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Hennekinne JA, Ostyn A, Guillier F, Gohier M, Messio S, Dragacci S, Krys S, Lombard B, Bauer MCC, Alves P, Bauer MC, Blanco-Vidal C, Desfargues C, De Reu K, Eckner K, Economides C, Ferrini AM, Gaillard N, Genot P, Gornard S, Guiliani L, Hummerjohann J, In’t Velt P, Jacobs-Reistma W, Ladstatter J, Montourcy G, Pires-Gomes C, Pittet JL, Rola J, Rubert E, Srete-Lancz Z. Interlaboratory Validation of the Vidas SET2 Kit for Detection of Staphylococcal Enterotoxins in Milk Products. J AOAC Int 2019. [DOI: 10.1093/jaoac/90.3.756] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Abstract
An earlier intralaboratory validation study based on the EN ISO 16140 Standard conducted by the Community Reference Laboratory for coagulase-positive staphylococci including Staphylocococcus aureus showed that, after an extraction step using dialysis concentration, the Vidas SET2 detection kit could be used to screen staphylococcal enterotoxins in milk and milk products. In order to fully validate Vidas SET2, an interlaboratory study was organized. Six freeze-dried samples and 3 ready-to-use concentrated extracts were analyzed by 21 laboratories according to the method, including a detection with Vidas SET2. Results did not show false-positive or -negative results. Accordance and concordance parameters were equal to 100%, corresponding to a concordance odds ratio of 1. This interlaboratory study confirmed the satisfactory outcome of the preliminary tests and of the intralaboratory study performed previously. The Vidas SET2 detection kit can be used as a method for the detection of staphylococcal enterotoxins in milk and milk products as well as the Transia Plate SET detection kit in the European screening method for official control purposes, after an extraction step followed by dialysis concentration.
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Affiliation(s)
- Jacques-Antoine Hennekinne
- French Agency for Food Safety, Laboratory for Study and Research on Quality of Food and on Food Processes (AFSSA-LERQAP), Toxins, Organic Pollutants, and Pesticides Unit, National and Community Reference Laboratory for Coagulase-Positive Staphylococci, Including Staphylococccus aureus and Their Toxins, 23 Ave du Gnral De Gaulle, 94706 Maisons-Alfort Cedex, France
| | - Annick Ostyn
- French Agency for Food Safety, Laboratory for Study and Research on Quality of Food and on Food Processes (AFSSA-LERQAP), Toxins, Organic Pollutants, and Pesticides Unit, National and Community Reference Laboratory for Coagulase-Positive Staphylococci, Including Staphylococccus aureus and Their Toxins, 23 Ave du Gnral De Gaulle, 94706 Maisons-Alfort Cedex, France
| | - Florence Guillier
- French Agency for Food Safety, Laboratory for Study and Research on Quality of Food and on Food Processes (AFSSA-LERQAP), Toxins, Organic Pollutants, and Pesticides Unit, National and Community Reference Laboratory for Coagulase-Positive Staphylococci, Including Staphylococccus aureus and Their Toxins, 23 Ave du Gnral De Gaulle, 94706 Maisons-Alfort Cedex, France
| | - Martine Gohier
- French Agency for Food Safety, Laboratory for Study and Research on Quality of Food and on Food Processes (AFSSA-LERQAP), Toxins, Organic Pollutants, and Pesticides Unit, National and Community Reference Laboratory for Coagulase-Positive Staphylococci, Including Staphylococccus aureus and Their Toxins, 23 Ave du Gnral De Gaulle, 94706 Maisons-Alfort Cedex, France
| | - Sabine Messio
- French Agency for Food Safety, Laboratory for Study and Research on Quality of Food and on Food Processes (AFSSA-LERQAP), Toxins, Organic Pollutants, and Pesticides Unit, National and Community Reference Laboratory for Coagulase-Positive Staphylococci, Including Staphylococccus aureus and Their Toxins, 23 Ave du Gnral De Gaulle, 94706 Maisons-Alfort Cedex, France
| | - Sylviane Dragacci
- French Agency for Food Safety, Laboratory for Study and Research on Quality of Food and on Food Processes (AFSSA-LERQAP), Toxins, Organic Pollutants, and Pesticides Unit, National and Community Reference Laboratory for Coagulase-Positive Staphylococci, Including Staphylococccus aureus and Their Toxins, 23 Ave du Gnral De Gaulle, 94706 Maisons-Alfort Cedex, France
