Implementation of Statistical Tools To Support Identification and Management of Persistent Listeria monocytogenes Contamination in Smoked Fish Processing Plants

2013 ◽  
Vol 76 (5) ◽  
pp. 796-811 ◽  
Author(s):  
THOMAS J. V. MALLEY ◽  
MATTHEW J. STASIEWICZ ◽  
YRJÖ T. GRÖHN ◽  
SHERRY ROOF ◽  
STEVEN WARCHOCKI ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Food Processing ◽  
Adaptive Sampling ◽  
Poisson Model ◽  
Binomial Test ◽  
Sampling Strategies ◽  
Fish Processing ◽  
Smoked Fish ◽  
Processing Plants ◽  
Food Contact Surface

Listeria monocytogenes persistence in food processing plants is a key source of postprocessing contamination of ready-toeat foods. Thus, identification and elimination of sites where L. monocytogenes persists (niches) is critical. Two smoked fish processing plants were used as models to develop and implement environmental sampling plans (i) to identify persistent L. monocytogenes subtypes (EcoRI ribotypes) using two statistical approaches and (ii) to identify and eliminate likely L. monocytogenes niches. The first statistic, a binomial test based on ribotype frequencies, was used to evaluate L. monocytogenes ribotype recurrences relative to reference distributions extracted from a public database; the second statistic, a binomial test based on previous positives, was used to measure ribotype occurrences as a risk factor for subsequent isolation of the same ribotype. Both statistics revealed persistent ribotypes in both plants based on data from the initial 4 months of sampling. The statistic based on ribotype frequencies revealed persistence of particular ribotypes at specific sampling sites. Two adaptive sampling strategies guided plant interventions during the study: sampling multiple times before and during processing and vector swabbing (i.e., sampling of additional sites in different directions [vectors] relative to a given site). Among sites sampled for 12 months, a Poisson model regression revealed borderline significant monthly decreases in L. monocytogenes isolates at both plants (P = 0.026 and 0.076). Our data indicate elimination of an L. monocytogenes niche on a food contact surface; niches on nonfood contact surfaces were not eliminated. Although our data illustrate the challenge of identifying and eliminating L. monocytogenes niches, particularly at nonfood contact sites in small and medium plants, the methods for identification of persistence we describe here should broadly facilitate science-based identification of microbial persistence.

Tracking of Listeria monocytogenes in Smoked Fish Processing Plants†

2004 ◽  
Vol 67 (2) ◽  
pp. 328-341 ◽  
Author(s):  
JOANNE THIMOTHE ◽  
KENDRA KERR NIGHTINGALE ◽  
KEN GALL ◽  
VIRGINIA N. SCOTT ◽  
MARTIN WIEDMANN
Keyword(s):  
Listeria Monocytogenes ◽  
Environmental Samples ◽  
Control Strategies ◽  
Fish Processing ◽  
Smoked Fish ◽  
Plant Environment ◽  
Fish Samples ◽  
Processing Plants ◽  
Raw Fish ◽  
Contact Surfaces

Four smoked fish processing plants were used as a model system to characterize Listeria monocytogenes contamination patterns in ready-to-eat food production environments. Each of the four plants was sampled monthly for approximately 1 year. At each sampling, four to six raw fish and four to six finished product samples were collected from corresponding lots. In addition, 12 to 14 environmental sponge samples were collected several hours after the start of production at sites selected as being likely contamination sources. A total of 234 raw fish, 233 finished products, and 553 environmental samples were tested. Presumptive Listeria spp. were isolated from 16.7% of the raw fish samples, 9.0% of the finished product samples, and 27.3% of the environmental samples. L. monocytogenes was isolated from 3.8% of the raw fish samples (0 to 10%, depending on the plant), 1.3% of the finished product samples (0 to 3.3%), and 12.8% of the environmental samples (0 to 29.8%). Among the environmental samples, L. monocytogenes was found in 23.7% of the samples taken from drains, 4.8% of the samples taken from food contact surfaces, 10.4% of the samples taken from employee contact surfaces (aprons, hands, and door handles), and 12.3% of the samples taken from other nonfood contact surfaces. Listeria spp. were isolated from environmental samples in each of the four plants, whereas L. monocytogenes was not found in any of the environmental samples from one plant. Overall, the L. monocytogenes prevalence in the plant environment showed a statistically significant (P < 0.0001) positive relationship with the prevalence of this organism in finished product samples. Automated EcoRI ribotyping differentiated 15 ribotypes among the 83 L. monocytogenes isolates. For each of the three plants with L. monocytogenes–positive environmental samples, one or two ribotypes seemed to persist in the plant environment during the study period. In one plant, a specific L. monocytogenes ribotype represented 44% of the L. monocytogenes–positive environmental samples and was also responsible for one of the two finished product positives found in this plant. In another plant, a specific L. monocytogenes ribotype persisted in the raw fish handling area. However, this ribotype was never isolated from the finished product area in this plant, indicating that this operation has achieved effective separation of raw and finished product areas. Molecular subtyping methods can help identify plant-specific L. monocytogenes contamination routes and thus provide the knowledge needed to implement improved L. monocytogenes control strategies.

