1
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Youn HY, Seo KH. Isolation and characterization of halophilic Kocuria
salsicia strains from cheese brine. Food Sci Anim Resour 2022; 42:252-265. [PMID: 35310564 PMCID: PMC8907793 DOI: 10.5851/kosfa.2022.e1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Revised: 01/03/2022] [Accepted: 01/05/2022] [Indexed: 12/02/2022] Open
Abstract
Kocuria salsicia can survive in extreme environments and cause
infections, including catheter-related bacteremia, in humans. Here, we
investigated and evaluated the characteristics of nine K.
salsicia strains (KS1–KS9) isolated from cheese brine from a
farmstead cheese-manufacturing plant in Korea from June to December, 2020.
Staphylococcus aureus American Type Culture Collection
(ATCC) 29213 was used as a positive control in the growth curve analysis and
biofilm-formation assays. All K. salsicia isolates showed
growth at 15% salt concentration and temperatures of 15°C,
25°C, 30°C, 37°C, and 42°C. KS6 and KS8 showed
growth at 5°C, suggesting that they are potential psychrotrophs. In the
biofilm-formation analysis via crystal violet staining, KS6 exhibited the
highest biofilm-forming ability at various temperatures and media [phosphate
buffered saline, nutrient broth (NB), and NB containing 15% sodium
chloride]. At 25°C and 30°C, KS3, KS6, and KS8 showed higher
biofilm-forming ability than S. aureus ATCC 29213. The
antimicrobial resistance of the isolates was evaluated using the
VITEK® 2 system; most isolates were resistant to
marbofloxacin and nitrofurantoin (both 9/9, 100%), followed by
enrofloxacin (7/9, 77.8%). Five of the nine isolates (5/9, 55.6%)
showed multidrug resistance. Our study reports the abilities of K.
salsicia to grow in the presence of high salt concentrations and at
relatively low temperatures, along with its multidrug resistance and tendency to
form biofilms.
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Affiliation(s)
- Hye-Young Youn
- Center for One Health, College of
Veterinary Medicine, Department of Veterinary Public Health, Konkuk
University, Seoul 05029, Korea
| | - Kun-Ho Seo
- Center for One Health, College of
Veterinary Medicine, Department of Veterinary Public Health, Konkuk
University, Seoul 05029, Korea
- Corresponding author: Kun-Ho
Seo, Center for One Health, College of Veterinary Medicine, Department of
Veterinary Public Health, Konkuk University, Seoul 05029, Korea, Tel:
+82-2-450-4121, Fax: +82-2-3436-4128, E-mail:
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2
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Specific detection of the most prevalent five Listeria strains and unspecific detection of 15 Listeria using multiplex real-time PCR. Eur Food Res Technol 2021. [DOI: 10.1007/s00217-021-03697-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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3
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Comparative recovery of Listeria spp. From dairy environmental surfaces using 3M™ and World Bioproducts© environmental swabs with standard enrichment and enumeration methods. Food Control 2020. [DOI: 10.1016/j.foodcont.2020.107272] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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4
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Zoellner C, Ceres K, Ghezzi-Kopel K, Wiedmann M, Ivanek R. Design Elements of Listeria Environmental Monitoring Programs in Food Processing Facilities: A Scoping Review of Research and Guidance Materials. Compr Rev Food Sci Food Saf 2018; 17:1156-1171. [PMID: 33350161 DOI: 10.1111/1541-4337.12366] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Revised: 05/04/2018] [Accepted: 05/11/2018] [Indexed: 01/08/2023]
Abstract
Occurrence of Listeria monocytogenes (Lm), the causative agent of listeriosis, in food processing facilities presents considerable challenges to food producers and food safety authorities. Design of an effective, risk-based environmental monitoring (EM) program is essential for finding and eliminating Lm from the processing environment to prevent product contamination. A scoping review was conducted to collate and synthesize available research and guidance materials on Listeria EM in food processing facilities. An exhaustive search was performed to identify all available research, industry and regulatory documents, and search results were screened for relevance based on eligibility criteria. After screening, 198 references were subjected to an in-depth review and categorized according to objectives for conducting Listeria sampling in food processing facilities and food sector. Mapping of the literature revealed research and guidance gaps by food sector, as fresh produce was the focus in only 10 references, compared to 72 on meat, 52 on fish and seafood, and 50 on dairy. Review of reported practices and guidance highlighted key design elements of EM, including the number, location, timing and frequency of sampling, as well as methods of detection and confirmation, and record-keeping. While utilization of molecular subtyping methods is a trend that will continue to advance understanding of Listeria contamination risks, improved study design and reporting standards by researchers will be essential to assist the food industry optimize their EM design and decision-making. The comprehensive collection of documents identified and synthesized in this review aids continued efforts to minimize the risk of Lm contaminated foods.
