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Iacumin L, Cappellari G, Pellegrini M, Basso M, Comi G. Analysis of the Bioprotective Potential of Different Lactic Acid Bacteria Against Listeria monocytogenes in Cold-Smoked Sea Bass, a New Product Packaged Under Vacuum and Stored at 6 ± 2°C. Front Microbiol 2021; 12:796655. [PMID: 34987492 PMCID: PMC8721034 DOI: 10.3389/fmicb.2021.796655] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2021] [Accepted: 11/22/2021] [Indexed: 11/21/2022] Open
Abstract
The aim of the work was to monitor the presence of Listeria monocytogenes in cold-smoked fish products (trout, salmon, and sea bass) marketed in Italy. Cold-smoked sea bass is a new product that has not yet been commercialized and was collected from the production facility. Monitoring data have shown that cold-smoked products can be contaminated by L. monocytogenes, the presence of which has been highlighted mainly by enrichment culture (presence in 25 g). The isolated Listeria were serotyped and belonged mainly to low-virulence serotypes (1/2c), followed by serotypes 1/2a, 1/2b, and 4b. Furthermore, considering the ability of L. monocytogenes to grow in these products due to their chemical-physical characteristics (pH > 6.0, Aw > 0.97) and long shelf life at 4°C, an additional aim was to verify the activity of different bioprotective starters, including Lactilactobacillus sakei (LAK-23, Sacco srl, Via Alessandro Manzoni 29/A, 22071 Cadorago, CO, Italy), Carnobacterium spp., Lacticaseibacillus casei (SAL 106), and Lacticaseibacillus paracasei (SAL 211), in cold-smoked sea bass. All starters were bacteriocin producers. For this experiment, smoked sea bass samples were intentionally inoculated with a mixture of three different strains of L. monocytogenes and of each starter culture. After inoculation, the smoked sea bass were vacuum-packed and stored at 6 ± 2°C for 60 days, simulating the typical abuse storage temperature of markets and home refrigerators. At 0, 15, 30, 45, and 60 days, the sea bass samples were analyzed to evaluate the effectiveness of the starters against L. monocytogenes. Listeria monocytogenes growth was prevented only by the addition of the LAK-23 starter. Indeed, at the end of the shelf life, the amount of L. monocytogenes observed was similar to that in the inoculum. Consequently, the use of this starter can allow the inclusion of cold-smoked sea bass or smoked fish products in category 1.3 of Regolamento CE 2073/2005, which are products that do not support the growth of this microorganism. Finally, the activity of the LAK-23 starter did not produce an off flavor or off odor in the smoked sea bass.
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Affiliation(s)
| | | | | | | | - Giuseppe Comi
- Department of Agricultural, Food, Environmental and Animal Science, Università degli Studi di Udine, Udine, Italy
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Capita R, Prieto M, Mereghetti L, Alonso-Calleja C. Characterisation of Listeria monocytogenes Isolates from Poultry by Serotyping and Phage Typing. FOOD SCI TECHNOL INT 2016. [DOI: 10.1177/1082013205051264] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
With the aim of improving the knowledge of Listeria monocytogenestypes distributed in poultry, isolates collected from a hundred eviscerated and refrigerated chicken carcasses from four different slaughterhouse plants in northwest Spain were characterised by serotyping and phage typing. Forty-two phage patterns were observed. Eight phage patterns (43, 43/387, 43/387/4477/1652 and 43/19/387/575 for strains of serogroup 1/2 and 107, 108/107/47, 2389 and 2389/3274 for strains of serogroup 4) were the most common. Thus, thirty strains (56.60% of phage typeable strains) showed the above-mentioned or indistinguishable (1 major phage reaction differences for serogroup 1/2 strains or 2 major differences for serogroup 4) patterns. A wide distribution of some L. monocytogenesphage types was observed because different chicken carcasses (including carcasses from different slaughterhouses) were contaminated with the same or indistinguishable L. monocytogenesphage types. Besides, more than one type (serogroup or phage type) of L. monocytogeneswas detected in 43.75% of positive samples. This finding emphasised the usefulness of subtyping several Listeria monocytogenesisolates from the same food sample in epidemiological studies.
