Elucidation of Listeria monocytogenes Contamination Routes in Cold-Smoked Salmon Processing Plants Detected by DNA-Based Typing Methods

Abstract

The contamination routes of Listeria monocytogenes in cold-smoked salmon processing plants were investigated by analyzing 3,585 samples from products (produced in 1995, 1996, 1998, and 1999) and processing environments (samples obtained in 1998 and 1999) of two Danish smokehouses. The level of product contamination in plant I varied from 31 to 85%, and no L. monocytogenes was found on raw fish (30 fish were sampled). In plant II, the levels of both raw fish and product contamination varied from 0 to 25% (16 of 185 raw fish samples and 59 of 1,000 product samples were positive for L. monocytogenes). A total of 429 strains of L. monocytogenes were subsequently compared by random amplified polymorphic DNA (RAPD) profiling, and 55 different RAPD types were found. The RAPD types detected on the products were identical to types found on the processing equipment and in the processing environment, suggesting that contamination of the final product (cold-smoked salmon) in both plants (but primarily in plant I) was due to contamination during processing rather than to contamination from raw fish. However, the possibility that raw fish was an important source of contamination of the processing equipment and environment could not be excluded. Contamination of the product occurred in specific areas (the brining and slicing areas). In plant I, the same RAPD type (RAPD type 12) was found over a 4-year period, indicating that an established in-house flora persisted and was not eliminated by routine hygienic procedures. In plant II, where the prevalence of L. monocytogenes was much lower, no RAPD type persisted over long periods of time, and several different L. monocytogenes RAPD types were isolated. This indicates that persistent strains may be avoided by rigorous cleaning and sanitation; however, due to the ubiquitous nature of the organism, sporadic contamination occurred. A subset of strains was also typed by using pulsed-field gel electrophoresis and amplified fragment length polymorphism profiling, and these methods confirmed the type division obtained by RAPD profiling.

Molecular Characterization ofListeria monocytogenesof the Serotype 4b Complex (4b, 4d, 4e) from Two Turkey Processing Plants

“…However, even though the pathogen has been detected and investigated in numerous processing plants, and has on certain occasions been found to persist in a plant over several years (Miettinen et al, 1999;Fonnesbech-Vogel et al, 2001), its ecology and adaptations in the processing plant environment still remain poorly understood. Furthermore, even though a recent report identified isolates with the ribotypes characteristic of ECII in Hispanic-style cheese plants (Kabuki et al, 2004), routine surveys of processing plants for L. monocytogenes have largely failed to document the presence and possible persistence of ECI and ECII isolates.…”

“…Other studies have also documented noticeable variations among plants in prevalence of L. monocytogenes, and of individual strain types (Dauphin et al, 2001;Fonnesbech-Vogel et al, 2001). One can speculate that different environmental conditions in the plants may select for certain strain types.…”

Salmonella Species On Meat Contact Surfaces and Processing Water in Sokoto Main Market and Abattoir, Nigeria

“…Recently, it has been indicated that, many bacterial species are indigenous part of seafood, but they can also be found on the food processing surfaces, where they can subsequently contaminate the products. (8) During the processing of poultry carcasses, microbial contamination inevitably occurs as a consequence of the processing procedures used. At each stage of the process, ample opportunity exists for contamination of the carcass by microorganisms from the processing plant or by cross-contamination from other birds (2).…”

Prevalence of Listeria spp. in freshwater T\s\v(Oncorhynchus my kiss and Carassius gibelio) and the environment offish markets in Northern Greece

“…The prevalence of the pathogen in raw salmon from Chile, Norway and the west coast of the US has been reported to be 8.0%, 21% and 29.5%, respectively (Hoffman et al 2003). In other studies the prevalence of L. monocytogenes has been found to be 7.8% for salmon in the USA (Norton et al 2001) and 7.4% in Denmark (Fonnesbech et al 2001). L. monocytogenes was isolated in rainbow trout from retail markets in USA from 54% of the 74 samples examined (Draughon et al 1999).…”