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Research article2010Peer reviewed

Occurrence of foodborne pathogens and characterization of Staphylococcus aureus in cheese produced on farm-dairies

Rosengren, Åsa; Fabricius, Ane; Guss, Bengt; Sylvén, Susanne; Lindqvist, Roland

Abstract

The objective of this study was to address knowledge gaps identified in an earlier risk assessment of Staphylococcus aureus and raw milk cheese. A survey of fresh and short-time ripened cheeses produced on farm-dairies in Sweden was conducted to investigate the occurrence and levels of S. aureus, Listeria monocytogenes and Escherichia coil, to characterize S. aureus isolates with special emphasis on enterotoxin genes, antibiotic resistance, bio-typing and genetic variation, and to collect information related to production practices. In general, the hygienic quality of farm-dairy cheeses appeared to be of an acceptable microbiological quality, e.g. L monocytogenes and staphylococcal enterotoxin were not detected in cheese samples. However, E. colt and enterotoxigenic S. aureus were frequently found in raw milk cheeses and sometimes at levels that are of concern, especially in fresh cheese. Interestingly, levels in raw milk fresh cheese were significantly lower when starter cultures were used. Up to five S. aureus colonies per cheese, if possible, were characterized and about 70% of isolates carried one or more enterotoxin genes, most common were sec and sea. The Ovine biotype (73%) was most common among isolates from goat milk cheese and the Human biotype (60%) from cow milk cheese. Of all isolates, 39% showed decreased susceptibility to penicillin, but the proportion of isolates from cows' cheese (66%) compared to isolates from goats' cheese (27%) was significantly higher. S. aureus isolates with different properties were detected in cheese from the same farm and, sometimes even the same cheese. Isolates with the same pulsed-field gel electrophoresis (PFGE)-pattern were detected on geographically distant dairies. This indicates that multiple sources and routes of contamination are important. To improve the safety of these products efforts to raise awareness of the importance of hygiene barriers and raw milk quality as well as improved process control can be suggested, e.g. use of starter cultures and monitoring of fermentation with a pH-meter. For future safety assessments, a better understanding of factors determining toxin production in these cheeses is needed. (C) 2010 Elsevier B.V. All rights reserved.

Keywords

Survey; Raw milk cheese; Food safety; Listeria monocytogenes; Escherichia coil; Staphylococcus aureus

Published in

International Journal of Food Microbiology
2010, Volume: 144, number: 2, pages: 263-269
Publisher: ELSEVIER SCIENCE BV

      SLU Authors

      • Associated SLU-program

        AMR: Bacteria

        Sustainable Development Goals

        Ensure healthy lives and promote well-being for all at all ages
        End hunger, achieve food security and improved nutrition and promote sustainable agriculture

        UKÄ Subject classification

        Food Science

        Publication identifier

        DOI: https://doi.org/10.1016/j.ijfoodmicro.2010.10.004

        Permanent link to this page (URI)

        https://res.slu.se/id/publ/60499