Staphylococcal Enterotoxin Type Research Articles

Staphylococcal food poisoning outbreaks occurred in Sicily (Italy) from 2009 to 2016

Notification of foodborne outbreaks has been mandatory in Europe since 2005, and surveillance is carried out along the entire food chain. Here we report the results obtained from laboratory investigations about four cases of foodborne outbreaks that occurred in Sicily between 2009 and 2016, deemed to be related to staphylococcal enterotoxins (SEs) and coagulase-positive Staphylococci (CPS) by the Local Public Health Authority. Primosale cheese samples were processed by culture methods for enumeration of CPS and immunoenzymatic assays for detection and differentiation of the SEs possibly contained in food samples. In all cases, the mistrusted foods were found to be contaminated by CPS at bacterial loads between 5 and 8 log CFU/g and contained SE type C (SEC). The reported data confirm the risk of staphylococcal food poisoning associated with the consumption of raw milk cheese. The SEC is the most commonly occurring SE in goat milk and dairy products and the most represented enterotoxin in Sicilian dairy products. Our results highlighted the need for improving the current monitoring efficiency and implementing the available laboratory methods to collect more faithful epidemiological data on the current prevalence of staphylococcal toxins in the food chain, including SEs currently not detectable by validated analytical methods.

Coordination of prophage and global regulator leads to high enterotoxin production in staphylococcal food poisoning-associated lineage.

The importance of this study lies in its unveiling of a molecular regulatory mechanism associated with the most important food poisoning toxin and the evolution of Staphylococcal food poisoning (SFP)-associated clone. SFP is primarily caused by Staphylococcus aureus, with Staphylococcal enterotoxin A (SEA) being commonly involved in many cases. Thus, SEA has been recognized as a major toxin type. However, despite almost a century since its discovery, the complete mechanism of SEA production is as yet unknown. In this study, we analyzed an SEA-producing SFP clone isolated in East Asia and discovered that this strain, besides acquiring the high SEA-producing phage, exhibits remarkably high SEA production due to the low activity of SarS, an intrinsic regulatory factor. This is the first report documenting the evolution of the SFP clone through the coordinated action of exogenous mobile genetic factors and endogenous regulators on this notorious toxin.

Staphylococcus aureus induces drug resistance in cancer T cells in Sézary syndrome

AbstractPatients with Sézary syndrome (SS), a leukemic variant of cutaneous T-cell lymphoma (CTCL), are prone to Staphylococcus aureus infections and have a poor prognosis due to treatment resistance. Here, we report that S aureus and staphylococcal enterotoxins (SE) induce drug resistance in malignant T cells against therapeutics commonly used in CTCL. Supernatant from patient-derived, SE-producing S aureus and recombinant SE significantly inhibit cell death induced by histone deacetylase (HDAC) inhibitor romidepsin in primary malignant T cells from patients with SS. Bacterial killing by engineered, bacteriophage-derived, S aureus–specific endolysin (XZ.700) abrogates the effect of S aureus supernatant. Similarly, mutations in major histocompatibility complex (MHC) class II binding sites of SE type A (SEA) and anti-SEA antibody block induction of resistance. Importantly, SE also triggers resistance to other HDAC inhibitors (vorinostat and resminostat) and chemotherapeutic drugs (doxorubicin and etoposide). Multimodal single-cell sequencing indicates T-cell receptor (TCR), NF-κB, and JAK/STAT signaling pathways (previously associated with drug resistance) as putative mediators of SE-induced drug resistance. In support, inhibition of TCR-signaling and Protein kinase C (upstream of NF-κB) counteracts SE-induced rescue from drug-induced cell death. Inversely, SE cannot rescue from cell death induced by the proteasome/NF-κB inhibitor bortezomib. Inhibition of JAK/STAT only blocks rescue in patients whose malignant T-cell survival is dependent on SE-induced cytokines, suggesting 2 distinct ways SE can induce drug resistance. In conclusion, we show that S aureus enterotoxins induce drug resistance in primary malignant T cells. These findings suggest that S aureus enterotoxins cause clinical treatment resistance in patients with SS, and antibacterial measures may improve the outcome of cancer-directed therapy in patients harboring S aureus.

