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Enterotoxin-producing Staphylococcus aureus genotype B as a major contaminant in Swiss raw milk cheese.
J Dairy Sci. 2014 Mar; 97(3):1305-12.JD

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.

Authors+Show Affiliations

Agroscope Liebefeld-Posieux Research Station ALP-Haras, Schwarzenburgstrasse 161, 3003 Berne, Switzerland. Electronic address: joerg.hummerjohann@agroscope.admin.ch.Agroscope Liebefeld-Posieux Research Station ALP-Haras, Schwarzenburgstrasse 161, 3003 Berne, Switzerland.Swiss Federal Office of Public Health, Schwarzenburgstrasse 165, 3003 Berne, Switzerland.Agroscope Liebefeld-Posieux Research Station ALP-Haras, Schwarzenburgstrasse 161, 3003 Berne, Switzerland.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

24440268

Citation

Hummerjohann, J, et al. "Enterotoxin-producing Staphylococcus Aureus Genotype B as a Major Contaminant in Swiss Raw Milk Cheese." Journal of Dairy Science, vol. 97, no. 3, 2014, pp. 1305-12.
Hummerjohann J, Naskova J, Baumgartner A, et al. Enterotoxin-producing Staphylococcus aureus genotype B as a major contaminant in Swiss raw milk cheese. J Dairy Sci. 2014;97(3):1305-12.
Hummerjohann, J., Naskova, J., Baumgartner, A., & Graber, H. U. (2014). Enterotoxin-producing Staphylococcus aureus genotype B as a major contaminant in Swiss raw milk cheese. Journal of Dairy Science, 97(3), 1305-12. https://doi.org/10.3168/jds.2013-7643
Hummerjohann J, et al. Enterotoxin-producing Staphylococcus Aureus Genotype B as a Major Contaminant in Swiss Raw Milk Cheese. J Dairy Sci. 2014;97(3):1305-12. PubMed PMID: 24440268.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Enterotoxin-producing Staphylococcus aureus genotype B as a major contaminant in Swiss raw milk cheese. AU - Hummerjohann,J, AU - Naskova,J, AU - Baumgartner,A, AU - Graber,H U, Y1 - 2014/01/17/ PY - 2013/10/25/received PY - 2013/11/24/accepted PY - 2014/1/21/entrez PY - 2014/1/21/pubmed PY - 2015/12/15/medline KW - Staphylococcus aureus KW - mastitis KW - raw milk cheese KW - subtyping SP - 1305 EP - 12 JF - Journal of dairy science JO - J Dairy Sci VL - 97 IS - 3 N2 - 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. SN - 1525-3198 UR - https://www.unboundmedicine.com/medline/citation/24440268/Enterotoxin_producing_Staphylococcus_aureus_genotype_B_as_a_major_contaminant_in_Swiss_raw_milk_cheese_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0022-0302(14)00050-2 DB - PRIME DP - Unbound Medicine ER -