Comparison of Selective Direct Plating Media for Enumeration and Recovery of L. monocytogenes from Cold-process (smoked) Fish

1992 ◽  
Vol 55 (11) ◽  
pp. 905-909 ◽  
Author(s):  
ROHINEE N. PARANJPYE ◽  
GRETCHEN A. PELROY ◽  
MARK E. PETERSON ◽  
FRANK T. POYSKY ◽  
PAUL J. HOLLAND ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Lithium Chloride ◽  
Indicator System ◽  
Water Phase ◽  
Direct Plating ◽  
Selective Media ◽  
Smoked Fish ◽  
Smoked Salmon ◽  
Selective Agar ◽  
Added Salt

Three selective media were evaluated for direct plating recovery and enumeration of Listeria monocytogenes in the presence of high levels of a variety of microorganisms occurring on cold-process (smoked) salmon products. Sliced salmon was brined to contain either no added salt, 3, or 5% water-phase NaCl, or 3 or 5% NaCl plus 140 ppm NaNO2. The slices were packaged in oxygen-permeable film or sealed under vacuum in oxygen-impermeable film, and stored at 10°C or 5°C until total microbial loads reached 106 to 109 CFU/g. Oxford formulation of Listeria selective agar and Lee's modification of Listeria selective agar achieved quantitative recovery of 102 cells per ml of L. monocytogenes strain Scott A in the presence of diluted slurries of these fish containing 104 to 108 CFU/ml of background organisms. A modification of lithium chloride-phenylethanol-moxalactam agar containing an iron-esculin indicator system sometimes failed because of interfering growth by the background microflora.

Parameters for Control of Listeria monocytogenes in Smoked Fishery Products: Sodium Chloride and Packaging Method

1993 ◽  
Vol 56 (11) ◽  
pp. 938-943 ◽  
Author(s):  
MARK E. PETERSON ◽  
GRETCHEN A. PELROY ◽  
ROHINEE N. PARANJPYE ◽  
FRANK T. POYSKY ◽  
JAMIE S. ALMOND ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Sodium Chloride ◽  
Vacuum Packaging ◽  
Water Phase ◽  
Smoked Fish ◽  
Rate Of Growth ◽  
A Cells ◽  
Smoked Salmon ◽  
Nacl Concentration ◽  
Fishery Products

The behavior of Listeria monocytogenes (10 Scott A cells per g) in cold-process (smoked) salmon containing 3, 5, or 6% water-phase NaCl was evaluated during 30 to 40 d storage at 5 or 10°C in either oxygen-permeable film or vacuum-sealed impermeable film. At 10°C, L. monocytogenes grew to 106 to 108 CFU/g by the second week, with no differences attributed to NaCl concentration except for an initial lag in the 6% NaCl samples. Vacuum packaging suppressed growth of L. monocytogenes by 10- to 100-fold in samples with 3 or 5% NaCl. Inhibition related to NaCl concentration was most apparent at 5°C and L. monocytogenes populations were held below 102 CFU/g by 6% NaCl. Growth of a 327 CFU/g inoculum was about 10-fold greater than a 10 CFU/g inoculum at 10°C and 100-fold greater at 5°C. Growth of two strains isolated from naturally contaminated, commercially prepared, cold-smoked fish did not differ from Scott A. The use of sugar in the product did not influence growth of L. monocytogenes. Maximum populations of aerobic microorganisms reached at 5 and 10°C were similar, although the rate of growth was somewhat delayed at 5°C, and some inhibition was shown by 5 and 6% NaCl and by vacuum packaging.

