The occurrence, transmission, virulence and antibiotic resistance of Listeria monocytogenes in fish processing plant

Reliable data on the sources of Listeria monocytogenes contamination in cold-smoked fish processing are crucial in designing effective intervention strategies. Environmental samples (n = 512) and raw fish samples (n = 315) from two smoked fish processing facilities were screened for L. monocytogenes, and all isolates were subtyped by automated ribotyping to examine the relationship between L. monocytogenes contamination from raw materials and that from environmental sites. Samples were collected over two 8-week periods in early spring and summer. The five types of raw fish tested included lake whitefish, sablefish, farm-raised Norwegian salmon, farm-raised Chilean salmon, and feral (wild-caught) salmon from the U.S. West Coast. One hundred fifteen environmental samples and 46 raw fish samples tested positive for L. monocytogenes. Prevalence values for environmental samples varied significantly (P < 0.0001) between the two plants; plant A had a prevalence value of 43.8% (112 of 256 samples), and plant B had a value of 1.2% (3 of 256 samples). For plant A, 62.5% of drain samples tested positive for L. monocytogenes, compared with 32.3% of samples collected from other environmental sites and 3.1% of samples collected from food contact surfaces. Ribotyping identified 11 subtypes present in the plant environments. Multiple subtypes, including four subtypes not found on any raw fish, were found to persist in plant A throughout the study. Contamination prevalence values for raw fish varied from 3.6% (sablefish) to 29.5% (U.S. West Coast salmon), with an average overall prevalence of 14.6%. Sixteen separate L. monocytogenes subtypes were present on raw fish, including nine that were not found in the plant environment. Our results indicate a disparity between the subtypes found on raw fish and those found in the processing environment. We thus conclude that environmental contamination is largely separate from that of incoming raw materials and includes strains persisting, possibly for years, within the plant. Operational and sanitation procedures appear to have a significant impact on environmental contamination, with both plants having similar prevalence values for raw materials but disparate contamination prevalence values for the environmental sites. We also conclude that regular L. monocytogenes testing of drains, combined with molecular subtyping of the isolates obtained, allows for efficient monitoring of persistent L. monocytogenes contamination in a processing plant.

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The possible effect of a sanitization program on intraspecies differentiation of Listeria monocytogenes strains isolated from a fish processing plant

International Journal of Hygiene and Environmental Health ◽

10.1078/1438-4639-00243 ◽

2003 ◽

Vol 206 (6) ◽

pp. 583-590 ◽

Cited By ~ 5

Author(s):

Dagmara Mędrala ◽

Waldemar Dąbrowski ◽

Urszula Czekajło-Kołodziej ◽

Elżbieta Daczkowska-Kozon ◽

Anna Koronkiewicz ◽

...

Keyword(s):

Listeria Monocytogenes ◽

Processing Plant ◽

Fish Processing

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Biofilm Formation and Resistance to Benzalkonium Chloride in Listeria monocytogenes Isolated from a Fish Processing Plant

Journal of Food Protection ◽

10.4315/0362-028x.jfp-12-225 ◽

2013 ◽

Vol 76 (7) ◽

pp. 1179-1186 ◽

Cited By ~ 38

Author(s):

HIROMI NAKAMURA ◽

KOH-ICHI TAKAKURA ◽

YOSHIAKI SONE ◽

YASUYUKI ITANO ◽

YOSHIKAZU NISHIKAWA

Keyword(s):

Listeria Monocytogenes ◽

Benzalkonium Chloride ◽

Extracellular Polymeric Substances ◽

Foodborne Pathogen ◽

Maximum Activity ◽

Processing Plant ◽

Fish Processing ◽

Glucose Content ◽

Transient Strain ◽

Life Threatening Illness

Listeria monocytogenes is a foodborne pathogen that causes the potentially life-threatening illness listeriosis. Previously, a few clones of L. monocytogenes persisting in a cold-smoked fish processing plant were isolated from the plant's products continuously. To evaluate the role of biofilms in the persistence of L. monocytogenes strains specific to this plant, the abilities of the persistent strain (PS) and transient strain (TS) of L. monocytogenes found in this plant to form biofilms were compared, as was resistance to the sanitizing effects of benzalkonium chloride (BC). The PS produced more biofilm than the TS in 48 h. The half-maximal effective concentration (EC50), the BC concentration at which the ATP bioluminescence of each bacterial strain decreased by 50% relative to its maximum activity, was about 150-fold higher in the PS than in the TS. In contrast, when these values were measured in organisms in a planktonic state, the EC50 of the PS was only 2.2-fold higher than that of the TS. Extracellular polymeric substances (EPS) were extracted from biofilms, and the glucose content of these biofilms was determined with the phenol–sulfuric acid method to estimate the quantity of EPS. The total amount of EPS in the PS biofilm was higher than that in the TS biofilm. These findings suggest that the PS produces greater amounts of biofilm and EPS than the TS, which results in greater resistance of the PS to disinfectants. The persistence of the strain in the fish processing plant might be attributable to these properties.

