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.

Increased In Vitro Adherence and On-Farm Persistence of Predominant and Persistent Listeria monocytogenes Strains in the Milking System

“…Listeria monocytogenes has been isolated from many locations within dairy farms, including feces (32,39,40), animal drinking water (29,37,40), feeds or feed components (37,39), and milking equipment (29,30). A potential link between animal production systems and human listeriosis cases exists, as was suggested by previous studies that described the presence of L. monocytogenes ribotypes (39) or pulsed-field gel electrophoresis (PFGE) types (3,17) from farms that matched those observed for isolates from human listeriosis cases.…”

Diversity and biofilm-forming capability of bacteria recovered from stainless steel pipes of a milk-processing dairy plant

“…The presence of biofilms is a widespread phenomenon in many ecosystems, including dairy plants (Latorre et al 2010). Biofilm development takes place when planktonic cells adhere to a surface in a reversible and nonspecific manner due to electrostatic interactions and begin to secrete a complex extracellular matrix.…”

“…For all these reasons, the removal of biofilm-embedded microorganisms continues to be a major challenge in dairy industry. A large number of food spoilage and/or pathogenic bacteria, including Enterococcus faecalis, Pseudomonas spp., Klebsiella spp., Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, and others, have already been associated with biofilms from dairy niches (Brooks and Flint 2008;Latorre et al 2010;Sharma and Anand 2002).…”

“…The presence of biofilms in equipment and tools of milk-processing plants, such as bends in pipes, gaskets, floors, milk handling devices, etc., has been well documented (Brooks and Flint 2008). Biofilms are considered as a source of microbial contamination leading to food spoilage, shelf life reduction, and are also considered as a potential way of pathogen transmission (Brooks and Flint 2008;Latorre et al 2010). Bacteria embedded in a biofilm have been considered as more resistant to cleaning and sanitizing chemicals than the corresponding planktonic cells (Anand and Singh 2013;Peng et al 2002).…”

Survival of Listeria monocytogenes in Soil Requires AgrA-Mediated Regulation

“…The pathogen is largely spread in the environment. It has been isolated from water systems (2-4), vegetation (5), soil (6)(7)(8), farms (9)(10)(11)(12), food industries (13)(14)(15), and the feces of animals (16)(17)(18). Environmental adaptation requires that the cell have the ability to integrate environmental cues in order to adapt its physiology to the surrounding conditions through the regulation of gene expression.…”