Prevalence and Survival of Listeria monocytogenes in Danish Aquatic and Fish-Processing Environments

2006 ◽  
Vol 69 (9) ◽  
pp. 2113-2122 ◽  
Author(s):  
CISSE HEDEGAARD HANSEN ◽  
BIRTE FONNESBECH VOGEL ◽  
LONE GRAM
Keyword(s):  
Listeria Monocytogenes ◽  
Food Processing ◽  
Natural Waters ◽  
Minor Importance ◽  
Natural Seawater ◽  
Production Plant ◽  
Fish Processing ◽  
Fish Farms ◽  
Protozoan Grazing ◽  
Processing Plants

Listeria monocytogenes contamination of ready-to-eat food products such as cold-smoked fish is often caused by pathogen subtypes persisting in food-processing environments. The purpose of the present study was to determine whether these L. monocytogenes subtypes can be found in the outside environment, i.e., outside food processing plants, and whether they survive better in the aquatic environment than do other strains. A total of 400 samples were collected from the outside environment, fish slaughterhouses, fish farms, and a smokehouse. L. monocytogenes was not detected in a freshwater stream, but prevalence increased with the degree of human activity: 2% in seawater fish farms, 10% in freshwater fish farms, 16% in fish slaughterhouses, and 68% in a fish smokehouse. The fish farms and slaughterhouses processed Danish rainbow trout, whereas the smokehouse was used for farm-raised Norwegian salmon. No variation with season was observed. Inside the processing plants, the pattern of randomly amplified polymorphic DNA (RAPD) types was homogeneous, but greater diversity existed among isolates from the outside environments. The RAPD type dominating the inside of the fish smokehouse was found only sporadically in outside environments. To examine survival in different environments, L. monocytogenes or Listeria innocua strains were inoculated into freshwater and saltwater microcosms. Pathogen counts decreased over time in Instant Ocean and remained constant in phosphate-buffered saline. In contrast, counts decreased rapidly in natural seawater and fresh water. The count reduction was much slower when the natural waters were autoclaved or filtered (0.2-μm pore size), indicating that the pathogen reduction in natural waters was attributable to a biological mechanism, e.g., protozoan grazing. A low prevalence of L. monocytogenes was found in the outside environment, and the bacteria did not survive well in natural environments. Therefore, L. monocytogenes in the outer environment associated with Danish fish processing is probably of minor importance to the environment inside a fish production plant.

scholarly journals Molecular Studies on the Ecology of Listeria monocytogenes in the Smoked Fish Processing Industry

2001 ◽  
Vol 67 (1) ◽  
pp. 198-205 ◽  
Author(s):  
Dawn M. Norton ◽  
Meghan A. McCamey ◽  
Kenneth L. Gall ◽  
Janet M. Scarlett ◽  
Kathryn J. Boor ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Food Processing ◽  
Environmental Samples ◽  
Raw Materials ◽  
Raw Material ◽  
Fish Processing ◽  
Culture Methods ◽  
Smoked Fish ◽  
Molecular Approaches ◽  
Automated Ribotyping

