Staphylococcus aureus growth and enterotoxin production in different types of milk
2012
Janstova, B.Jr., Veterinarni a Farmaceuticka Univ., Brno (Czech Republic). Ustav Hygieny a Technologie Mleka | Necidova, L., Veterinarni a Farmaceuticka Univ., Brno (Czech Republic). Ustav Hygieny a Technologie Mleka | Janstova, B., Veterinarni a Farmaceuticka Univ., Brno (Czech Republic). Ustav Hygieny a Technologie Mleka | Vorlova, L., Veterinarni a Farmaceuticka Univ., Brno (Czech Republic). Ustav Hygieny a Technologie Mleka
The aim of our study was to assess Staphylococcus aureus growth (strains A, B, C) and the time of first detection of staphylococcal enterotoxins (SEs) in different types of milk (raw, pasteurized, UHT) and during different storage conditions (15 and 22 deg C). Milk samples that had tested negative for S. aureus were inoculated with 20-1,400 CFU/mL of the studied strains. Growth patterns were determined by the plate method in accordance with EN ISO 6888-1. Baird-Parker agar medium was used for the detection of S. aureus and the Enzyme Linked Fluorescent Assay (ELFA) used with a miniVIDAS analyzer tested the production of SEs. The results of model experiments showed the dependence of the growth rate and subsequent production of SEs on incubation (storage) temperature, S. aureus strain, and type of milk. A significant finding was that the growth of S. aureus and SEs production in raw milk were inhibited by natural microflora. Therefore, SEs production was not detected in raw milk within 102 hours of storage either at 15 deg C or 22 deg C. The highest risk of SEs production is associated with secondary contamination of pasteurized and UHT milk when stored at room temperature. In this case SEs production was first detected after 12 hours of incubation.
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