Molecular Characteristics and Pathogenicity of Staphylococcus aureus Exotoxins.

Staphylococcus aureus stands as one of the most pervasive pathogens given its morbidity and mortality worldwide due to its roles as an infectious agent that causes a wide variety of diseases ranging from moderately severe skin infections to fatal pneumonia and sepsis. S. aureus produces a variety of exotoxins that serve as important virulence factors in S. aureus-related infectious diseases and food poisoning in both humans and animals. For example, staphylococcal enterotoxins (SEs) produced by S. aureus induce staphylococcal foodborne poisoning; toxic shock syndrome toxin-1 (TSST-1), as a typical superantigen, induces toxic shock syndrome; hemolysins induce cell damage in erythrocytes and leukocytes; and exfoliative toxin induces staphylococcal skin scalded syndrome. Recently, Panton-Valentine leucocidin, a cytotoxin produced by community-associated methicillin-resistant S. aureus (CA-MRSA), has been reported, and new types of SEs and staphylococcal enterotoxin-like toxins (SEls) were discovered and reported successively. This review addresses the progress of and novel insights into the molecular structure, biological activities, and pathogenicity of both the classic and the newly identified exotoxins produced by S. aureus.

Designing a novel chimeric multi-epitope vaccine subunit against Staphylococcus argenteus through artificial intelligence approach integrating pan-genome analysis, in vitro identification, and immunogenicity profiling

Staphylococcus argenteus is a newly identified pathogen that causes respiratory tract infections, skin infections, such as cellulitis, abscesses, and impetigo, and currently, there is no licensed vaccine available against it. To develop a vaccine against S. argenteus, a bacterial pan-genome analysis was applied to identify potential vaccine candidates. A total of 4908 core proteins were retrieved and utilized for identifying four proteins, including SG38 Panton-Valentine leukocidin LukS-PV protein, SG62 staphylococcal enterotoxin type A protein, SG39 enterotoxin B protein, and SG43 enterotoxin type C3 protein as potential vaccine candidates. Epitopes were predicted for these proteins using different types of B and T-cell epitope prediction tools, and only those with a non-toxic profile, antigenic, non-allergenic, and immunogenic were selected. The selected epitopes were linked to each other to form a multi-epitope vaccine construct, which was further linked to the PADRE sequence (AKFVAAWTLKAAA) and 50s ribosomal L7/L12 protein to enhance the vaccine’s antigenicity. The three-dimensional structure of the vaccine construct was assessed to determine its binding affinity with key Toll-like receptor 9 (TLR-9) and Toll-like receptor 5 (TLR-5) immune cell receptors. Our findings demonstrate that the vaccine exhibits favorable binding interactions with these immune cell receptors, indicating its potential efficacy. Molecular dynamic simulations further confirmed the accessibility of vaccine epitopes to the host immune system, substantiating its ability to elicit protective immune responses. Taken together, this study highlights the promising candidacy of the modeled vaccine construct for future in vivo and in vitro experimental investigations. Communicated by Ramaswamy H. Sarma

Molecular Detection of Enterotoxigenic Staphylococcus aureus in Ready-to-eat Cowhide (‘Ponmo’) Collected from Lagos Metropolis, Nigeria