Inactivation of Listeria monocytogenes on Hot-smoked Salmon by the Interaction of Heat and Smoke or Liquid Smoke†

1997 ◽  
Vol 60 (6) ◽  
pp. 649-654 ◽  
Author(s):  
FRANK T. POYSKY ◽  
ROHINEE N. PARANJPYE ◽  
MARK E. PETERSON ◽  
GRETCHEN A. PELROY ◽  
ANNE E. GUTTMAN ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Minimum Temperature ◽  
Soluble Fraction ◽  
Internal Temperature ◽  
Lethal Temperature ◽  
Entire Process ◽  
Smoked Fish ◽  
Liquid Smoke ◽  
Full Strength ◽  
Smoked Salmon

L. monocytogenes was inoculated onto the surface of brined salmon steaks and heat processed in a commercial smokehouse to simulate a hot process for preparing smoked fish. The minimum temperature required for inactivation of L. monocytogenes was 153°F (67.2°C) when generated smoke was applied throughout the entire process. When generated smoke was added only during the last half of the process, L. monocytogenes was recovered from steaks heated to temperatures as high as 176°F (80.0°C). When smoke was not applied during the process, L. monocytogenes survived on steaks heated to internal temperatures between 131°F and 181°F (55.0 to 82.8°C) but was not isolated from steaks heated above 181°F (82.8°C). When liquid smoke CharSol C-l0 was applied as a full-strength (100%) dip before processing, L. monocytogenes was inactivated in samples processed at temperatures as low as 138°F (58.9°C). When liquid smoke l0-Poly or CharSol C-l0 was applied at a concentration of 50%, the lethal temperature was increased to the range of 145 to 150°F (62.8 to 65.6°C). With further dilution of C-l0 to 25% and 10% the inactivation temperatures increased to 156°F (68.9°C) and 163°F (72.8°C). A full-strength dip of CharOil, the oil-soluble fraction of CharSol C-l0, was less effective, and L. monocytogenes survived in salmon steaks processed to an internal temperature of 166°F (74.4°C), the highest temperature tested with this liquid smoke. This study provides evidence that heat alone is not reliable for inactivation of L. monocytogenes during the hot-smoking process. The proper stage and duration of smoke application or proper composition and concentration of liquid smoke in combination with heat are critical for inactivation of the organism.

Inhibition of Listeria monocytogenes in Cold-process (Smoked) Salmon by Sodium Lactate

1994 ◽  
Vol 57 (2) ◽  
pp. 108-113 ◽  
Author(s):  
GRETCHEN A. PELROY ◽  
MARK E. PETERSON ◽  
PAUL J. HOLLAND ◽  
MEL W. EKLUND
Keyword(s):  
Listeria Monocytogenes ◽  
Sodium Chloride ◽  
Sodium Nitrite ◽  
Sodium Lactate ◽  
The Other ◽  
Water Phase ◽  
Smoked Salmon ◽  
Total Inhibition

Comminuted raw salmon containing various concentrations and combinations of sodium lactate, sodium chloride, and sodium nitrite was inoculated with 10 Listeria monocytogenes cells per g (150 cells/15-g sample), vacuum-packaged in oxygen-impermeable film and stored at 5 or 10°C. Samples were examined for growth of L. monocytogenes and total aerobic microorganisms at specific intervals for up to 50 d. Sodium lactate exhibited a concentration-dependent antilisterial effect that was enhanced by nitrite and/or increased concentrations of NaCl. At 5°C, total inhibition of L monocytogenes was achieved for up to 50 d by 2% sodium lactate in combination with 3% water-phase NaCl. At 10°C, total inhibition was achieved for up to 35 d by 3% sodium lactate in combination with 3% water-phase NaCl, or by 2% sodium lactate in combination with 125 ppm sodium nitrite and 3% water-phase NaCl. Sodium lactate and the other additives also inhibited growth of the aerobic microflora but to a lesser degree than L. monocytogenes.

Antilisterial Activity of a Carnobacterium piscicola Isolated from Brazilian Smoked Fish (Surubim [Pseudoplatystoma sp.]) and Its Activity against a Persistent Strain of Listeria monocytogenes Isolated from Surubim

2005 ◽  
Vol 68 (10) ◽  
pp. 2068-2077 ◽  
Author(s):  
VIRGÍNIA F. ALVES ◽  
ELAINE C. P. DE MARTINIS ◽  
MARIA TERESA DESTRO ◽  
BIRTE FONNESBECH VOGEL ◽  
LONE GRAM
Keyword(s):  
Listeria Monocytogenes ◽  
Freshwater Fish ◽  
Random Amplified Polymorphic Dna ◽  
Model Systems ◽  
Fish Products ◽  
Tropical Regions ◽  
Smoked Fish ◽  
Smoked Salmon ◽  
Carnobacterium Piscicola