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Affiliation(s)
- R. Capita
- Departmentof Food Hygiene and Food Technology, University of León, Spain
| | - M. Prieto
- Departmentof Food Hygiene and Food Technology, University of León, Spain
| | - L. Mereghetti
- Laboratoryof Bacteriology, Medicine Faculty, University FranÁois Rabelais, Tours, France
| | - C. Alonso-Calleja
- Departmentof Food Hygiene and Food Technology, University of León, Spain
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Kim C, Stein RA, Pao S. Comparison of the Microbial Quality of Lamb and Goat Meat Acquired from Internet and Local Retail Markets. J Food Prot 2015; 78:1980-7. [PMID: 26555521 DOI: 10.4315/0362-028x.jfp-15-026] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This study was conducted to evaluate the microbial quality of lamb and goat meat sold through local (Virginia) and Internet (U. S.) retail markets. A total of 134 frozen meat products consisting of locally purchased lamb ground (LLG) and lamb chops and Internet-procured lamb ground, goat ground, lamb chops (ILC), goat chops (IGC), lamb stew, and goat stew were tested. Significantly higher levels of aerobic mesophiles, psychrotrophs, and coliforms were found in the meat locally acquired than in the meat procured from the Internet. Similar average prevalence (27%) of Escherichia coli was observed regardless of market source. Ground meat had significantly high levels and prevalence of mesophiles, psychrotrophs, coliforms, and Listeria spp. One sample of LLG contained Campylobacter, and one sample of IGC contained Salmonella. Listeria spp. were present in 23 to 40% and 17 to 80% of samples from local and Internet markets, respectively. Pulsed-field gel electrophoresis (PFGE) of isolated E. coli strains revealed brand specificity and genomic diversity. No isolate from different brands and market sources had matching PFGE profiles. The average price of Internet meat ($23.4/kg) was about 1.2 times higher than the price of local meat, except for ILC, whose price was 2.7 times higher. This study revealed differences in microbial quality of lamb and goat meat based on market source; thus, meat products should be handled carefully regardless of market source because of the presence of high microbial levels and the high prevalence of pathogens.
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Affiliation(s)
- Chyer Kim
- Agricultural Research Station, Virginia State University, Petersburg, Virginia 23806, USA.
| | - Roslyn A Stein
- Agricultural Research Station, Virginia State University, Petersburg, Virginia 23806, USA
| | - Steven Pao
- Department of Food Science and Nutrition, Jordan College of Agricultural Science and Technology, Fresno State University, Fresno, California 93740, USA
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Mataragas M, Bellio A, Rovetto F, Astegiano S, Decastelli L, Cocolin L. Risk-based control of food-borne pathogens Listeria monocytogenes and Salmonella enterica in the Italian fermented sausages Cacciatore and Felino. Meat Sci 2015; 103:39-45. [DOI: 10.1016/j.meatsci.2015.01.002] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Revised: 12/02/2014] [Accepted: 01/05/2015] [Indexed: 11/28/2022]
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5
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Pao S, Ettinger MR. Comparison of the microbial quality of ground beef and ground beef patties from internet and local retail markets. J Food Prot 2009; 72:1722-6. [PMID: 19722408 DOI: 10.4315/0362-028x-72.8.1722] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This study evaluated the microbial quality of ground beef and ground beef patties sold at local (Virginia) and Internet (U.S.) retail markets. A total of 152 ground beef products, consisting of locally purchased raw ground beef (LRG) and frozen beef patties (LFP) and Internet-procured frozen ground beef (IFG) and frozen beef patties (IFP), were tested. Results showed that LFP had significantly lower levels of aerobic mesophiles, psychrotrophs, and coliforms than LRG, IFG, and IFP. Furthermore, IFG had greater numbers of Escherichia coli than LRG and LFP. No sample was contaminated with E. coli 0157: H7, but one duplicate set of summer LFP samples contained Salmonella. Listeria spp. were present in 25 and 29% of samples from local and Internet markets, respectively. About 5.0, 11.1, 10.5, and 7.9% of LRG, LFP, IFG, and IFP samples were contaminated with L. monocytogenes. This study identified differences in microbial quality between local and Internet products. Careful handling and thorough cooking of ground beef products, regardless of market source, are recommended to prevent foodborne illness.
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Affiliation(s)
- S Pao
- Virginia State University, Agricultural Research Station, P.O. Box 9061, Petersburg, Virginia, USA.