Aims: Ready-to-eat [RTE] animal products like ponmo are preferred by consumers due to its palatability and quality. However, foodborne pathogens particularly Staphylococcus aureus are sources of concern due to cross-contamination of raw and cooked cowhide. This study aimed to investigate the incidence of enterotoxigenic S. aureus in ready-to-eat locally processed cowhide.
 Methodology: Sixty (60) RTE cowhide samples were collected from different locations in Lagos, Nigeria and analyzed using conventional microbiological and molecular techniques for the detection of toxigenic S. aureus contamination. Suspected S. aureus isolates were confirmed by the presence of thermostable endonuclease [nuc] gene in their genome.
 Results: Result showed that 25 (41.67%) and 20 (33.50%) samples harbored coagulase-positive S. aureus and 20 other bacterial species different from S. aureus, respectively while 15 (24.83%) of the tested ponmo samples yielded no bacterial growth. Thirteen of the 15 randomly selected from the 25 suspected isolates were confirmed as S. aureus by the presence of thermostable endonuclease [nuc] gene in their genome. Enterotoxigenic genes were confirmed in all the 13 PCR detected S. aureus. Enterotoxin B gene is most prevalent in ponmo. Multiplex PCR detection of S. aureus enterotoxins [SE] genes revealed the molecular detection of different isolates carrying staphylococcal enterotoxin types A and B, mixed strain carrying both staphylococcal enterotoxins type A and type D. Antibiotic susceptibility of 20 S. aureus isolates revealed varying degrees of susceptibility patterns against the antimicrobial agents. Generally, gentamicin 70% (14/20), azithromycin 75% (15/20), co-trimoxazole 85% (17/20), levofloxacin 95% (19/20) were the most effective antibiotics to S. aureus. A low, ≥50% susceptibility was recorded to chloramphenicol 55% (11/20) and nitrofurantoin 65% (13/20). A higher resistance to streptomycin (90%; 18/20) and ceftazidime (95%; 19/20) was identified, with resistance to ceftazidime being the highest (95%; 19/20).
 Conclusion: It can be concluded that RTE ponmo vended in the study sites is of low hygienic quality and may be of health risk to consumers. High level hygiene practice and good manufacturing practices are required during the production, distribution and marketing of ponmo to curb the potential health consequences of eating ponmo.

Prevalence of staphylococcal toxin in food contaminated by Staphylococcus spp.: Protocol for a systematic review with meta-analysis.

Food contamination by Staphylococcus spp. enterotoxigenic strains is quite common and despite underreporting caused by the short duration of clinical symptoms and lack of medical care, staphylococcal food poisoning is one of the most common Foodborne Diseases (FBD) in the world. This study describes a systematic review protocol with meta-analysis on the prevalence and types of staphylococcal enterotoxins in food, and the profile of contaminated foods. The research will be conducted through the selection of studies reporting the analysis of staphylococcal enterotoxins in food contaminated by Staphylococcus spp. Searches will happen on the following databases: Medline (OVID), GALE, Science Direct, CAB Direct (CABI), Google Scholar, in addition to manual search in the list of references of articles, directory of theses and dissertations, and countries' health agencies. Reports will be imported into the application Rayyan. Two researchers will independently select studies and extract data, and a third reviewer will solve conflicting decisions. The primary outcome will be the identification of staphylococcal enterotoxins in food, and the secondary outcomes will include staphylococcal enterotoxin types and foods involved. To assess the risk of bias in the studies, the tool developed by the Joanna Briggs Institute (JBI) will be used. For data synthesis, a meta-analysis will be performed. However, in case that is not possible, a narrative synthesis of the most relevant results will be carried out. This protocol will serve as the basis for a systematic review that aims to relate the results of existing studies on the staphylococcal enterotoxin prevalence and types in food, and the profile of the contaminated foods. The results will broaden the perception of food safety risks, highlight existing literature gaps, contribute to the study of the epidemiological profile and may guide the allocation of health resources for the development of preventive measures related. PROSPERO registration number: CRD42021258223.

Virtual screening of truncated single stranded DNA aptamers for Staphylococcal enterotoxin type A

Single stranded DNA (ssDNA)/RNA aptamers, are screened through the labor intensive, iterative Systematic Evolution of Ligand by Exponential Enrichment process (SELEX) method. Complete sequence of screened aptamers never interacts with target or participates in final structure. Hence, in silico tools can be used to redesign a short length aptamer from previously reported aptamers which can have high affinity and specificity to the target. This approach is fast, cost effective, and less laborious than in vitro SELEX towards finding an aptamer sequence with better affinity with the target. Here, Staphylococcal enterotoxin type A (SEA) was used as target. A total of nine aptamers reported for different Staphylococcal food poisoning (SFP) enterotoxins were used as a starting pool. The aptamers were variously truncations and thoroughly analyzed through in silico methods. Three truncated aptamers namely AptSEA1.4, AptSEA2.4 and AptSEA8.4 were found to show higher affinity with target SEA. The computational data was also validated with DOT BLOT assay complemented with image analysis. These results also confirmed that the % specific binding and the dissociation constant (Kd) of truncated aptamers AptSEA1.4, AptSEA2.4 and AptSEA8.4 was better than their original counterparts. The truncated aptamers showed great promise to be used as a capture reagent in developing a sensitive assay for detection of SEA. Communicated by Ramaswamy H. Sarma