ABSTRACT We have applied molecular approaches, including PCR-based detection strategies and DNA fingerprinting methods, to study the ecology ofListeria monocytogenes in food processing environments. A total of 531 samples, including raw fish, fish during the cold-smoking process, finished product, and environmental samples, were collected from three smoked fish processing facilities during five visits to each facility. A total of 95 (17.9%) of the samples tested positive forL. monocytogenes using a commercial PCR system (BAX for Screening/Listeria monocytogenes), including 57 (27.7%) environmental samples (n = 206), 8 (7.8%) raw material samples (n = 102), 23 (18.1%) samples from fish in various stages of processing(n = 127), and 7 (7.3%) finished product samples (n= 96). L. monocytogenes was isolated from 85 samples (16.0%) using culture methods. Used in conjunction with a 48-h enrichment in Listeria Enrichment Broth, the PCR system had a sensitivity of 91.8% and a specificity of 96.2%. To track the origin and spread of L. monocytogenes, isolates were fingerprinted by automated ribotyping. Fifteen different ribotypes were identified among 85 isolates tested. Ribotyping data established possible contamination patterns, implicating raw materials and the processing environment as potential sources of finished product contamination. Analysis of the distribution of ribotypes revealed that each processing facility had a unique contamination pattern and that specific ribotypes persisted in the environments of two facilities over time (P ≤ 0.0006). We conclude that application of molecular approaches can provide critical information on the ecology of different L. monocytogenes strains in food processing environments. This information can be used to develop practical recommendations for improved control of this important food-borne pathogen in the food industry.

Listeria monocytogenes Contamination Patterns for the Smoked Fish Processing Environment and for Raw Fish

2003 ◽  
Vol 66 (1) ◽  
pp. 52-60 ◽  
Author(s):  
ADAM D. HOFFMAN ◽  
KENNETH L. GALL ◽  
DAWN M. NORTON ◽  
MARTIN WIEDMANN
Keyword(s):  
Listeria Monocytogenes ◽  
Environmental Contamination ◽  
West Coast ◽  
Environmental Samples ◽  
Raw Materials ◽  
Processing Plant ◽  
Fish Processing ◽  
Smoked Fish ◽  
Fish Samples ◽  
Raw Fish

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.

scholarly journals Phenotypic and genotypic evaluation of Listeria monocytogenes strains isolated from fish and fish processing plants

2019 ◽  
Vol 69 (5) ◽  
pp. 469-482 ◽  
Author(s):  
Krzysztof Skowron ◽  
Natalia Wiktorczyk ◽  
Katarzyna Grudlewska ◽  
Ewa Wałecka-Zacharska ◽  
Zbigniew Paluszak ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Fish Processing ◽  
Processing Plants

scholarly journals Poor Invasion of Trophoblastic Cells but Normal Plaque Formation in Fibroblastic Cells despite actA Deletion in a Group of Listeria monocytogenes Strains Persisting in Some Food Processing Environments

2010 ◽  
Vol 76 (10) ◽  
pp. 3391-3397 ◽  
Author(s):  
Anne Holch ◽  
Caroline Trebbien Gottlieb ◽  
Marianne Halberg Larsen ◽  
Hanne Ingmer ◽  
Lone Gram
Keyword(s):  
Listeria Monocytogenes ◽  
Molecular Subtype ◽  
Stop Codon ◽  
Premature Stop Codon ◽  
Virulence Gene ◽  
Fish Processing ◽  
Trophoblastic Cells ◽  
Processing Plants ◽  
Fibroblastic Cells ◽  
Cell Spread

ABSTRACT We determined mammalian cell invasion and virulence gene (inlA, inlB, and actA) sequences of Listeria monocytogenes strains belonging to a molecular subtype (RAPD 9) that often persists in Danish fish-processing plants. These strains invaded human placental trophoblasts less efficiently than other L. monocytogenes strains, including clinical strains, and they carry a premature stop codon in inlA. Eight of 15 strains, including the RAPD 9 and maternofetal strains, had a 105-nucleotide deletion in actA that did not affect cell-to-cell spread in mouse fibroblasts. The RAPD 9 strains may still be regarded as of low virulence with respect to human listeriosis.

