Longitudinal Monitoring of Listeria monocytogenes Contamination Patterns in a Farmstead Dairy Processing Facility

Abstract

Contamination of dairy products with Listeria monocytogenes is a concern because multiple human listeriosis outbreaks have been linked to contaminated cheese and dairy products. Dairy production on farmstead operations may be a particular concern because L. monocytogenes is also an animal pathogen that can be shed by ruminants with and without clinical symptoms; physical proximity between production animal and dairy processing facilities may thus provide a higher risk for introduction of L. monocytogenes into the dairy production process. To better understand the risks of L. monocytogenes contamination associated with farmstead dairy production, samples from a farmstead dairy processing operation and the milking barn of the directly adjacent dairy sheep operation were tested for L. monocytogenes over a 3-yr period. Prevalence of L. monocytogenes for samples collected on the farm (n = 85) and the dairy production facility (n = 674) was 9.4 and 2.7%, respectively. Molecular subtyping using automated EcoRI ribotyping of L. monocytogenes isolates revealed that distinct subtypes were associated with the dairy production facility and the farm's milking parlor. Although a total of 5 and 4 different ribotypes were identified among isolates obtained from the dairy production facility and the milking parlor, respectively, only 1 ribotype (DUP-1030A) was isolated from both. Different ribotypes were predominant among isolates from the dairy production facility (ribotype DUP-1052A, representing 15 of 18 isolates) and the farm's milking parlor (ribotype DUP-1039A, representing 4 of 8 isolates); each of these ribotypes appeared to persist over time in the respective area. Our data support that i) in farmstead dairy processing facilities, L. monocytogenes present on the farm can largely be prevented from being introduced into the processing facility; and ii) L. monocytogenes can persist on farm and in processing areas, providing a potential high-risk source for contamination. Preventing cross contamination between dairy production and processing facilities and control of persistent L. monocytogenes are thus critical to assuring the microbial safety of farmstead dairy products.

Review. Dairy farm management and production practices associated with the presence of Listeria monocytogenes in raw milk and beef

“…Contamination of the processing environment results from on-farm Listeria contamination from silage, dairy cattle and raw milk (Arimi et al, 1997). Processors must specifically enforce restrictions and procedures that prevent cross-contamination between the dairy farm environment and the processing environment (Ho et al, 2007b) as well as between raw and processed food.…”

“…Some specific subtypes of L. monocytogenes can also persist for extended periods in many different food processing environments , including dairy food processing plants (Vazquez-Villanueva et al, 2010;Latorre et al, 2011). In the dairy plant, Listeria can persist in a variety of sites, although it is most frequently found in moist environments or areas with condensed or standing water or milk, including drains, floors, coolers, conveyors and case washing areas (Arimi et al, 1997;Ho et al, 2007b;Fox et al, 2009).…”

“…However, contamination seems in most cases to come from the production environment (cross-contamination), rather than from the raw milk itself; consequently, producing safe raw milk cheese depends upon the conditions and practices under which it is produced (Ho et al, 2007b;Fox et al, 2011). Soft cheeses made from raw milk under uncontrolled conditions are considered to be high-risk foods for susceptible individuals.…”

Permanent colonization of creek sediments, creek water and limnic water plants by fourListeriaspecies in low population densities

“…Also, ready-to-eat food or dairy products that have not been pasteurized, such as raw milk cheese or smoked salmon pose significant risks to consumers. Due to its importance as a food-borne pathogen, numerous studies on this genus deal with the occurrence and tracing of L. monocytogenes in food processing plants and in farm environments [17,[25][26][27][28][29][30].…”

Isolation of <i>Listeria monocytogenes</i> from Peridomestic Birds and Captive Wild Animals

“…Listeria species are saprophytes having environmental reservoirs and they may enter into the food chain through various routes. Infection of L. monocytogenes is mainly acquired through contaminated food; several studies have highlighted the incidence of this pathogen in foods and food-processing environment 21,22 . However, not may studies have been conducted on non-conventional sources of L. monocytogenes like the role of wild animals and birds.…”