Biofilm in milking equipment on a dairy farm as a potential source of bulk tank milk contamination with Listeria monocytogenes

A. A. Latorre, J. S. Van Kessel, J. S. Karns, M. J. Zurakowski, A. K. Pradhan, K. J. Boor, B. M. Jayarao, B. A. Houser, C. S. Daugherty, Y. H. Schukken

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131 Scopus citations


The objective of this study was to assess the presence of a Listeria monocytogenes-containing biofilm in milking equipment as a potential source of bulk tank milk contamination on a dairy farm where milk contamination had been previously documented. Samples were collected from milking equipment and milking parlor premises on 4 occasions and analyzed for the presence of L. monocytogenes. Pulsed-field gel electrophoresis (PFGE) typing was conducted on L. monocytogenes isolates from the milking equipment, parlor and storage room floors, bulk tank milk, and in-line milk filters. Pieces from milk meters and rubber liners were obtained to visually assess the presence of a biofilm using scanning electron microscopy. A total of 6 (15%), 4 (25%), and 1 (6%) samples were culture-positive for L. monocytogenes in the first, second, and third sample collection, respectively. Two samples were L. monocytogenes hly PCR-positive but were culture-negative in the fourth sample collection. Combined AscI and ApaI restriction analysis yielded 6 PFGE types for 15 L. monocytogenes isolates obtained from milking equipment, parlor, bulk tank milk, and milk filters. A predominant and persistent PFGE type (PFGE type T) was observed among these L. monocytogenes isolates (9/15 isolates). Scanning electron microscopy of samples from the bottom cover of 2 milk meters showed the presence of individual and clusters of bacteria, mainly associated with surface scratches. The presence of a bacterial biofilm was observed on the bottom covers of the 2 milk meters. Prevention of the establishment of biofilms in milking equipment is a crucial step in fulfilling the requirement of safe, high-quality milk.

Original languageEnglish (US)
Pages (from-to)2792-2802
Number of pages11
JournalJournal of dairy science
Issue number6
StatePublished - Jun 2010

All Science Journal Classification (ASJC) codes

  • Food Science
  • Animal Science and Zoology
  • Genetics


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