Data on the prevalence and growth of Listeria monocytogenes in lightly preserved fish products from subtropical and tropical regions are very scarce. Our research describes L. monocytogenes that was detected in 5% of the packages of cold-smoked surubim, a native Brazilian freshwater fish that we analyzed, and shows that the strains isolated were of the same random amplified polymorphic DNA subtype as the strains that were isolated from the same factory 4 years earlier. A bacteriocinogenic strain of Carnobacterium piscicola (strain C2), isolated from vacuum-packed cold-smoked surubim, and two C. piscicola strains, isolated from vacuum-packed, cold-smoked salmon, were capable of limiting or completely inhibiting the growth of an L. monocytogenes (strain V2) isolated from surubim in fish peptone model systems incubated at 10°C. Mono-cultures of L. monocytogenes reached 108 CFU/ml (g), whereas the growth of L. monocytogenes was completely inhibited by C. piscicola C2. The bacteriocinogenic C. piscicola A9b+ and its nonbacteriocinogenic mutant A9b− reduced maximum Listeria levels by 2 to 3 log units. Both bacteriocinogenic C. piscicola strains prevented listerial growth in cold-smoked fish juices (surubim and salmon). Although the carnobacteria grew poorly on cold-smoked surubim at 10°C, the strains were able to reduce maximum Listeria counts by 1 to 3 log units in an artificially inoculated product (surubim). We conclude that Brazilian smoked fish products harbor L. monocytogenes and should be stabilized against the growth of the organism. C. piscicola C2 has the potential for use as a bioprotective culture in surubim and other lightly preserved fish, but further studies are required to optimize its effect.

scholarly journals Validation of a Traditional Italian-Style Salami Manufacturing Process for Control of Salmonella and Listeria monocytogenes†

2006 ◽  
Vol 69 (4) ◽  
pp. 794-800 ◽  
Author(s):  
K. K. NIGHTINGALE ◽  
H. THIPPAREDDI ◽  
R. K. PHEBUS ◽  
J. L. MARSDEN ◽  
A. L. NUTSCH
Keyword(s):  
Listeria Monocytogenes ◽  
Manufacturing Process ◽  
Raw Material ◽  
Cell Recovery ◽  
Recovery Method ◽  
Direct Plating ◽  
Selective Media ◽  
Injured Cell ◽  
Pathogen Populations ◽  
Proximate Analyses

Italian-style salami batter (formulated with pork shoulder) was inoculated with ca. 7.0 log CFU/g of either Salmonella or Listeria monocytogenes. Salami links (55-mm cellulose casings) were fermented at 30°C for 24, 40, or 72 h and then dried to target moisture/protein ratios (MPRs) of 1.9:1 or 1.4:1. Links were sampled after fermentation (24, 40, and 72 h) and after combined fermentation-drying treatments (MPRs of 1.9:1 and 1.4:1 for all fermentation periods), and microbiological and proximate analyses were performed at each sampling. Pathogen populations were enumerated by direct plating on selective agar and by an injured-cell recovery method. When enumerated by the injured-cell recovery method, Salmonella populations were reduced by 1.2 to 2.1 log CFU/g after fermentation alone (24 to 72 h) and by 2.4 to 3.4 log CFU/g when fermentation was followed by drying. Drying to an MPR of 1.4:1 was no more effective than drying to an MPR of 1.9:1 (P > 0.05). When enumerated directly on selective media, Salmonella populations were reduced from 1.6 to 2.4 log CFU/g and from 3.6 to 4.5 log CFU/g for fermentation alone and fermentation followed by drying, respectively. L. monocytogenes populations were reduced by <1.0 log CFU/g following all fermentation and combined fermentation-drying treatments, regardless of the enumeration method. These results suggest that the Italian-style salami manufacturing process evaluated does not adequately reduce high pathogen loads. Processors may thus need to consider supplemental measures, such as raw material specifications and a final heating step, to enhance the lethality of the overall manufacturing process.