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A Contingency Locus inprfAin a Listeria monocytogenes Subgroup Allows Reactivation of the PrfA Virulence Regulator during Infection in Mice

Applied and Environmental Microbiology ◽

10.1128/aem.02708-10 ◽

2011 ◽

Vol 77 (10) ◽

pp. 3478-3483 ◽

Cited By ~ 15

Author(s):

Toril Lindbäck ◽

Indira Secic ◽

Liv Marit Rørvik

Keyword(s):

Listeria Monocytogenes ◽

Phase Variation ◽

Direct Repeat ◽

Pulsed Field Gel Electrophoresis ◽

Processing Plant ◽

Fish Processing ◽

Reversible Inactivation ◽

Content Type ◽

Virulence Assay ◽

Virulence Regulator

ABSTRACTA nonhemolyticListeria monocytogenesstrain isolated from a fish processing plant was avirulent in a plaque-forming assay and in a subcutaneous mouse virulence assay. However, it showed 60% lethality (9/15 mice) when 109CFU were intraperitoneally injected into mice. HemolyticL. monocytogenesbacteria were recovered from liver and spleen of the deceased mice, and the pulsed-field gel electrophoresis patterns were indistinguishable for the nonhemolytic and the hemolytic isolates. Sequencing ofprfAfrom the nonhemolytic strain revealed a duplication of 7 bp in the helix-turn-helix region, resulting in a truncated PrfA protein. We propose that the direct repeat of 7 bp causes a reversible inactivation ofprfAand that slipped-strand mispairing regulates the phase variation in hemolytic activity and virulence. NonhemolyticL. monocytogenesstrains with identical duplications inprfAwere isolated from several sources in France, as well as in Norway, suggesting that the reversible inactivation described in this study is not an isolated event.

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Sodium Chloride Enhances Adherence and Aggregation and Strain Variation Influences Invasiveness of Listeria monocytogenes Strains

Journal of Food Protection ◽

10.4315/0362-028x-70.3.592 ◽

2007 ◽

Vol 70 (3) ◽

pp. 592-599 ◽

Cited By ~ 51

Author(s):

ANNE JENSEN ◽

MARIANNE H. LARSEN ◽

HANNE INGMER ◽

BIRTE FONNESBECH VOGEL ◽

LONE GRAM

Keyword(s):

Listeria Monocytogenes ◽

Growth Patterns ◽

Genetic Lineage ◽

Processing Plant ◽

Fish Processing ◽

Plastic Surface ◽

Processing Plants ◽

Different Temperatures ◽

Moderate Salinity ◽

Similar Growth

Some subtypes of Listeria monocytogenes can persist in the food-processing industry, but the reasons for such persistence are not known. In the present study, 10 strains of L. monocytogenes representing known persistent randomly amplified polymorphic DNA (RAPD) types from fish processing plants were compared to eight strains of different RAPD type and origin (clinical, food, and animal). All 18 strains of L. monocytogenes had similar growth patterns at different temperatures (5 or 37°C) or different salinities (0.5 or 5% NaCl), and all strains formed a thin layer of adhered cells on a plastic surface when cultured in tryptone soya broth (TSB) with a total of 1% glucose. Many ready-to-eat foods, such as cold-smoked fish, contain NaCl at concentrations of 2 to 5%, and NaCl is present in the processing environment. Adding NaCl to TSB changed the adhesion patterns of all strains, and all adhered better when NaCl was added. Also, the addition of NaCl caused a marked aggregation of 13 of the strains; however, 5 of the 18 strains did not aggregate in the presence of up to 5% NaCl. The aggregates stuck to the plastic surface, and this occurred in all but one of the persistent RAPD types. Four strains represented one particular RAPD type that has been isolated as a persistent RAPD type in several fish processing plants for up to 10 years. Because this RAPD type often can contaminate fish products, it is important to address its potential virulence. The 18 strains differed markedly in their ability to invade Caco-2 cells, and the four strains representing the universal persistent RAPD type were the least invasive (102 to 103 CFU/ml), whereas other strains invaded Caco-2 cells at levels of 104 to 105 CFU/ml. Five of the 18 strains belonged to the genetic lineage 1 and were the most invasive. Although the most commonly isolated persistent RAPD type was low invasive, it is important to understand why moderate salinity facilitates aggregation and biofilm formation, for this understanding can be beneficial in developing procedures to reduce processing plant contamination.