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Lianou A, Sofos JN. A review of the incidence and transmission of Listeria monocytogenes in ready-to-eat products in retail and food service environments. J Food Prot 2007; 70:2172-98. [PMID: 17900099 DOI: 10.4315/0362-028x-70.9.2172] [Citation(s) in RCA: 259] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Contamination of ready-to-eat products with Listeria monocytogenes may occur at several stages before consumption. Accessibility to the public and relatively limited control interventions at retail and food service establishments (compared with the processing sector of the food industry) and the lack of a specific regulatory framework increase the likelihood of introduction of this pathogen into some foods in these establishments. This review is a compilation of available information on the incidence and transmission of L. monocytogenes through ready-to-eat products at the retail and food service level. The potential transmission of L. monocytogenes within retail and food service operations has been indicated in epidemiological investigations and by survey data. Potential sources of the organism in these operations include the environment, food handlers, and incoming raw ingredients or processed products that have become contaminated after the lethality treatment at the manufacturing facility. L. monocytogenes may be present at retail and food service establishments in various ready-to-eat products, both prepackaged and those packaged in the store, and occasionally at high concentrations. This issue dictates the need for development and application of effective control measures, and potential control approaches are discussed here. Good manufacturing practices, appropriate cleaning, sanitation and hygiene programs, and temperature control required for prevention or inhibition of growth of the pathogen to high levels are critical for control of L. monocytogenes in the retail and food service sector. A comprehensive food safety system designed to be functional in retail and food service operations and based on the philosophy of hazard analysis and critical control point systems and a series of sound prerequisite programs can provide effective control of L. monocytogenes in these environments. However, competent delivery of food safety education and training to retail and food service managers and food handlers must be in place for successful implementation of such a system.
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Affiliation(s)
- Alexandra Lianou
- Center for Red Meat Safety, Department of Animal Sciences, Colorado State University, Fort Collins, Colorado 80523-1171, USA
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Martín B, Jofré A, Garriga M, Hugas M, Aymerich T. Quantification of Listeria monocytogenes in fermented sausages by MPN-PCR method. Lett Appl Microbiol 2004; 39:290-5. [PMID: 15287877 DOI: 10.1111/j.1472-765x.2004.01580.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIMS To combine the principles of most-probable-number (MPN) statistics and the conventional PCR technique to enumerate Listeria monocytogenes in fermented sausages. METHODS AND RESULTS A simple method to enumerate L. monocytogenes in fermented sausages was developed and compared with direct plating in Palcam agar. Species-specific MPN-PCR, but not direct plating, made the enumeration of L. monocytogenes possible in all assayed samples. CONCLUSIONS MPN-PCR proved to be a rapid and reliable method for enumerating L. monocytogenes in fermented sausages, including low contaminated samples. SIGNIFICANCE AND IMPACT OF THE STUDY This MPN-PCR technique may facilitate the enumeration of L. monocytogenes for routine analyses in fermented sausages without excessive work.
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Affiliation(s)
- B Martín
- Meat Technology Center, IRTA, Granja Camps i Armet, Girona, Spain
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8
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Capita R, Alonso-Calleja C. Comparison of different most-probable-number methods for enumeration of Listeria in poultry. J Food Prot 2003; 66:65-71. [PMID: 12540183 DOI: 10.4315/0362-028x-66.1.65] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
To estimate levels of Listeria spp. in poultry and to select the most appropriate enumeration method for routine analysis, 40 naturally contaminated retail chicken carcasses were tested in Ponferrada (León, N.W. Spain) using the direct plate count technique and various most-probable-number (MPN) designs (UVM I [University of Vermont modified Listeria enrichment broth], Fraser enrichment broth, or both were used in 3-, 5-, and 10-tube MPN techniques). MPN estimation was obtained from the number of tubes with Listeria confirmed (after streaking on PALCAM and modified Oxford agars: "true" MPN) and from the number of dark Fraser broth tubes ("predictive" MPN). Samples were analyzed in duplicate. Low levels of Listeria were found (< 110 CFU/g). The direct plate count technique was totally ineffective for enumerating Listeria in poultry. The single-step (UVM I) and the two-step (UVM I-Fraser) MPN methods gave comparable estimations and a low number of significantly discrepant predictions. Using a single-step method with Fraser broth, lower true MPNs were obtained. The number of tubes used (3, 5, or 10) did not have a substantial influence on the results. Similar estimations, highly correlated (r = 0.538 to 0.968; P < 0.001), were found with (true MPN) and without (predictive MPN) plating confirmation when using the two-step MPN method. The statistical evaluation of the differential character of Fraser broth as part of the two-step MPN method showed high sensitivity (87.5 to 92.5%), specificity (95.2 to 98.6%), efficiency (94.2 to 97.6%), and predictive values (73.6 to 89.9% for a positive test and 98.0 to 98.9% for a negative test). Taking into account these results, we suggest the convenience of using a 3- or 5-tube two-step (UVM I-Fraser) MPN method with estimations obtained from the number of tubes with darkening, without confirmation, in order to achieve great savings in time and money.
