Staphylococcal Enterotoxin Gene Cluster: Prediction of Enterotoxin (SEG and SEI) Production and of the Source of Food Poisoning on the Basis of v Saβ Typing

Abstract

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.

Staphylococcus aureus in the Processing Environment of Cured Meat Products

“…Different studies have found that S. aureus CC30 is predominant among human nasal carriers of the bacterium [33], and in cases of bacteremia in Denmark [30]. Although it has also been isolated from RTE food [4], it is not one of the major clonal complexes of porcine origin. We cannot rule out a human origin of those isolates.…”

“…Staphylococcal enterotoxins are the main virulence factors associated with S. aureus and the primary cause of staphylococcal food poisoning. Most of the staphylococcal food poisoning outbreaks are classified as weak-evidence outbreaks, as only the classical enterotoxins SEA, SEB, SEC, SED and SEE can be detected commercially [4]. Together with these five SEs, new described enterotoxins and staphylococcal enterotoxin-like proteins Disclaimer/Publisher's Note: The statements, opinions, and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s).…”

Enterotoxin Gene Cluster and selX Are Associated with Atopic Dermatitis Severity—A Cross-Sectional Molecular Study of Staphylococcus aureus Superantigens

“…Therefore, their expression varies among different strains of S. aureus . Nevertheless, the enterotoxin gene cluster (EGC) involves six SAgs (SEG, SElI, SElM, SElN, SElO, SElU) that occur in a set particularly often [ 11 ]. Furthermore, selected novel SEls were identified as core genome elements [ 12 ].…”

Data_Sheet_1.docx

“…However, publicly available reference databases for virulence gene detection in S. aureus isolates (Joensen et al, 2014;Liu et al, 2019;Sayers et al, 2019;Merda et al, 2020) do not enable complete se gene profiling (e.g., ses, set, selw to selz, sel26 and sel27 are missing in the VFDB_Full database, and ses, set, selv to selz, sel26 and sel27 in the VirulenceFinder DataBase) or subtyping of se variants (because they are not or ambiguously annotated in the databases). Studies using these databases as such (Huang et al, 2017;Petit and Read, 2018;Fursova et al, 2020;Karki et al, 2020;Merda et al, 2020;Schwendimann et al, 2021), thus risk underestimating the prevalence of se genes, potentially affecting obtained results. Indeed, more se genes were reported to be present in the isolates with publicly available WGS data after reanalysis with our methods compared with their previously WGS-determined se gene profiles, mainly because of the lack of complete databases in the other studies (Fursova et al, 2020;Merda et al, 2020).…”

“…Thanks to its unparalleled resolution standing out compared with conventional methods (Anderson et al, 2014;Moore et al, 2015;Cunningham et al, 2017;Cremers et al, 2020), it has moreover become the ultimate tool for inferring phylogenetic relationships between bacterial isolates, using core genome MLST (cgMLST) or single nucleotide polymorphism (SNP) analysis. Although WGS was already used to analyze Methicillin-resistant S. aureus strains responsible for nosocomial infections (Anderson et al, 2014;Moore et al, 2015;Peacock and Paterson, 2015;Cunningham et al, 2017;Sabat et al, 2017), it has been scarcely applied for SFP investigation despite the advantages highlighted above (Merda et al, 2020;Schwendimann et al, 2021).…”