Listeria monocytogenes in Smoked Salmon and Other Smoked Fish at Retail in Italy: Frequency of Contamination and Strain Characterization in Products from Different Manufacturers

2017 ◽  
Vol 80 (2) ◽  
pp. 271-278 ◽  
Author(s):  
Vicdalia Aniela Acciari ◽  
Marina Torresi ◽  
Luigi Iannetti ◽  
Silvia Scattolini ◽  
Francesco Pomilio ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Confidence Interval ◽  
Maximum Level ◽  
Restriction Enzymes ◽  
Pulsed Field Gel Electrophoresis ◽  
Strain Characterization ◽  
Smoked Fish ◽  
Smoked Salmon ◽  
Italian Market ◽  
Different Levels

ABSTRACT Seven hundred seventy-eight samples of packaged smoked fish (774 smoked salmon and 4 smoked swordfish) on sale in Italy, from 50 different manufacturers located in 12 European Union countries, were purchased from the Italian market between May and December 2011. The surface temperatures of the samples on sale ranged from 0 to 13°C (3.4 ± 1.5°C, mean ± SD). Six hundred eighty (87.4%) of 778 samples were stored at ≤4°C. One hundred fifty-seven samples (20.2%, 95% confidence interval 17.5 to 23.1%) were contaminated by Listeria monocytogenes, with 26 samples (3.3%, 95% confidence interval 2.3 to 4.8%) at levels >100 CFU/g. The maximum level of contamination was 1.3 ×106 CFU/g. The differences in the level of contamination of smoked fish between countries (χ2 = 91.54, P < 0.05) and manufacturers (χ2 = 193.22, P < 0.05) were significant. The frequency of detection for products from different manufacturing premises ranged from 0 to 76.9%. Serotyping by serological agglutination revealed that the main serotypes detected were 1/2a (65.3%) and 1/2b (22.4%). Pulsed-field gel electrophoresis typing with restriction enzymes AscI and ApaI yielded 36 pulsotypes from 144 isolates, clustering into 17 groups. Eight main pulsotypes accounted for 70.8% of the isolates. Three of the main pulsotypes were exclusively from products of a single manufacturer. In general, products from the same manufacturer showed genetic homogeneity, with one strongly prevalent pulsotype. Different manufacturers usually showed very different levels of contamination of the final product, confirming the importance of the management of process hygiene for controlling L. monocytogenes contamination.

Spray Method for Recovery of Heat-Injured Salmonella Typhimurium and Listeria monocytogenes

2012 ◽  
Vol 75 (10) ◽  
pp. 1867-1872 ◽  
Author(s):  
KYEONG-HWAN BACK ◽  
SANG-OH KIM ◽  
KI-HWAN PARK ◽  
MYUNG-SUB CHUNG ◽  
DONG-HYUN KANG
Keyword(s):  
Listeria Monocytogenes ◽  
Salmonella Typhimurium ◽  
Recovery Rate ◽  
Skim Milk ◽  
Selective Media ◽  
Spray Method ◽  
Selective Agar ◽  
Overlay Method ◽  
Peptone Water ◽  
Pathogen Recovery

Selective agar is inadequate for supporting recovery of injured cells. During risk assessment of certain foods, both injured and noninjured cells must be enumerated. In this study, a new method (agar spray method) for recovering sublethally heat-injured microorganisms was developed and used for recovery of heat-injured Salmonella Typhimurium and Listeria monocytogenes. Molten selective agar was applied as an overlay to presolidified nonselective tryptic soy agar (TSA) by spray application. Heat-injured cells (55°C for 10 min in 0.1% peptone water or 55°C for 15 min in sterilized skim milk) were inoculated directly onto solidified TSA. After a 2-h incubation period for cell repair, selective agar was applied to the TSA surface with a sprayer, and the plates were incubated. The recovery rate for heat-injured Salmonella Typhimurium and L. monocytogenes with the spray method was compared with the corresponding rates associated with TSA alone, selective media alone, and the conventional overlay method (selective agar poured on top of resuscitated cells grown on TSA and incubated for 2 h). No significant differences (P > 0.05) were found in pathogen recovery obtained with TSA, the overlay method, and the spray method. However, a lower recovery rate (P < 0.05) was obtained for isolation of injured cells on selective media. Overall, these results indicate that the agar spray method is an acceptable alternative to the conventional overlay method and is a simpler and more convenient approach to recovery and detection of injured cells.

