title: Biofilm in milking equipment on a dairy farm as a potential source of bulk tank milk contamination with Listeria monocytogenes.
abstract: 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.
authors.affiliation: Department of Population Medicine and Diagnostic Sciences, Cornell University, Ithaca, NY 14853, USA. aal39@cornell.edu
authors.forename: A A
authors.initials: AA
authors.lastname: Latorre
authors.forename: J S
authors.initials: JS
authors.lastname: Van Kessel
authors.forename: J S
authors.initials: JS
authors.lastname: Karns
authors.forename: M J
authors.initials: MJ
authors.lastname: Zurakowski
authors.forename: A K
authors.initials: AK
authors.lastname: Pradhan
authors.forename: K J
authors.initials: KJ
authors.lastname: Boor
authors.forename: B M
authors.initials: BM
authors.lastname: Jayarao
authors.forename: B A
authors.initials: BA
authors.lastname: Houser
authors.forename: C S
authors.initials: CS
authors.lastname: Daugherty
authors.forename: Y H
authors.initials: YH
authors.lastname: Schukken
mesh_terms: D000818:Animals; D018441:Biofilms; D002417:Cattle / Q000382:microbiology; D003612:Dairying / Q000295:instrumentation; D016521:Electrophoresis, Gel, Pulsed-Field; D005506:Food Contamination; D005511:Food Handling; D008089:Listeria monocytogenes / Q000302:isolation & purification; D008855:Microscopy, Electron, Scanning; D008892:Milk / Q000382:microbiology*; D016133:Polymerase Chain Reaction