Foodborne pathogens in unpasteurized milk in Sweden

Research output: Contribution to journalArticle

Abstract

Raw milk may be a risk for public health if it is contaminated with zoonotic pathogens. To study the prevalence
in unpasteurized milk from Swedish farms, bovine and small ruminant dairy farms were sampled. Since the
sampling method and transport conditions may influence the outcome of analyses, efforts were made to optimize
the methodology. Culturing of bacteria was done from in-line milk filters collected from the milk pipe at the
point where it enters the milk bulk tank at the farms and this way of sampling was compared to sampling bulk
tank milk (BTM) directly. Analysing milk filters were found to be superior to analysing BTM directly. Conditions
for transport of milk filter samples were further improved by the addition of Cary Blair transport medium, which
significantly increased the number of positive samples for pathogenic bacteria. The isolation of several foodborne
pathogens from milk filters was demonstrated. The prevalence of samples with Staphylococcus aureus was
71% and 64%, and Listeria spp. 21% and 29% from dairy cow and goat/sheep farms, respectively. Campylobacter
jejuni, Yersinia enterocolitica and verotoxigenic Escherichia coli (VTEC) O157 were detected in 9%, 2% and 2% of
samples from bovine milk, respectively.
We conclude that the choice of sampling method and sample handling influence the results of bacterial
culturing. From the results of this study, we strongly recommend to sample in-line milk filters instead of BTM
directly and to use Cary Blair medium during transport, especially if the samples are to be analysed for
Campylobacter spp. and/or Listeria spp. The findings also show that unpasteurized milk from Swedish farms
occasionally contain bacteria with zoonotic potential.

Details

Authors
  • Karin Artursson
  • Jenny Schelin
  • Susanne Thisted Lambertz
  • Ingrid Hansson
  • Eva Olsson Engvall
Organisations
External organisations
  • Swedish National Veterinary Institute
  • Swedish University of Agricultural Sciences
  • National Food Agency
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Microbiology in the medical area
  • Food Engineering
Original languageEnglish
Pages (from-to)120-127
JournalInternational Journal of Food Microbiology
Volume284
Early online date2018 May 19
Publication statusPublished - 2018
Publication categoryResearch
Peer-reviewedYes