Multiplex Detection of 24 Staphylococcal Enterotoxins in Culture Supernatant Using Liquid Chromatography Coupled to High-Resolution Mass Spectrometry

Staphylococcal food poisoning outbreaks are caused by the ingestion of food contaminated with staphylococcal enterotoxins (SEs). Among the 27 SEs described in the literature to date, only a few can be detected using immuno-enzymatic-based methods that are strongly dependent on the availability of antibodies. Liquid chromatography, coupled to high-resolution mass spectrometry (LC-HRMS), has, therefore, been put forward as a relevant complementary method, but only for the detection of a limited number of enterotoxins. In this work, LC-HRMS was developed for the detection and quantification of 24 SEs. A database of 93 specific signature peptides and LC-HRMS parameters was optimized using sequences from 24 SEs, including their 162 variants. A label-free quantification protocol was established to overcome the absence of calibration standards. The LC-HRMS method showed high performance in terms of specificity, sensitivity, and accuracy when applied to 49 enterotoxin-producing strains. SE concentrations measured depended on both SE type and the coagulase-positive staphylococci (CPS) strain. This study indicates that LC-MS is a relevant alternative and complementary tool to ELISA methods. The advantages of LC-MS clearly lie in both the multiplex analysis of a large number of SEs, and the automated analysis of a high number of samples.

Inhibition of the sea Gene Expression in Staphylococcus aureus Using the Aqueous and Alcoholic Extracts of the Grapevine (Vitis vinifera L.) Seeds.

Staphylococcus aureus is an important etiological agent for causing food poisoning leading to high mortality in the world. The sea gene is encoded in a polymorphic family of temperate bacteriophage chromosomes and became a prophage, and the transcription of this gene is associated with the life cycle of this prophage. It has been suggested that the grape polyphenols can eradicate the enterotoxin production of food-borne bacteria. This study aimed to evaluate the activity of the aqueous and alcoholic extracts of the grape seeds in inhibiting the expression of the sea gene encoding staphylococcal enterotoxin type A in S. aureus isolated from different sources. This study used five enterotoxin A producing isolates belonging to S. aureus. The results showed that minimum inhibition concentration and sub-minimum inhibition concentration of the aqueous extract were 32 and 16 µg/mL for all isolates, respectively. However, in the case of the alcoholic extract, these concentrations were 16 and 8 µg/mL for all isolates, respectively, and the results of the chemical analysis of the aqueous and alcoholic extracts confirmed that they contain active chemical compounds, such as flavonoids, alkaloids, tannins, and glycosides; moreover, they contain many functional groups according to the analysis of the infrared spectrum. Both extracts were shown to be active in inhibiting the expression of the sea gene in the isolates under study. As the results indicated, the gene expression of these isolates was inhibited by approximately 0.31-0.63 fold, and all pathogenic and environmental isolates showed a decrease in the expression of this gene. These results practically open the door to the possibility of using these extracts to inhibit the ability of S. aureus to produce these dangerous enterotoxins; thereby decreasing or preventing their pathogenicity, especially their food poisoning infections.

Analyses of the complex formation of staphylococcal enterotoxin A and the human gp130 cytokine receptor.

