This multi-institutional study assessed the efficacy of Enterococcus faecium NRRL B-2354 as a non-pathogenic Salmonella surrogate for thermal processing of nonfat dry milk powder, peanut butter, almond meal, wheat flour, ground black pepper, and date paste. Each product was analyzed by two laboratories (five independent laboratories total), with the lead laboratory inoculating (E. faecium or a five-strain Salmonella enterica cocktail of S. Agona, Reading, Tennessee, Mbandaka, Montevideo) and equilibrating the product to the target water activity before shipping. Both laboratories subjected samples to three isothermal treatments (between 65 and 100°C). A log-linear/Bigelow model was fit to survivor data via one-step regression. Based on D80°C values estimated from the combined model, E. faecium was more thermally resistant (P < 0.05) than Salmonella in ), nonfat dry milk powder (DEf-80°C: 100.2 ± 5.8 min; DSal-80°C: 28.9 ± 1.0 min), peanut butter (DEf-80°C: 133.5 ± 3.1 min; DSal-80°C: 57.6 ± 1.5 min), almond meal (DEf-80°C: 34.2 ± 0.4 min; DSal-80°C: 26.1 ± 0.2 min), ground black pepper (DEf-80°C: 3.2 ± 0.8 min; DSal-80°C: 1.5 ± 0.1 min), and date paste (DEf-80°C: 1.5 ± 0.0 min; DSal-80°C: 0.5 ± 0.0 min). Although the combined-laboratory D80°C for E. faecium was lower (P < 0.05) than for Salmonella in wheat flour (DEf-80°C: 9.4 ± 0.1 min; DSal-80°C: 10.1 ± 0.2 min), the difference was ~7%. The zT-values for Salmonella in all products and for E. faecium in milk powder, almond meal, and date paste were not different (P > 0.05) between laboratories. Therefore, this study demonstrated the impact of standardized methodologies on repeatability of microbial inactivation results. Overall, E. faecium NRRL B-2354 was more thermally resistant than Salmonella, which provides support for utilizing E. faecium as a surrogate for validating thermal processing of multiple low-moisture products. However, product composition should always be considered before making that decision.
The findings come from the National Antimicrobial Resistance Monitoring Systems (NARMS) 2019 Integrated Summary, which combines data from the Centers for Disease Control and Prevention (CDC), the Food and Drug Administration (FDA), and the US Department of Agriculture (USDA). The report provides a snapshot of resistance patterns found in bacteria isolated from humans, animals, raw meats from retail outlets (chicken, ground turkey, ground beef, and pork chops), and meat and poultry product samples collected at slaughtering facilities.
In addition to Salmonella, which causes an estimated 1.35 million illnesses and 26,500 hospitalizations each year, the NARMS report also includes resistance data on Campylobacter (1.5 million illnesses and 19,500 hospitalizations), Escherichia coli, and Enterococcus. NARMS monitors these bacteria to detect emerging resistance patterns to the antibiotics that are most important to human medicine, multidrug resistance, and specific resistance genes.