scholarly journals Heavy Metal and Disinfectant Resistance of Listeria monocytogenes from Foods and Food Processing Plants

2012 ◽  
Vol 78 (19) ◽  
pp. 6938-6945 ◽  
Author(s):  
Shakir S. Ratani ◽  
Robin M. Siletzky ◽  
Vikrant Dutta ◽  
Suleyman Yildirim ◽  
Jason A. Osborne ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Listeria Monocytogenes ◽  
Food Processing ◽  
Cadmium Resistance ◽  
Content Type ◽  
Ecological History ◽  
Resistance Determinants ◽  
Processing Plants ◽  
History Of ◽  
Serotype 4B

ABSTRACTThe persistence ofListeria monocytogenesin food processing plants and other ecosystems reflects its ability to adapt to numerous stresses. In this study, we investigated 138 isolates from foods and food processing plants for resistance to the quaternary ammonium disinfectant benzalkonium chloride (BC) and to heavy metals (cadmium and arsenic). We also determined the prevalence of distinct cadmium resistance determinants (cadA1,cadA2, andcadA3) among cadmium-resistant isolates. Most BC-resistant isolates were resistant to cadmium as well. Arsenic resistance was encountered primarily in serotype 4b and was an attribute of most isolates of the serotype 4b epidemic clonal group ECIa. Prevalence of the known cadmium resistance determinants was serotype associated:cadA1was more common in isolates of serotypes 1/2a and 1/2b than 4b, whilecadA2was more common in those of serotype 4b. A subset (15/77 [19%]) of the cadmium-resistant isolates lacked the known cadmium resistance determinants. Most of these isolates were of serotype 4b and were also resistant to arsenic, suggesting novel determinants that may confer resistance to both cadmium and arsenic in these serotype 4b strains. The findings may reflect previously unrecognized components of the ecological history of different serotypes and clonal groups ofL. monocytogenes, including exposures to heavy metals and disinfectants.

Listeria monocytogenes Persistence in Food-Associated Environments: Epidemiology, Strain Characteristics, and Implications for Public Health

2014 ◽  
Vol 77 (1) ◽  
pp. 150-170 ◽  
Author(s):  
V. FERREIRA ◽  
M. WIEDMANN ◽  
P. TEIXEIRA ◽  
M. J. STASIEWICZ
Keyword(s):  
Public Health ◽  
Listeria Monocytogenes ◽  
Food Processing ◽  
Current Knowledge ◽  
Molecular Subtype ◽  
Special Focus ◽  
Quantitative Microbial Risk Assessment ◽  
Genetic Characteristics ◽  
Economic Implications ◽  
Processing Plants

Over the last 10 to 15 years, increasing evidence suggests that persistence of Listeria monocytogenes in food processing plants for years or even decades is an important factor in the transmission of this foodborne pathogen and the root cause of a number of human listeriosis outbreaks. L. monocytogenes persistence in other food-associated environments (e.g., farms and retail establishments) may also contribute to food contamination and transmission of the pathogen to humans. Although L. monocytogenes persistence is typically identified through isolation of a specific molecular subtype from samples collected in a given environment over time, formal (statistical) criteria for identification of persistence are undefined. Environmental factors (e.g., facilities and equipment that are difficult to clean) have been identified as key contributors to persistence; however, the mechanisms are less well understood. Although some researchers have reported that persistent strains possess specific characteristics that may facilitate persistence (e.g., biofilm formation and better adaptation to stress conditions), other researchers have not found significant differences between persistent and nonpersistent strains in the phenotypic characteristics that might facilitate persistence. This review includes a discussion of our current knowledge concerning some key issues associated with the persistence of L. monocytogenes, with special focus on (i) persistence in food processing plants and other food-associated environments, (ii) persistence in the general environment, (iii) phenotypic and genetic characteristics of persistent strains, (iv) niches, and (v) public health and economic implications of persistence. Although the available data clearly indicate that L. monocytogenes persistence at various stages of the food chain contributes to contamination of finished products, continued efforts to quantitatively integrate data on L. monocytogenes persistence (e.g., meta-analysis or quantitative microbial risk assessment) will be needed to advance our understanding of persistence of this pathogen and its economic and public health impacts.

