Currently only five (SEA-SEE) out of 27 known staphylococcal enterotoxins can be analyzed using commercially available kits.Six genes (seg, sei, sem, sen, seo, and seu), encoding putative and undetectable enterotoxins, are located on the enterotoxin gene cluster (egc) which is part of the Staphylococcus aureus genomic island vSaβ. These enterotoxins have been described as likely being involved in staphylococcal food poisoning outbreaks.The aim of the present study was to determine if whole genome data can be used for the prediction of staphylococcal egc enterotoxin production, particularly enterotoxin G (SEG) and enterotoxin I (SEI). For this purpose whole genome sequences of 75 Staphylococcus aureus (S. aureus) strains from different origins (food poisoning outbreaks, human, and animal) were investigated applying bioinformatics methods (phylogenetic analysis using the core genome and different alignments). SEG and SEI expression was tested in vitro using a sandwich ELISA method.Strains could be allocated to 14 different vSaβ types, each type being associated with a single clonal complex (CC). In addition the vSaβ type and CC were associated with the origin of the strain (human or cattle derived). The amount of SEG and SEI produced also correlated with the vSaβ type and the CC of a strain. The present results show promising indications that the in vitro production of SEG and SEI can be predicted based on the vSaβ type or CC of a strain.IMPORTANCE Beside the infection properties in human and animals, S. aureus can produce different enterotoxins in food. The enterotoxins can cause vomiting and diarrhea, often involving many people. Most of these outbreaks remain undiscovered as detection methods for enterotoxins are only available for a few enterotoxins, but not for the more recently discovered enterotoxin G (SEG) and I (SEI).In this study we show promising results that in vitro production of SEG and SEI can be predicted based on the whole genome sequencing data of a strain. In addition, this data could be used to find the source (human- or cattle-derived) of an outbreak strain, which is the key for a better understanding of the role SEG and SEI play in foodborne outbreaks caused by S. aureus.

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The aim of this study was to describe the development and evaluation of a steam-mediated heating process for the sanitation of wooden boards used in cheese production. Wooden spruce fir boards from a cheese ripening centre were cut into small blocks and consecutively inoculated with suspensions of Listeria innocua at surface concentrations of 10 4 and 10 2 CFU/cm 2 , respectively. The inoculated blocks were stored at 12°C and 94% relative humidity. Surface cell counts were determined after 24, 72, 144 and 240 h. Samples for the sanitising runs (steam treatment for 20 min with three different temperature programmes between 70 and 78°C) were taken after 168, 192 and 216 h. Although a substantial decrease ([2 log CFU) in cell count occurred, L. innocua survived on the surface of the untreated wooden blocks for the entire timespan of the experiment (240 h), independent of the concentration of L. innocua in the inoculum. All three steam-mediated heating processes presented led to the Listeria-free hygienic status of the treated wood blocks. A comparison of abrasive (shavings) and swabbing (cotton rolls) sampling methods resulted in identical results.

To reduce the number of potential S. aureus contaminated cheese reaching consumers, European legislation stipulates that all cheese must be tested for coagulase-positive staphylococci (CPS) at the point in production when numbers are expected to be highest. If CPS counts exceed 105 CFU/mL, enterotoxin tests must be conducted. In the case the enterotoxin test shows positive results the cheese must be destroyed. Manufacturers of Swiss Alpine cheese are exempt from this legislation because enterotoxin formation in hard cheese is expected to be very unlikely, given the high scalding temperatures the cheese is exposed to during its production. Such temperatures result in inactivation of CPS in the curd. However, this assumption has not yet been scientifically demonstrated. Therefore, a laboratory-scale cheese production experiment was performed, in which the conditions corresponded with certain limitations to practical cheese-making conditions in terms of temperature and time exposure like in Gruyere or Tete de Moine Swiss type cheese. Raw milk aliquots (200 ml) were inoculated with five different strains of CPS, and scalding temperatures, ranging from 46–56° C, were applied during cheese production. The temperatures applied after pressing the curd aimed at reproducing the temperature curve in the peripheral zone of a real cheese wheel. Contrary to expectations, enterotoxin formation occurred and changed with the different scalding temperatures (52–56° C).The differences in enterotoxin formation were more associated with strain type rather than temperature. Based on these results, the mechanism of enterotoxin formation in cheese requires further study.