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Affiliation(s)
- Rosa Capita
- Area de Nutrición y Bromatología, Escuela Superior y Técnica de Ingeniería Agraria (ESTIA), Universidad de León (Campus de Ponferrada), Avda. Astorga, s/n, 24400-Ponferrada (León), Spain.
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Meylheuc T, Giovannacci I, Briandet R, Bellon-Fontaine MN. Comparison of the cell surface properties and growth characteristics of Listeria monocytogenes and Listeria innocua. J Food Prot 2002; 65:786-93. [PMID: 12030289 DOI: 10.4315/0362-028x-65.5.786] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Growth kinetics and physicochemical surface properties were compared for three Listeria strains with differing degrees of virulence: L. monocytogenes LO28; its isogenic, nonhemolytic mutant L. monocytogenes Bof415; and a nonvirulent species, L. innocua (strain Lin9). The influences of growth stage (mid-exponential phase, early stationary phase, and mid-stationary phase) and culture temperature (20 and 37 degrees C) were assessed by determining the electrical properties and the hydrophobic-hydrophilic and Lewis acid-base characteristics of the three strains. L. innocua, although taxonomically very similar to L. monocytogenes, exhibited physicochemical surface properties that differed significantly from those of L. monocytogenes LO28 and L. monocytogenes Bof415. Indeed, under our experimental conditions, L. innocua cells presented a more marked electronegative character (particularly when cultured at 20 degrees C), as well as greater variability in their Lewis acid-base characteristics as a function of temperature and growth stage. Furthermore, the growth kinetics of the three strains revealed the onset of a decay phase after 16 h of culture at 37 degrees C for the L monocytogenes Bof415 mutant. All of these results demonstrate that under our experimental conditions, the growth and/or physicochemical characteristics of the slightly pathogenic or nonpathogenic Listeria strains (Bof415 and Lin9) differed from those of the virulent strain (L. monocytogenes LO28). Consequently, the use of Listeria strains recognized as nonvirulent appeared to provide a model that was not fully suitable for simulating the bioadhesive behavior of the pathogenic strains involved in foodborne diseases.
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Affiliation(s)
- Thierry Meylheuc
- Unité de Recherche en Bioadhésion et Hygiène des Matériaux, Institut National de la Recherche Agronomique, Massy, France.
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Passos MHC, Kuaye AY. Influence of the formulation, cooking time and final internal temperature of beef hamburgers on the destruction of Listeria monocytogenes. Food Control 2002. [DOI: 10.1016/s0956-7135(01)00080-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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11
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Capita R, Alonso-Calleja C, Moreno B, García-Fernandez MC. Occurrence of Listeria species in retail poultry meat and comparison of a cultural/immunoassay for their detection. Int J Food Microbiol 2001; 65:75-82. [PMID: 11322703 DOI: 10.1016/s0168-1605(00)00497-9] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The prevalence of Listeria spp. on the skin of a hundred fresh chicken carcasses purchased from 20 retail stores in León was investigated using the routine test procedure recommended by the United States Department of Agriculture (USDA). PALCAM and Modified Oxford agar (MOX) were used for isolation. Listeria spp., Listeria monocytogenes, L. innocua, L. welshimeri, L. grayi and L. ivanovii were present in 95%, 32%, 66%, 7%, 4% and 2% of the samples, respectively. Next, an immunoassay test (Listeria Rapid Test; Oxoid, Unipath) and the routine test procedure (USDA) were compared for their ability to detect Listeria spp. on 40 chicken carcasses. When we used MOX for the isolations, the sensitivity of the immunoassay test was 100% and the specificity 85.7%. When we used PALCAM medium the sensitivity and specificity of the test was 94.29% and 80%, respectively.
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Affiliation(s)
- R Capita
- Department of Food Hygiene and Food Technology, Faculty of Veterinary, University of León, Spain.