Superantigens (SAgs) are bacterial enterotoxins produced by Staphylococcus aureus. Staphylococcal enterotoxin type A (SEA), a staphylococcal superantigen, has been shown to bind to the cytokine signalling receptor glycoprotein 130 (gp130). The structural details, as well as the exact physiological role of this interaction, remain unclear. Here, we describe the structural details of the SEA-gp130 complex by combining crosslinking mass spectrometry and computational modelling. Interestingly, SEA is not able to bind gp130-homologues from rat and mouse. Our data suggest that SEA may interact with human gp130 in a different manner than other known gp130-ligands. Moreover, the fact that SEA does not bind mouse or rat gp130 suggests that SAgs have additional mechanisms of action in humans.

Effects of Staphylococcus aureus enterotoxin type A on inducing the apoptosis in cervical cancer cell line

Recently, a number of studies have revealed that biotoxins present great potential as antitumor agents, such as some bacteria toxins, so they could be used as chemotherapeutic agents against tumors. In this study, the effects of Staphylococcus aureus enterotoxin type A on BAK, FAS, BAX, TNF-α, p53, BCL-2 and Survivin genes expression in HeLa cell lines were investigated. These cells are transfected with the pcDNA3.1(+)-sea (recombinant) and pcDNA3.1(+) (non-recombinant) plasmids. The expression of BAK, FAS, BAX, TNF-α, p53, BCL-2 and Survivin genes in transfected cells were then analyzed by real time PCR. The results showed an increase in the expression of BAK, FAS, BAX, TNF-α and p53 genes and decreased BCL-2 and Survivin expression at a significant level. As compared to the HeLa cell, which did not receive the sea gene, the cells containing the toxin gene had progressed more towards apoptosis. Staphylococcal enterotoxin type A has an inhibitory effect on the growth, proliferation and invasion of breast and cervical cancerous cells through altering the expression of the genes involved in the apoptosis process. Therefore, it seems that there is a good research field for the use of this toxin in the control and treatment of such malignancies.

Molecular Characteristics of Staphylococcus aureus From Food Samples and Food Poisoning Outbreaks in Shijiazhuang, China.

As an opportunistic pathogen worldwide, Staphylococcus aureus can cause food poisoning and human infections. This study investigated the sequence typing, the penicillin (blaZ) and methicillin (mec) resistance profiles of S. aureus from food samples and food poisoning outbreaks in Shijiazhuang City, and the staphylococcal enterotoxin (SE) types of the S. aureus isolates from food poisoning. A total of 138 foodborne S. aureus isolates were distributed into 8 clonal complexes (CCs) and 12 singletons. CC1, CC5, CC8, CC15, CC97, CC59, CC398, CC88, and CC7 were the predominant CCs of foodborne S. aureus isolates. Moreover, CC59, CC15, and CC5 were the most prevalent CCs in food poisoning outbreaks. SEE was the most commonly detected SE in food poisoning isolates. One hundred thirty-three S. aureus isolates harbored the penicillin-resistant gene blaZ, and nine isolates carried the mec gene. The present study further explained the relationship between S. aureus and foods and food poisoning and indicated the potential risk of S. aureus infection.

Interlaboratory proficiency tests for the detection of staphylococcal enterotoxin type A in food.

Staphylococcal enterotoxins (SEs) are among the leading causes of food intoxications, affecting consumer health even in nanogram (ng) amounts. In the European Union, certain food safety criteria are specified, including the absence of SEs in cheeses, milk powder and whey powder. Until 2019, the analytical reference method used was the European Screening Method, which was replaced by EN ISO 19020. For the official laboratories involved in food control, the German Reference Laboratory for coagulase-positive staphylococci including Staphylococcus aureus organized three interlaboratory proficiency tests (ILPTs) to detect SE type A in food during the years 2013-2018. The selected food products (cream cheese and vanilla pudding) were successfully tested beforehand with regard to easy handling, homogeneity and stability of the added toxin. In 2013, ILPT participants overall were not competent in detecting SE type A in food. The following factors were identified to improve the performance: (i) concentration of sample extract using dialysis; (ii) selection of a sensitive detection kit; and (iii) proper sample handling. By taking these factors into account and instructing and training the laboratories, their competence greatly improved. In 2018, all performance criteria (specificity, sensitivity and accuracy) were >90%, even at very low concentrations of SE type A of approximately 0·01ngg-1 food.

