Biofilm in milking equipment on a dairy farm as a potential source of bulk tank milk contamination with Listeria monocytogenes.
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.
Latorre
A A
AA
Department of Population Medicine and Diagnostic Sciences, Cornell University, Ithaca, NY 14853, USA. aal39@cornell.edu
Van Kessel
J S
JS
Karns
J S
JS
Zurakowski
M J
MJ
Pradhan
A K
AK
Boor
K J
KJ
Jayarao
B M
BM
Houser
B A
BA
Daugherty
C S
CS
Schukken
Y H
YH
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