| | - Sophie Krys
- French Agency for Food Safety, Laboratory for Study and Research on Quality of Food and on Food Processes (AFSSA-LERQAP), Toxins, Organic Pollutants, and Pesticides Unit, National and Community Reference Laboratory for Coagulase-Positive Staphylococci, Including Staphylococccus aureus and Their Toxins, 23 Ave du Gnral De Gaulle, 94706 Maisons-Alfort Cedex, France
| | - Bertrand Lombard
- French Agency for Food Safety, Laboratory for Study and Research on Quality of Food and on Food Processes (AFSSA-LERQAP), Toxins, Organic Pollutants, and Pesticides Unit, National and Community Reference Laboratory for Coagulase-Positive Staphylococci, Including Staphylococccus aureus and Their Toxins, 23 Ave du Gnral De Gaulle, 94706 Maisons-Alfort Cedex, France
| | - M C C Bauer
- French Agency for Food Safety, Laboratory for Study and Research on Quality of Food and on Food Processes (AFSSA-LERQAP), Toxins, Organic Pollutants, and Pesticides Unit, National and Community Reference Laboratory for Coagulase-Positive Staphylococci, Including Staphylococccus aureus and Their Toxins, 23 Ave du Gnral De Gaulle, 94706 Maisons-Alfort Cedex, France
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Hummerjohann J, Naskova J, Baumgartner A, Graber HU. Enterotoxin-producing Staphylococcus aureus genotype B as a major contaminant in Swiss raw milk cheese. J Dairy Sci 2014; 97:1305-12. [PMID: 24440268 DOI: 10.3168/jds.2013-7643] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Accepted: 11/24/2013] [Indexed: 11/19/2022]
Abstract
The objective of this study was to characterize Staphylococcus aureus isolates from Swiss raw milk cheeses that had been found to be contaminated with coagulase-positive staphylococci and to estimate the frequency of the various genotypes, in particular the mastitis-associated Staph. aureus genotype B (GTB). The isolates were also tested for staphylococcal enterotoxin (SE) genes and other virulence factors. From 623 coagulase-positive staphylococci isolated from 78 contaminated raw milk cheeses, 609 were found to be Staphylococcus aureus. Genotyping of all Staph. aureus isolates was performed by PCR amplification of the 16S-23S rRNA intergenic spacer region, as this method was used previously to differentiate between mastitis subtypes associated with their clinical outcome. In total, 20 different genotypes were obtained and the 5 most frequently occurring genotypes were distributed in 6.4% or more of the samples. The enterotoxin-producing Staph. aureus GTB, known for its high contagiousness and increased pathogenicity in Swiss mastitis herds, was found to be the most abundant subtype at the sample level (71.8%) as well as among the isolates (62.0%). A subset of 107 isolates of the different genotypes were analyzed for the presence of SE genes and revealed 9 different SE gene patterns, with sed being most frequently detected and 26% being PCR-negative for SE genes. Almost all isolates of the major contaminant GTB contained the SE gene pattern sed, sej, ser, with half of them additionally carrying sea. Production of SE in vitro was consistent with the SE genes detected in most of the cases; however, some isolated GTB did not produce SEA. Staphylococcus aureus Protein A (spa) typing revealed 30 different subtypes and most GTB isolates belonged to the bovine spa type t2953; GTB/t2953 was linked among other subtypes to SE production in cheese and staphylococcal intoxication cases. Furthermore, 1 of the 623 isolates was a methicillin-resistant Staph. aureus, which was an seh-carrying Staph. aureus spa type tbl 0635 (non-GTB). We conclude that control and reduction of enterotoxigenic Staph. aureus GTB in dairy herds in Switzerland will not only prevent economic losses at the farm level but also improve the safety of raw milk cheeses; distribution of methicillin-resistant Staph. aureus via raw milk cheese is of less concern.
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Affiliation(s)
- J Hummerjohann
- Agroscope Liebefeld-Posieux Research Station ALP-Haras, Schwarzenburgstrasse 161, 3003 Berne, Switzerland.
