Effect of Scalding Temperature on Growth of Staphylococcus aureus and Formation of Staphylococcal Enterotoxin during the Production of Alpine Cheese in a Laboratory Cheesemaking Model

Genetic relatedness of Staphylococcus aureus isolates within food outbreaks by single nucleotide polymorphisms

Investigation of bacterial food outbreaks by whole genome sequencing can rely on the inspection of the genetic relatedness between isolates through the application of single nucleotide polymorphism (SNP) thresholds. However, there is no consensus for Staphylococcus aureus in the context of food outbreaks. In this study, we propose a SNP cut-off by taking into account the mutation rate and the evolution time of this pathogen in food. Through in vitro microevolution, we determined the mutation rate of three S. aureus strains grown under mimicked food stressing conditions. From the mutation rate, we set a cut-off of 28 SNPs considering 30 days as evolution time based on the average shelf-life of foods contaminated by S. aureus and the timeline for identifying this pathogen in outbreaks. The SNP threshold was applied to retrospectively study ten staphylococcal food outbreaks to assess whether isolates from food and/or of human origin from the same outbreak were epidemiologically related. To interpret SNP distances, phylogenetic tree topologies and bootstraps were integrated and showed that isolates differing by up to 28 SNPs were monophyletic. Our suggested cut-off can be used in outbreak management to identify closely related S. aureus strains.

Enhancing safety and quality in the global cheese industry: A review of innovative preservation techniques

The global cheese industry faces challenges in adopting new preservation methods due to microbiological decay and health risks associated with chemical preservatives. Ensuring the safety and quality control of hard and semi-hard cheeses is crucial given their prolonged maturation and storage. Researchers are urged to create cheese products emphasizing safety, minimal processing, eco-labels, and clean labels to address consumer health and environmental worries. This review aims to explore effective strategies for ensuring the safety and quality of ripened cheeses, covering traditional techniques like aging, maturation, and salting, along with innovative methods such as modified and vacuum packaging, high-pressure processing, and active and intelligent packaging. Additionally, sustainable cheese preservation approaches, their impact on shelf life extension, and the physiochemical and quality attributes post-preservation are all analyzed. Overall, the cheese industry stands to benefit from this evaluation through enhanced market value, increased consumer satisfaction, and better environmental sustainability.The integration of novel preservation techniques in the cheese industry not only addresses current challenges but also paves the way for a more sustainable and consumer-oriented approach. By continually refining and implementing safety measures, quality control processes, and environmentally friendly practices, cheese producers can meet evolving consumer demands while ensuring the longevity and integrity of their products. Through a concerted effort to embrace innovation and adapt to changing market dynamics, the global cheese industry is poised to thrive in a competitive landscape where safety, quality, and sustainability are paramount.

The Enterotoxin Gene Profiles and Enterotoxin Production of Staphylococcus aureus Strains Isolated from Artisanal Cheeses in Belgium

A Staphyloccoccus aureus is one of the leading causes of food poisoning outbreaks (FPOs) worldwide. Staphylococcal food poisoning (SFP) is induced by the ingestion of food containing sufficient levels of staphylococcal enterotoxins (SEs). Currently, 33 SEs and SE-like toxins (SEls) have been described in the literature, but only five named "classical" enterotoxins are commonly investigated in FPOs due to lack of specific routine analytical techniques. The aims of this study were to (i) establish the genetic profile of strains in a variety of artisanal cheeses (n = 30) in Belgium, (ii) analyze the expression of the SE(l)s by these strains and (iii) compare the output derived from the different analytical tools. Forty-nine isolates of S. aureus were isolated from ten Belgian artisanal cheeses and were analyzed via microbiological, immunological, liquid chromatography mass spectrometry, molecular typing and genetic methods. The results indicated that classical SEs were not the dominant SEs in the Belgian artisanal cheeses that were analyzed in this study, and that all S. aureus isolates harbored at least one gene encoding a new SE(l). Among the new SE(l)s genes found, some of them code for enterotoxins with demonstrated emetic activity and ecg-enterotoxins. It is worth noting that the involvement of some of these new SEs has been demonstrated in SFP outbreaks. Thus, this study highlighted the importance of the development of specific techniques for the proper investigation of SFP outbreaks.

Effects of Gouda cheese and Allium hookeri on thermogenesis in mice

Cheese contains various beneficial nutrients, including calcium and whey protein, as well as large amounts of saturated fatty acids. Thus, intake of cheese increases the production of low-density lipoprotein-cholesterol (LDL-C), a well-defined risk factor for cardiovascular disease. Therefore, identification of natural products that inhibit LDL-C production following cheese intake and verification of the efficacy of such products in animal models are essential. Here, we evaluated the effects of Allium hookeri, a well-known traditional herbal remedy, on metabolism and thermogenesis in mice consuming a cheese-containing diet. Intake of A. hookeri extracts significantly blocked increases in body weight and fat mass caused by intake of Gouda cheese in mice. Additionally, increases in blood triglyceride levels following intake of Gouda cheese were alleviated by A. hookeri. Moreover, intake of Gouda cheese enhanced thermogenesis efficiency. Thus, A. hookeri may have applications as an important additive for reducing the risk of metabolic disease resulting from cheese consumption.