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Mathematical Model of Listeria monocytogenes Cross-Contamination in a Fish Processing Plant

Journal of Food Protection ◽

10.4315/0362-028x-67.12.2688 ◽

2004 ◽

Vol 67 (12) ◽

pp. 2688-2697 ◽

Cited By ~ 24

Author(s):

RENATA IVANEK ◽

YRJÖ T. GRÖHN ◽

MARTIN WIEDMANN ◽

MARTIN T. WELLS

Keyword(s):

Mathematical Model ◽

Listeria Monocytogenes ◽

Food Products ◽

Raw Material ◽

Processing Plant ◽

Cross Contamination ◽

Fish Processing ◽

Food Contact ◽

Food Contact Surfaces ◽

Contact Surfaces

Listeriosis is a foodborne disease caused by the bacterium Listeria monocytogenes. The food industry and government agencies devote considerable resources to reducing contamination of ready-to-eat foods with L. monocytogenes. Because inactivation treatments can effectively eliminate L. monocytogenes present on raw materials, postprocessing cross-contamination from the processing plant environment appears to be responsible for most L. monocytogenes food contamination events. An improved understanding of cross-contamination pathways is critical to preventing L. monocytogenes contamination. Therefore, a plant-specific mathematical model of L. monocytogenes cross-contamination was developed, which described the transmission of L. monocytogenes contamination among food, food contact surfaces, employees' gloves, and the environment. A smoked fish processing plant was used as a model system. The model estimated that 10.7% (5th and 95th percentile, 0.05% and 22.3%, respectively) of food products in a lot are likely to be contaminated with L. monocytogenes. Sensitivity analysis identified the most significant input parameters as the frequency with which employees' gloves contact food and food contact surfaces, and the frequency of changing gloves. Scenario analysis indicated that the greatest reduction of the within-lot prevalence of contaminated food products can be achieved if the raw material entering the plant is free of contamination. Zero contamination of food products in a lot was possible but rare. This model could be used in a risk assessment to quantify the potential public health benefits of in-plant control strategies to reduce cross-contamination.

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Molecular Typing To Trace Listeria monocytogenes Isolated from Cold-Smoked Fish to a Contamination Source in a Processing Plant

Journal of Food Protection ◽

10.4315/0362-028x-69.4.835 ◽

2006 ◽

Vol 69 (4) ◽

pp. 835-841 ◽

Cited By ~ 17

Author(s):

HIROMI NAKAMURA ◽

YUKA TOKUDA ◽

AYUMI SONO ◽

TOMOKA KOYAMA ◽

JUN OGASAWARA ◽

...

Keyword(s):

Listeria Monocytogenes ◽

Molecular Typing ◽

Pulsed Field Gel Electrophoresis ◽

Processing Plant ◽

Fish Processing ◽

Contamination Source ◽

Processing Equipment ◽

Smoked Fish ◽

Different Types ◽

Raw Fish

In this study, Listeria monocytogenes contamination in a cold-smoked fish processing plant in Osaka, Japan, was examined from 2002 to 2004. A total of 430 samples were collected and divided into five categories: raw fish, materials during processing, processing equipment, environment, and finished products. A total of 59 finished products were examined throughout this study. L. monocytogenes was isolated from four of these samples during summer and autumn but was not found during winter or spring. During the warmer seasons, L. monocytogenes was more prevalent on processing equipment, especially slicing machines (8 of 54 samples in summer and autumn versus 1 of 50 samples in winter and spring). L. monocytogenes was not detected on whole skins removed from 23 frozen raw fish. L. monocytogenes strains isolated from 56 samples were characterized by serotyping, pulsed-field gel electrophoresis, and three PCR-based methods. Seventy-seven L. monocytogenes strains were recognized as contaminants of the samples: 2 distinguishable strains were identified in each of 13 samples, 3 strains were identified in 2 samples, 5 strains were identified in 1 sample, and the other 40 strains were identified in 40 samples. Combining the results from these techniques, 77 strains were classified into 13 different types. Three of these types prevailed throughout the plant, and two of the three were also isolated from final products. The DNA subtype found in the product was also found on the slicing machines. Our findings suggest that the slicing machines at this plant were the source of the product contamination. Implementing an appropriate cleaning regime for the slicing machines was effective in preventing contamination.

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