Confounding Role of Salmonella Serotype Dublin Testing Results of Boneless and Ground Beef Purchased for the National School Lunch Program, October 2013 to July 2017

Quantitative Risk Assessment of Salmonella in Ground Beef Products and the Resulting Impact of Risk Mitigation Strategies on Public Health

Salmonellosis incidence rates have not declined over the last 15 years in the US despite a significant Salmonella prevalence reduction in meat and poultry products. Ground beef is currently regulated using only qualitative Salmonella criteria, and Salmonella enumeration values have been proposed as an alternative for implementing risk-based mitigation strategies to prevent illnesses. The purpose of this study was to develop a quantitative microbial risk assessment (QMRA) model to estimate the annual number of salmonellosis cases attributable to the consumption of ground beef contaminated with Salmonella and investigate the impact of risk management strategies on public health. Model results estimated 8,980 (6,222-14,215, 90% CI) annual illnesses attributable to ground beef consumption in the US. The removal or diversion of highly contaminated ground beef production lots containing levels above 10 MPN/g (0.4%) and 1 MPN/g (2.4%) would result in a 13.6% (5369-12280, 90% CI) and 36.7% (3939-8990, 90% CI) reduction of annual salmonellosis illnesses, respectively. Frozen ground beef cooked at home was the consumption scenario of highest risk for acquiring salmonellosis. Highly virulent serotypes accounted for 96.7% of annual illnesses despite only being present in 13.7% of ground beef samples. The removal of MDR Salmonella would result in decreased burden of disease with a 44% reduction in acute DALY annually. Focusing salmonellosis reduction efforts on removing highly contaminated ground beef lots, highly virulent Salmonella serotypes, and MDR Salmonella from not-ready-to-eat (NRTE) products were predicted to be effective risk prevention strategies.

Codex Alimentarius Guidelines for Risk Analysis of Foodborne Antimicrobial Resistance Are Incompatible with Available Surveillance Data

ABSTRACT

Foodborne antimicrobial-resistant (AMR) microorganisms are a global food safety concern. Antimicrobial drug use (AMU) in livestock may increase the risk of resistant foodborne bacterial infections in humans via contaminated animal products. Consequently, countries have implemented different livestock AMU restriction policies, opening the potential for trade disputes. AMR risk equivalence between countries with different AMU policies must be established by using scientifically justified risk assessments. The Codex Alimentarius Commission's Guidelines for Risk Analysis of Foodborne Antimicrobial Resistance (AMR Codex) recommends an approach that requires quantification of detailed information, for which, in many instances, little to no data exist. Using AMR Salmonella exposure from beef consumption as an example, we demonstrate the difficulty of implementing the AMR Codex by comparing key regionally specific parameters within the United States and European Union, two regions with substantial beef production and consumption, robust foodborne pathogen sampling and surveillance systems, and different AMU policies. Currently, neither region fully captures data for key regional variables to populate a detailed risk assessment as outlined in the AMR Codex, nor are they able to adequately link AMU in livestock to AMR infections in humans. Therefore, the AMR Codex guidelines are currently aspirational and not a viable option to assess the impact of livestock AMU reductions on the human health risk of AMR salmonellosis from beef or produce regionally comparable estimates of risk. More flexible risk assessment guidelines that more directly link livestock AMU to human health risk and are amenable to currently available data are needed to allow for country variations and to calculate comparable regional risk estimates, which can be used to guide international trade policy.

HIGHLIGHTS

Effects of 405 ± 5-nm LED Illumination on Environmental Stress Tolerance of Salmonella Typhimurium in Sliced Beef

Salmonella Typhimurium is a widely distributed foodborne pathogen and is tolerant of various environmental conditions. It can cause intestinal fever, gastroenteritis and bacteremia. The aim of this research was to explore the effect of illumination with 405 nm light-emitting diodes (LEDs) on the resistance of S. Typhimurium to environmental stress. Beef slices contaminated with S. Typhimurium were illuminated by 405 nm LEDs (18.9 ± 1.4 mW/cm²) for 8 h at 4 °C; controls were incubated in darkness at 7 °C. Then, the illuminated or non-illuminated (control) cells were exposed to thermal stress (50, 55, 60 or 65 °C); oxidative stress (0.01% H₂O₂ [v/v]); acid stress (simulated gastric fluid [SGF] at pH 2 or 3); or bile salts (1%, 2%, or 3% [w/v]). S. Typhimurium treated by 405 nm LED irradiation showed decreased resistance to thermal stress, osmotic pressure, oxidation, SGF and bile salts. The transcription of eight environmental tolerance-related genes were downregulated by the illumination. Our findings suggest the potential of applying 405 nm LED-illumination technology in the control of pathogens in food processing, production and storage, and in decreasing infection and disease related to S. Typhimurium.

Rapid detection of total bacteria in foods using a poly-l-lysine-based lateral-flow assay

Food safety and freshness are evaluated according to microbiological load. To analyze this load rapidly, a poly-_l-lysine-based lateral-flow assay (PLFA) was developed. A total of 90 strains of bacteria that are often detected in spoiled foods, including Enterobacteriaceae, lactic acid bacteria, Pseudomonas, and Bacillus were detected using the PLFA. A positive signal was obtained when the bacterial concentration was ≥6 log₁₀ (cfu/test). A total of 36 fresh foods (meats, pastries, lettuces, cabbages, radishes, and sprouts) and corresponding spoiled foods were cultured for 0, 3, 6, and 9 h to investigate how many hours were required for microbial detection using PLFA. The higher the number of bacteria in a food, the shorter was the culture time required for PLFA-positive results to be obtained, so the distinction between fresh and spoiled food could be made based on the time taken for the culture to become PLFA-positive. The coefficient of determination of the least squares regression between the time to become PLFA-positive and the initial log₁₀ (cfu/g) bacterial count for the food was 0.9888. The test time for the PLFA, including pretreatment, was approximately 15-30 min. This novel method will enable the detection of total bacteria on the food processing site.