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12
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Production of mortadella: behavior of Listeria monocytogenes during processing and storage conditions. Meat Sci 2001; 57:13-7. [DOI: 10.1016/s0309-1740(00)00068-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2000] [Revised: 05/24/2000] [Accepted: 05/25/2000] [Indexed: 11/17/2022]
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13
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Manzano M, Cocolin L, Pipan C, Falasca E, Botta GA, Cantoni C, Comi G. Single-strand conformation polymorphism (SSCP) analysis of Listeria monocytogenes iap gene as tool to detect different serogroups. Mol Cell Probes 1997; 11:459-62. [PMID: 9500812 DOI: 10.1006/mcpr.1997.0137] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
PCR-single-strand conformation polymorphism (PCR-SSCP) analysis is a convenient technique for the detection of mutations. As the mobility of single-stranded DNA is sequence-dependent it could therefore be used to determine serotype-related sequence variations in Listeria monocytogenes. Sero-specific patterns were observed in different L. monocytogenes serogroups.
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Affiliation(s)
- M Manzano
- Dipartimento di Scienze degli Alimenti, Facoltà di Agraria, Università di Udine, Italy
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14
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Comi G, Cocolin L, Cantoni C, Manzano M. A RE-PCR method to distinguish Listeria monocytogenes serovars. FEMS IMMUNOLOGY AND MEDICAL MICROBIOLOGY 1997; 18:99-104. [PMID: 9223613 DOI: 10.1111/j.1574-695x.1997.tb01033.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Strains (107) of L. monocytogenes were tested with a PCR-restriction enzyme analysis with two new original primers. A segment of 1395 bp containing the entire iap gene in L. monocytogenes was amplified by the PCR technique. The PCR product was cleaved with the restriction enzymes HindIII and RsaI, and the fragments generated were separated by gel electrophoresis. Two groups of serovars were obtained: one group contained serovars 1/2a and 1/2c, the other group contained serovars 1/2b, 3b and 4b. The PCR-restriction enzyme analysis method described in this paper could be a useful tool for the unambiguous division of L. monocytogenes into two serovar groups, and it could be used to study the evolution of different serotypes and groups of serotypes in foods produced in the same processing plant and processed during the same month. The RE-PCR method used can give a rapid confirm at the subgroup level in the laboratory of an epidemiological association between human disease and suspected sources of contaminated food.
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Affiliation(s)
- G Comi
- Dipartimento di Scienze degli Alimenti, Università degli Studi di Udine, Italy. Food Sci@DSA. Uniud.It
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15
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Sheridan J, Duffy G, McDowell D, Blair I. Development of a surface adhesion immunofluorescent technique for the rapid isolation of Listeria monocytogenes and Listeria innocua from meat. J Appl Microbiol 1997. [DOI: 10.1111/j.1365-2672.1997.tb02855.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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16
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Sheridan JJ, Duffy G, McDowell DA, Blair IS. Development of a surface adhesion immunofluorescent technique for the rapid isolation of Listeria monocytogenes and Listeria innocua from meat. J Appl Microbiol 1997; 82:225-32. [PMID: 12452598 DOI: 10.1111/j.1365-2672.1997.tb03577.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The use of a novel surface adhesion technique to isolate Listeria monocytogenes and Listeria innocua from an enrichment meat system was developed. Minced beef samples inoculated with L. monocytogenes (10 cfu g(-1)) were incubated at 30 degrees C for 14-18 h in a suitable enrichment broth. Listeria monocytogenes cells were isolated from the enriched meat sample by surface adhesion onto a polycarbonate membrane which was attached to a glass microscope slide. The Listeria cells on the membrane were subsequently visualized using an immunofluorescent microscopy procedure. The antibody used in this technique reacts with L. monocytogenes and L. innocua. The technique was demonstrated to have a detection level of log10 3.11 cfu ml(-1). There was excellent correlation (r2 = 0.98) between the counts obtained by this surface adhesion immunofluorescent (SAIF) technique and counts obtained using traditional methods, i.e. plate counts on PALCAM. When the regression equation relating the rapid and standard methods was validated using the data from 50 retail beef mince samples, an rsd value of +/- 0.25 was obtained. No false-negative or false-positive results were recorded for L. monocytogenes or L. innocua species using the SAIF technique.
