat in the United States are predicted to be from ready-to-eat deli meats contaminated during processing at retail grocery stores. Listeria monocytogenes is known to use sanitizer tolerance and biofilm formation to survive, but interplay of these mechanisms along with virulence potential and persistence mechanisms specific to deli environments had yet to be elucidated. In this study, 442 isolates from food and nonfood contact surfaces in 30 retail delis over 9 months were tested for inlA premature stop codons (PMSCs); inlA encodes InlA, which is necessary to cause listeriosis. A total of 96 isolates, composed of 23 persistent and 73 transient strains, were tested for adhesion and biofilm-forming ability and sanitizer tolerance. Only 10/442 isolates had inlA PMSCs (p<0.001). Strains with PMSCs were not persistent, even in delis with other persistent strains. Most (7/10) PMSC-containing isolates were collected from food contact surfaces (p<0.001); 6/10 PMSC-containing isolates were found in moderate prevalence delis (p<0.05). Persistent strains had enhanced adhesion on day 1 of a 5-day adhesion-biofilm formation assay. However, there was no significant difference in sanitizer tolerance between persistent and transient strains. Results suggest that foods contaminated with persistent L. monocytogenes strains from the retail environment are (1) likely to have wild-type virulence potential and (2) may persist due to increased adhesion and biofilm formation capacity rather than sanitizer tolerance, thus posing a significant public health risk.

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.

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Listeria monocytogenes is a foodborne pathogen that causes an estimated 1,591 cases of illness and 255 deaths annually in the United States, the majority of which are attributed to ready-to-eat deli meats processed in retail delis. Because retail delis distribute product directly to consumers, rapid methods to validate cleaning and sanitation are needed to improve retail food safety. This study investigated the relationships among ATP levels, standard aerobic plate count (APC), and L. monocytogenes presence in fully operational delis. Fifteen full-service delis were concurrently sampled for ATP, APC, and L. monocytogenes during preoperational hours once monthly for 3 months. Fifteen additional delis were recruited for 6 months of operational sampling (n = 30). A 1-log increase in APC was equivalent to a 3.3-fold increase in the odds of detecting L. monocytogenes (P < 0.001) and a 1.9-log increase in L monocytogenes population (P = 0.03). An ATP level increase of 1 log relative light unit correlated to a 0.22-log increase in APC (P < 0.001). A preoperational ATP level mean increase by 1 log relative light unit increased the odds of detecting L. monocytogenes concurrently fourfold. A 0.5-log increase in mean ATP level during preoperational sampling corresponded to a 2% increase in the predicted L. monocytogenes prevalence during operation (P < 0.01). Additionally, 10 statistically representative sites were identified and recommended for use in sanitation monitoring programs. Our data support the use of ATP as a rapid method to validate effective cleaning and sanitation to reduce L. monocytogenes in retail delis.

The objective of this study was to develop and assess the efficacy of an aggressive deep cleaning sanitation standard operating procedure (DC-SSOP) in nine retail delicatessens to reduce persistent Listeria monocytogenes environmental contamination. The DC-SSOP was developed from combined daily SSOPs recommended by the Food Marketing Institute and input from experts in Listeria control from food manufacturing and sanitation. The DC-SSOP was executed by a trained professional cleaning service during a single 12-h shutdown period. A modified protocol from the U.S. Food and Drug Administration Bacteriological Analytical Manual was used to detect L. monocytogenes in samples from 28 food and nonfood contact surfaces that were collected immediately before and after each cleaning and in samples collected monthly for 3 months. The DC-SSOP significantly reduced L. monocytogenes prevalence overall during the 3-month follow-up period and produced variable results for persistent L. monocytogenes isolates. Six delis with historically low to moderate L. monocytogenes prevalence had no significant changes in the number of samples positive for L. monocytogenes after deep cleaning. Deep cleaning in very high prevalence delis (20 to 30% prevalence) reduced L. monocytogenes by 25.6% (P < 0.0001, n = 294) overall during the follow-up period. Among delis with extremely high prevalence (>30%), positive samples from nonfood contact surfaces were reduced by 19.6% (P = 0.0002, n = 294) during the follow-up period. The inability of deep cleaning to completely eliminate persistent L. monocytogenes was likely due to the diverse infrastructures in each deli, which may require more individualized intervention strategies.

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