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There is a growing demand for safe and convenient meat products. The effect of natural spice extracts incorporated with other hurdles for controlling pathogenic bacteria and extending the shelf life of RTE doner kebab were investigated. A comprehensive literature review was undertaken to establish the status of microbial risk, use of additives, knowledge on oxidative deterioration and HACCP associated with meat products. The in vitro antioxidant and antibacterial activities of spice extracts were screened and compared. Cinnamon, clove, and sumac alcoholic extracts demonstrated strong antimicrobial effect, however, rosemary proved effective as antioxidant in a lamb fat model. An accelerated shelf life study on a model system indicated that storage temperature was the most critical factor affecting lipid oxidation, which was effectively delayed by vacuum packaging and rosemary extracts. The effects of spice extracts, packaging and storage time on physiochemical, microbiological, and sensory attributes of doner kebab were evaluated. Application of rosemary and cinnamon extracts significantly reduced TVC, inhibited LAB, and retarded lipid oxidation rate. Sensory evaluation by a consumer panel indicated that only taste and spiciness perception was significantly different between treatments. A challenge test against Listeria monocytogenes showed significant differences between control and spice treatments at day 28. Strong inhibitory effects were associated to high levels of cinnamon particularly when applied after cooking. The effect of heat treatment and sumac (Rhus coriaria) on Bacillus cereus and Clostridium perfringens inactivation was evaluated on a doner kebab prototype. Addition of sumac significantly reduced D-values and z-values for both organisms in comparison to the control. The investigation of the effect of spice extracts, and environmental conditions on changes in growth kinetic parameters for L. monocytogenes and Salmonella Typhimurium showed that spice extracts are highly significant. For both microorganisms, Mumax was reduced as salt and spice concentrations increased, and pH levels decreased. This study shows that spice extracts incorporated with other hurdles can help to maintain safe and good quality RTE doner kebab.

Listeria monocytogenes is the etiological agent of listeriosis in humans and ruminants causing bacteremia, central nervous system (CNS) infections, abortion, and gastroenteritis among other clinical outcomes. Recent studies have integrated whole genome sequence (WGS), epidemiology data, and host susceptibility to provide evidence for variation in virulence among strains, as a small number of hypervirulent clones have been found linked to a high proportion of human and ruminant invasive listeriosis cases, however, still little is known about variation in virulence across different L. monocytogenes subgroups. To assess and compare the genetic diversity of clinical listeriosis isolates from ruminants in the Upper Great Plains states, we used multilocus sequence typing (MLST) and found that the variation in virulence potential varies among clonal complex (CC), which is reflected in the epidemiology of L. monocytogenes. Based on these results, we evaluated the strains’ virulence potential in Galleria mellonella through larvae survival, LD50, and cytotoxicity, and monitored health index scores and bacterial concentrations post-infection as quantifiable indicators of virulence and immunogenicity. Our findings suggest that strains belonging to CC14, as well as isolates from MN infections are hypervirulent in G. mellonella, as they need a lower bacterial concentration to cause disease and produce a low-level infection that could help in evading the host immune response. We also identify genomic elements associated with strains causing three different clinical outcomes: bacteremia, central nervous system infections, and maternal-neonatal infections. By analyzing 232 whole genome sequences from invasive listeriosis cases, we identified orthologous genes of phage phiX174, transfer RNAs and type I restrictionmodification (RM) system genes along with SNPs in loci associated with environmental adaptation such as rpoB and the phosphotransferase system (PTS) associated with one or more clinical outcomes. Novel genetic variants may be associated with a particular virulence phenotype, as it is likely that strains causing the same clinical outcome share unique genetic elements. Variation in virulence among L. monocytogenes subgroups may confer an increased ability to cross host barriers or higher adaptability to food processing environments, thus the investigation of strainspecific genetic features can impact the design of prevention and management plans for listeriosis.