Human Leukemia T-Cell Lines as Alternatives to Animal Use for Detecting Biologically Active Staphylococcal Enterotoxin Type B.

Staphylococcal enterotoxin type B (SEB) is associated with food poisoning. Current methods for the detection of biologically active SEB rely upon its ability to cause emesis when administered to live kittens or monkeys. This technique suffers from poor reproducibility and low sensitivity and is ethically disfavored over concerns for the welfare of laboratory animals. The data presented here show the first successful implementation of an alternative method to live animal testing that utilizes SEB super-antigenic activity to induce cytokine production for specific novel cell-based assays for quantifiable detection of active SEB. Rather than using or sacrificing live animals, we found that SEB can bind to the major histocompatibility complex (MHC) class II molecules on Raji B-cells. We presented this SEB–MHC class II complex to specific Vβ5.3 regions of the human T-cell line HPB-ALL, which led to a dose-dependent secretion of IL-2 that is capable of being quantified and can further detect 10 pg/mL of SEB. This new assay is 100,000 times more sensitive than the ex vivo murine splenocyte method that achieved a detection limit of 1 µg/mL. The data presented here also demonstrate that SEB induced proliferation in a dose-dependent manner for cells obtained by three different selection methods: by splenocyte cells containing 22% of CD4+ T-cells, by CD4+ T-cells enriched to >90% purity by negative selection methods, and by CD4+ T-cells enriched to >95% purity by positive selection methods. The highly enriched and positively isolated CD4+ T-cells with the lowest concentration of antigen-presenting cells (APC) (below 5%) provided higher cell proliferation than the splenocyte cells containing the highest concentration of APC cells.

Highly Sensitive and Specific Detection of Staphylococcal Enterotoxins SEA, SEG, SEH, and SEI by Immunoassay.

Staphylococcal food poisoning (SFP) is one of the most common foodborne diseases worldwide, resulting from the ingestion of staphylococcal enterotoxins (SEs), primarily SE type A (SEA), which is produced in food by enterotoxigenic strains of staphylococci, mainly S. aureus. Since newly identified SEs have been shown to have emetic properties and the genes encoding them have been found in food involved in poisoning outbreaks, it is necessary to have reliable tools to prove the presence of the toxins themselves, to clarify the role played by these non-classical SEs, and to precisely document SFP outbreaks. We have produced and characterized monoclonal antibodies directed specifically against SE type G, H or I (SEG, SEH or SEI respectively) or SEA. With these antibodies, we have developed, for each of these four targets, highly sensitive, specific, and reliable 3-h sandwich enzyme immunoassays that we evaluated for their suitability for SE detection in different matrices (bacterial cultures of S. aureus, contaminated food, human samples) for different purposes (strain characterization, food safety, biological threat detection, diagnosis). We also initiated and described for the first time the development of monoplex and quintuplex (SEA, SE type B (SEB), SEG, SEH, and SEI) lateral flow immunoassays for these new staphylococcal enterotoxins. The detection limits in buffer were under 10 pg/mL (0.4 pM) by enzyme immunoassays and at least 300 pg/mL (11 pM) by immunochromatography for all target toxins with no cross-reactivity observed. Spiking studies and/or bacterial supernatant analysis demonstrated the applicability of the developed methods, which could become reliable detection tools for the routine investigation of SEG, SEH, and SEI.

Staphylococcal Enterotoxin A Production and Inactivation in Bread during the Production Processes

Staphylococcus aureus food poisoning is caused by the intoxication of staphylococcal enterotoxin (SE) produced in foods. Staphylococcal food poisoning is mostly due to staphylococcal enterotoxin type A (SEA) among SEs. There have been many studies on the growth and SEA production of S. aureus in various foods, but few studies in bread. Thus, the SEA production by S. aureus in dough during fermentation and the SEA inactivation in dough during baking were studied in the normal production processes of bread in this study. No growth of S. aureus or SEA production in dough, whose total weight was about 470 g, was observed during the fermentation at 25 and 35℃ for four hr, suggesting that the risk of SEA production in dough during fermentation under these conditions would be negligible. Any SEA injected at 6.0 and 0.56 ng/g in dough could not be detected after 20 and 10 min of baking at 200℃, respectively. These results showed that the baking process, which was completed in 25 min, was enough to inactivate SEA at those doses of SEA in the dough. The results on the production and inactivation of SEA in dough during the production processes in this study would be useful information on microbiological food safety of bread making.