scholarly journals Effect of Atmospheric Pressure Plasma on Listeria monocytogenes Attached to Abiotic Surfaces

2019 ◽  
Vol 82 (2) ◽  
pp. 233-237 ◽  
Author(s):  
VALENTINA ALESSANDRIA ◽  
KALLIOPI RANTSIOU ◽  
MARIA CHIARA CAVALLERO ◽  
LUCA SIMONE COCOLIN
Keyword(s):  
Listeria Monocytogenes ◽  
Food Processing ◽  
Atmospheric Pressure ◽  
Brain Heart Infusion ◽  
Atmospheric Pressure Plasma ◽  
Raw Material ◽  
Pressure Plasma ◽  
Abiotic Surfaces ◽  
Processing Plants ◽  
The Individual

ABSTRACT Listeria monocytogenes can be introduced into food processing plants via raw material of animal or plant origin and can establish endemic populations through formation of biofilms. Biofilms are a continuous source of contamination for food products, and L. monocytogenes cells in biofilms are more resistant to stress and sanitizing agents than are planktonic cells. The use of gas-discharge plasmas may offer a feasible alternative to conventional sanitization methods. Plasmas are a mixture of charged particles, chemically reactive species, and UV radiation and can be used to destroy microorganisms. The purpose of this study was to measure the effectiveness of cold atmospheric pressure plasma (APP) treatments against bacteria attached to a solid surface and to evaluate the individual susceptibility of various L. monocytogenes strains. Attention was focused on the state of the cells after treatment, combining detection by viable counts and quantitative PCR (qPCR). Most of the culturable cells were inactivated after APP treatment, but the qPCR assay targeting the 16S rRNA revealed the presence of injured cells or their entrance into the viable but nonculturable state. These results were at least partly confirmed by a resuscitation experiment. After APP treatment, L. monocytogenes cell suspensions were incubated in brain heart infusion broth; some cells grew in the medium and therefore had survived the treatment. An understanding of the effects of APP on L. monocytogenes can inform the development of sanitation programs incorporating APP for pathogen removal. Methods other than those based of the culturability of the cells should be used to monitor pathogens in food processing plants because cultivation alone may underestimate the actual microbial load.

scholarly journals Conservation and Distribution of the Benzalkonium Chloride Resistance CassettebcrABCin Listeria monocytogenes

2013 ◽  
Vol 79 (19) ◽  
pp. 6067-6074 ◽  
Author(s):  
Vikrant Dutta ◽  
Driss Elhanafi ◽  
Sophia Kathariou
Keyword(s):  
Listeria Monocytogenes ◽  
Food Processing ◽  
Benzalkonium Chloride ◽  
Clinical Environment ◽  
Outbreak Strain ◽  
Content Type ◽  
Chloride Resistance ◽  
Processing Plants ◽  
Hot Dog ◽  
Widespread Dissemination

ABSTRACTAnalysis of a panel of 116Listeria monocytogenesstrains of diverse serotypes and sources (clinical, environment of food processing plants, and food) revealed that all but one of the 71 benzalkonium chloride-resistant (BCr) isolates harboredbcrABC, previously identified on a large plasmid (pLM80) of the 1998-1999 hot dog outbreak strain H7858. In contrast,bcrABCwas not detected among BC-susceptible (BCs) isolates. ThebcrABCsequences were highly conserved among strains of different serotypes, but variability was noted in sequences flankingbcrABC. The majority of the BCrisolates had either the pLM80-type of organization of thebcrABCregion or appeared to harborbcrABCon the chromosome, adjacent to novel sequences. Transcription ofbcrABCwas induced by BC (10 μg/ml) in strains of different serotypes and diversebcrABCregion organization. These findings reveal widespread dissemination ofbcrABCacross BCrL. monocytogenesstrains regardless of serotype and source, while also suggesting possible mechanisms ofbcrABCdissemination acrossL. monocytogenesgenomes.

Sign in / Sign up

Export Citation Format

Share Document