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Affiliation(s)
- J J Sheridan
- The National Food Centre, Teagasc, Dunsinea, Castleknock, Dublin, Ireland, UK
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17
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Gay M, Cerf O, Davey K. Significance of pre-incubation temperature and inoculum concentration on subsequent growth of Listeria monocytogenes at 14°C. J Appl Microbiol 1996. [DOI: 10.1111/j.1365-2672.1996.tb01937.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Gay M, Cerf O, Davey KR. Significance of pre-incubation temperature and inoculum concentration on subsequent growth of Listeria monocytogenes at 14 degrees C. THE JOURNAL OF APPLIED BACTERIOLOGY 1996; 81:433-8. [PMID: 8896354 DOI: 10.1111/j.1365-2672.1996.tb03530.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The influence of the bacterial concentration of an inoculum (10(1) or 10(3) cfu ml-1) of two strains of Listeria monocytogenes (Scott A: serotype 4b and V7: serotype 1) and one strain of L. innocua (Lin 11), and the time and temperature at which the inoculum was stored (cold storage: 4 degrees C for 4 weeks, or without cold storage: -20 degrees C before immediate transfer), and the temperature at which cells were pre-incubated (30 degrees C and 14 degrees C) on subsequent growth in Richard's broth at 14 degrees C was investigated. Richard's broth at a pH 5.9 was used to simulate potential growth in soft cheese (camembert type) and an incubation temperature of 14 degrees C was used to simulate storage-temperature ripening of cheese. Enumeration of the number of viable cells was by plate count method, except where viable cell numbers were less that 10(3) cfu ml-1, when the MPN (Most Probable Number) technique was used. With cold storage and an inoculum of 10(3) cfu ml-1 (high bacterial concentration) the pre-incubation temperatures (30 degrees C and 14 degrees C) did not significantly influence the subsequent growth curve: there was no significant lag (less that 21 h) and cell numbers peaked in about 8.5 d. However, with cold storage and an inoculum of 10(1) cfu ml-1 (low bacterial concentration) and a pre-incubation temperature of 30 degrees C a significant shift in the growth curve was observed over that pre-incubated at f14 degrees C, with the appearance of a lag of about 7.7 d. At a pre-incubation temperature of 14 degrees C with the low inoculum concentration, there was a measurable lag of about 1 d. Without cold storage and a pre-incubation temperature of 30 degrees C, there was a lag time of 2.3 d. Storage conditions, pre-incubation temperature and inoculum concentration therefore appear to influence the subsequent growth curve. Importantly, however, the growth curves for cultures from inocula, pre-incubated at either 30 degrees C or 14 degrees C, appeared to involve two distinct values of the exponential growth rate (k): the initial portion of the growth curve described by a low value of k and the subsequent portion by a consistently and significantly greater value. The appearance of two distinct growth phases was reproduced in further data determined for all the studied strains of the microorganism. Further study to explain these unexpected and reproducible findings is being conducted.
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Affiliation(s)
- M Gay
- Laboratoire de Génie de l'Hygiène et des Procédés Alimentaires, Institut National de la Recherche Agronomique, Massy, France
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20
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Salvat G, Toquin MT, Michel Y, Colin P. Control of Listeria monocytogenes in the delicatessen industries: the lessons of a listeriosis outbreak in France. Int J Food Microbiol 1995; 25:75-81. [PMID: 7599032 DOI: 10.1016/0168-1605(94)00087-m] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
During a recent outbreak of foodborne listeriosis which occurred in France in 1992, investigations were carried out in order to identify the plants associated with the production of contaminated products. These investigations were made in six 'suspect' delicatessen plants following the first epidemiological investigations, and in one 'control plant'. The first visits were made during working operations. Two hundred and seventy samples were taken ('environmental' swabs, air samples, products), with 68% of the swabs being positive for Listeria monocytogenes in raw product areas, and 33% positives in the finished product area. The epidemic phagovar was identified in a single plant preparing pork tongues in aspic. The major causes of contamination identified were contact of cooked products with soiled surfaces, cross-contamination between 'raw' and 'cooked' channels and the inadequacy of cleaning and disinfection procedures. A second visit was also made to five plants to provide validation of their cleaning and disinfection procedures. Among 112 swabs collected, 17% of the samples from raw product surfaces and 7% from finished product surfaces were found to be positive. These results suggest that cleaning and disinfection procedures were unable to eliminate sources of L. monocytogenes when not correctly applied.
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Affiliation(s)
- G Salvat
- CNEVA/LCRAP/URHQPA, Ploufragan, France
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WHITING RC, MASANA MO. Listeria monocytogenes Survival Model Validated in Simulated Uncooked-Fermented Meat Products for Effects of Nitrite and pH. J Food Sci 1994. [DOI: 10.1111/j.1365-2621.1994.tb08121.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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