Prediction of detection time of staphylococcal enterotoxin A formed in hydrated batter mix

Staphylococcus aureus food poisoning is caused by the ingestion of staphylococcal enterotoxin (SE) produced in foods and SE type A (SEA) is the most common among many types. While SEA formation in hydrated batter mix can be a potential hazard in the production processes of foods, no information is available. Therefore, the growth kinetics of S. aureus and subsequent SEA formation in hydrated batter mix during storage were studied to estimate the detection time (DT) of SEA. At 30 °C and with different inocula (3–5 log CFU/g), SEA was detected when the population of S. aureus reached 5.5–5.9 log CFU/g in the samples. With an inoculum of 4 log CFU/g and isothermal storage between 14 and 34 °C, SEA was detected when the population reached approximately 6 log CFU/g. Therefore, the time to 6 log CFU/g was chosen to as the DT of SEA in the samples. With a kinetic model predicting the growth of S. aureus in hydrated batter mix, the DTs of SEA stored under both changing and constant temperatures were successfully predicted. These results suggested that the present kinetic model could predict the DT of SEA in hydrated batter mix during storage. Prediction of DT of SEA in batter mix would be useful information to prevent the outbreaks of staphylococcal food poisoning.

Heterogeneity of Molecular Characteristics among Staphylococcus argenteus Clinical Isolates (ST2250, ST2793, ST1223, and ST2198) in Northern Taiwan.

Staphylococcus argenteus is an emerging pathogen that is recognized as non-pigmented Staphylococcus aureus. However, the molecular characteristics of S. argenteus and its virulence factors have not been well studied. The present study analyzed 96 isolates of S. argenteus recovered from blood. Identification of S. argenteus was based on results of MALDI-TOF MS and lacking crtM gene. All 96 isolates were methicillin-susceptible. Multilocus sequence typing (MLST) revealed four sequence types: ST2250 (n = 72), ST2793 (n = 12), ST1223 (n = 10), and ST2198 (n = 2). All 72 ST2250 isolates harbored CRISPR loci with polymorphism of direct repeats and spacers, but no other STs carried CRISPR loci. To date, ST2793 isolates have rarely been reported in other countries. Collagen-binding adhesin gene (cna) and staphylococcal enterotoxin type C (sec) were detected in 12 (100%) and 8 (67%) ST2793 isolates, respectively. ST1223 has been reported as food poisoning pathogens, and enterotoxin gene clusters (egc) were detected in all 10 isolates, while seb gene was detected in three isolates. Two ST2198 isolates carried bone sialoprotein-binding protein gene (bbp), belonging to agr type IV. Our focus on the heterogeneity of molecular characterization in four ST types of S. argenteus revealed that S. argenteus had been isolated as early as 2000. Each ST type of S. argenteus harbors particular genetic markers that may contribute to their virulence.

Microbial Changes in Ready-to-use Packaged Food from Supermarkets and Self-prepared during Storage at 6-9°C

Ready-to-use packaged food sampled from supermarkets was stored at 6-9°C for 0 (fresh), 2 or 4 days. Meat, sea food, fish and vegetables purchased from traditional markets were prepared for use packaged food and well wrapped with PS/PVC film, under the same storage conditions as above. The total aerobic plate counts of all samples increased during storage for 4 days. Coliforms were detected in all samples whereas Salmonella spp. and Staphylococcus aureus were detected in some foods such as fish, meat and sea food. Staphylococcal enterotoxin types found in ready-to-use packaged food from the supermarket and self-prepared foods are different, but types A, B were common types. The microbial changes were similar in different preparation methods(one is "cut then wash", the other is "wash then cut").