| | - J Naskova
- Agroscope Liebefeld-Posieux Research Station ALP-Haras, Schwarzenburgstrasse 161, 3003 Berne, Switzerland
| | - A Baumgartner
- Swiss Federal Office of Public Health, Schwarzenburgstrasse 165, 3003 Berne, Switzerland
| | - H U Graber
- Agroscope Liebefeld-Posieux Research Station ALP-Haras, Schwarzenburgstrasse 161, 3003 Berne, Switzerland
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Peng S, Hummerjohann J, Stephan R, Hammer P. Short communication: heat resistance of Escherichia coli strains in raw milk at different subpasteurization conditions. J Dairy Sci 2013; 96:3543-6. [PMID: 23548287 DOI: 10.3168/jds.2012-6174] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Accepted: 02/11/2013] [Indexed: 11/19/2022]
Abstract
A commonly applied treatment of raw milk to reduce bacterial loads is the short-time application of heat at subpasteurization levels under continuous flow, generally referred to as thermization, because this method retains some of the beneficial properties of raw milk. In a previous study, Escherichia coli strains exhibiting increased thermotolerance were found, demanding investigations into their ability to survive thermization. Nine E. coli strains, including 4 Shiga toxin-producing E. coli (STEC) strains, were investigated for their reduction during a thermization treatment in raw milk using a pilot-plant pasteurizer to reflect typically applied commercial conditions. Six of the 9 E. coli strains, including the 4 STEC strains, were similarly inactivated at 60, 62.5, and 65°C, whereas increased thermotolerance was observed for 3 E. coli strains. All strains were reduced to <2 log10 at 60 and 62.5°C within 25s. At 65°C, 6 of 9 E. coli strains were reduced by at least 5 log10 after 25s, whereas at 67.5°C, such a reduction was observed for 8 strains. A much higher thermotolerance was found for E. coli strain FAM21805. For some E. coli strains, time-temperature combinations above 65°C were required to obtain a substantial reduction during a thermization treatment.
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Affiliation(s)
- S Peng
- Institute for Food Safety and Hygiene, University of Zurich, 8057 Zurich, Switzerland
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Hummerjohann J, Laudenbach S, Rétey J, Leisinger T, Kertesz MA. The sulfur-regulated arylsulfatase gene cluster of Pseudomonas aeruginosa, a new member of the cys regulon. J Bacteriol 2000; 182:2055-8. [PMID: 10715018 PMCID: PMC101934 DOI: 10.1128/jb.182.7.2055-2058.2000] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A gene cluster upstream of the arylsulfatase gene (atsA) in Pseudomonas aeruginosa was characterized and found to encode a putative ABC-type transporter, AtsRBC. Mutants with insertions in the atsR or atsB gene were unable to grow with hexyl-, octyl-, or nitrocatecholsulfate, although they grew normally with other sulfur sources, such as sulfate, methionine, and aliphatic sulfonates. AtsRBC therefore constitutes a general sulfate ester transport system, and desulfurization of aromatic and medium-chain-length aliphatic sulfate esters occurs in the cytoplasm. Expression of the atsR and atsBCA genes was repressed during growth with sulfate, cysteine, or thiocyanate. No expression of these genes was observed in the cysB mutant PAO-CB, and the ats genes therefore constitute an extension of the cys regulon in this species.
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Affiliation(s)
- J Hummerjohann
- Institute of Microbiology, Swiss Federal Institute of Technology, ETH-Zentrum, CH-8092 Zürich, Switzerland
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Dierks T, Miech C, Hummerjohann J, Schmidt B, Kertesz MA, von Figura K. Posttranslational formation of formylglycine in prokaryotic sulfatases by modification of either cysteine or serine. J Biol Chem 1998; 273:25560-4. [PMID: 9748219 DOI: 10.1074/jbc.273.40.25560] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Eukaryotic sulfatases carry an alpha-formylglycine residue that is essential for activity and is located within the catalytic site. This formylglycine is generated by posttranslational modification of a conserved cysteine residue. The arylsulfatase gene of Pseudomonas aeruginosa also encodes a cysteine at the critical position. This protein could be expressed in active form in a sulfatase-deficient strain of P. aeruginosa, thereby restoring growth on aromatic sulfates as sole sulfur source, and in Escherichia coli. Analysis of the mature protein expressed in E. coli revealed the presence of formylglycine at the expected position, showing that the cysteine is also converted to formylglycine in a prokaryotic sulfatase. Substituting the relevant cysteine by a serine codon in the P. aeruginosa gene led to expression of inactive sulfatase protein, lacking the formylglycine. The machinery catalyzing the modification of the Pseudomonas sulfatase in E. coli therefore resembles the eukaryotic machinery, accepting cysteine but not serine as a modification substrate. By contrast, in the arylsulfatase of Klebsiella pneumoniae a formylglycine is found generated by modification of a serine residue. The expression of both the Klebsiella and the Pseudomonas sulfatases as active enzymes in E. coli suggests that two modification systems are present, or that a common modification system is modulated by a cofactor.
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Affiliation(s)
- T Dierks
- Institut für Biochemie und Molekulare Zellbiologie, Abt. Biochemie II, Universität Göttingen, Gosslerstrasse 12d, 37073 Göttingen, Germany.
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