scholarly journals Identification and serotyping of Listeria monocytogenes, isolated from various salmon products, sold in retail market in Lithuania

2021 ◽  
Vol 10 (3) ◽  
Author(s):  
Ineta Simonavičienė ◽  
Gintarė Zakariene ◽  
Aušra Lozoraitytė ◽  
Gintarė Zaborskienė ◽  
Gediminas Gerulis ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Multiplex Pcr ◽  
Local Market ◽  
Microbiological Analysis ◽  
Retail Market ◽  
Fish Products ◽  
Smoked Fish ◽  
Smoked Salmon ◽  
Study Results ◽  
Fish Product

Cold smoked salmon products (belly flaps, pieces, fillet, and loin) obtained from the retail market in Lithuania were tested for the presence of L. monocytogenes. It was found that contamination of the cold smoked fish products with Listeria spp. depends on the type of the product. Contamination with listeria in salmon belly flaps was 7.5 times higher than in the loin (P<0.05), 1.8 times higher than in the pieces (P<0.05) and 30 times higher than in the fillet (P<0.05). Microbiological analysis showed that 32.5% (P<0.05) of the fish product samples were infected with L. monocytogenes, while multiplex PCR confirmed 31.25% positive samples (P<0.01). According to the study results, L. monocytogenes strains were divided into two serotypes: 4b (94.6%) and 1/2a (5.4%). High contamination of the products with Listeria spp. showed that cold smoked salmon products, sold in local market, can be a reason of human listeriosis in Lithuania.

scholarly journals Transcriptomic Analysis of the Adaptation of Listeria monocytogenes to Growth on Vacuum-Packed Cold Smoked Salmon

2015 ◽  
Vol 81 (19) ◽  
pp. 6812-6824 ◽  
Author(s):  
Silin Tang ◽  
Renato H. Orsi ◽  
Henk C. den Bakker ◽  
Martin Wiedmann ◽  
Kathryn J. Boor ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Molecular Mechanisms ◽  
Growth Parameters ◽  
Differential Expression Analysis ◽  
Foodborne Pathogen ◽  
Brain Heart Infusion ◽  
Enrichment Analysis ◽  
Water Phase ◽  
Content Type ◽  
Smoked Salmon

ABSTRACTThe foodborne pathogenListeria monocytogenesis able to survive and grow in ready-to-eat foods, in which it is likely to experience a number of environmental stresses due to refrigerated storage and the physicochemical properties of the food. Little is known about the specific molecular mechanisms underlying survival and growth ofL. monocytogenesunder different complex conditions on/in specific food matrices. Transcriptome sequencing (RNA-seq) was used to understand the transcriptional landscape ofL. monocytogenesstrain H7858 grown on cold smoked salmon (CSS; water phase salt, 4.65%; pH 6.1) relative to that in modified brain heart infusion broth (MBHIB; water phase salt, 4.65%; pH 6.1) at 7°C. Significant differential transcription of 149 genes was observed (false-discovery rate [FDR], <0.05; fold change, ≥2.5), and 88 and 61 genes were up- and downregulated, respectively, in H7858 grown on CSS relative to the genes in H7858 grown in MBHIB. In spite of these differences in transcriptomes under these two conditions, growth parameters forL. monocytogeneswere not significantly different between CSS and MBHIB, indicating that the transcriptomic differences reflect howL. monocytogenesis able to facilitate growth under these different conditions. Differential expression analysis and Gene Ontology enrichment analysis indicated that genes encoding proteins involved in cobalamin biosynthesis as well as ethanolamine and 1,2-propanediol utilization have significantly higher transcript levels in H7858 grown on CSS than in that grown in MBHIB. Our data identify specific transcriptional profiles ofL. monocytogenesgrowing on vacuum-packaged CSS, which may provide targets for the development of novel and improved strategies to controlL. monocytogenesgrowth on this ready-to-eat food.

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