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Affiliation(s)
- Claire Zoellner
- Dept. of Population Medicine and Diagnostic Sciences, Cornell Univ., Ithaca, N.Y. 14850, U.S.A
| | - Kristina Ceres
- Dept. of Population Medicine and Diagnostic Sciences, Cornell Univ., Ithaca, N.Y. 14850, U.S.A
| | - Kate Ghezzi-Kopel
- Albert R. Mann Library, Univ. Library, 237 Mann Dr, Ithaca, N.Y. 14853, U.S.A
| | - Martin Wiedmann
- Dept. of Food Science, Cornell Univ., Ithaca, N.Y. 14853, U.S.A
| | - Renata Ivanek
- Dept. of Population Medicine and Diagnostic Sciences, Cornell Univ., Ithaca, N.Y. 14850, U.S.A
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5
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Kang IB, Kim DH, Chon JW, Seo KH. Effect of microbial control measures on farmstead cheesemaking and antimicrobial resistance of Staphylococcus aureus
and Enterococcus
spp. isolates. J Food Saf 2017. [DOI: 10.1111/jfs.12432] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Il-Byeong Kang
- Center for One Health; College of Veterinary Medicine, Konkuk University; Seoul The Republic of Korea
| | - Dong-Hyeon Kim
- Center for One Health; College of Veterinary Medicine, Konkuk University; Seoul The Republic of Korea
| | - Jung-Whan Chon
- Center for One Health; College of Veterinary Medicine, Konkuk University; Seoul The Republic of Korea
| | - Kun-Ho Seo
- Center for One Health; College of Veterinary Medicine, Konkuk University; Seoul The Republic of Korea
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6
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Josephs-Spaulding J, Beeler E, Singh OV. Human microbiome versus food-borne pathogens: friend or foe. Appl Microbiol Biotechnol 2016; 100:4845-63. [PMID: 27102132 DOI: 10.1007/s00253-016-7523-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Revised: 03/30/2016] [Accepted: 04/03/2016] [Indexed: 12/16/2022]
Abstract
As food safety advances, there is a great need to maintain, distribute, and provide high-quality food to a much broader consumer base. There is also an ever-growing "arms race" between pathogens and humans as food manufacturers. The human microbiome is a collective organ of microbes that have found community niches while associating with their host and other microorganisms. Humans play an important role in modifying the environment of these organisms through their life choices, especially through individual diet. The composition of an individual's diet influences the digestive system-an ecosystem with the greatest number and largest diversity of organisms currently known. Organisms living on and within food have the potential to be either friends or foes to the consumer. Maintenance of this system can have multiple benefits, but lack of maintenance can lead to a host of chronic and preventable diseases. Overall, this dynamic system is influenced by intense competition from food-borne pathogens, lifestyle, overall diet, and presiding host-associated microbiota.
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Affiliation(s)
- Jonathan Josephs-Spaulding
- Division of Biological and Health Sciences, University of Pittsburgh, 300 Campus Drive, Bradford, PA, 16701, USA
| | - Erik Beeler
- Division of Biological and Health Sciences, University of Pittsburgh, 300 Campus Drive, Bradford, PA, 16701, USA
| | - Om V Singh
- Division of Biological and Health Sciences, University of Pittsburgh, 300 Campus Drive, Bradford, PA, 16701, USA.
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7
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Gómez D, Iguácel LP, Rota MC, Carramiñana JJ, Ariño A, Yangüela J. Occurrence of Listeria monocytogenes in Ready-to-Eat Meat Products and Meat Processing Plants in Spain. Foods 2015; 4:271-282. [PMID: 28231204 PMCID: PMC5224534 DOI: 10.3390/foods4030271] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 07/06/2015] [Accepted: 07/08/2015] [Indexed: 11/23/2022] Open
Abstract
The aim of this work was to study the occurrence of Listeria monocytogenes in several types of ready-to-eat (RTE) meat products and in the environment of meat processing plants. A total of 129 samples of RTE meat products and 110 samples from work surfaces and equipment were analyzed. L. monocytogenes was detected in 6 out of 35 cooked products (17.14%), 21 out of 57 raw-cured products (36.84%), and 9 out of 37 dry-cured, salted products (24.32%). The number of sample units that exceeded the food safety limit of 100 cfu/g decreased from the manufacture date to half shelf life, and then it was further reduced at the end of shelf life. L. monocytogenes was detected in 25 out of 110 (22.72%) food contact surfaces. The number of positive and negative results from both food and environmental samples were cross-tabulated and the calculated Cohen's kappa coefficient (κ) was 0.3233, indicating a fair agreement in terms of Listeria contamination. L.monocytogenes was recovered after cleaning and disinfection procedures in four plants, highlighting the importance of thorough cleaning and disinfection.
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Affiliation(s)
- Diego Gómez
- Department of Animal Production and Food Science, Veterinary Faculty, University of Zaragoza, c/Miguel Servet 177, Zaragoza 50013, Spain.
| | - Laura Pilar Iguácel
- Agrifood Research and Technology Centre of Aragón (CITA), Avda. Montañana 930, Zaragoza 50059, Spain.
| | - Mª Carmen Rota
- Department of Animal Production and Food Science, Veterinary Faculty, University of Zaragoza, c/Miguel Servet 177, Zaragoza 50013, Spain.
| | - Juan José Carramiñana
- Department of Animal Production and Food Science, Veterinary Faculty, University of Zaragoza, c/Miguel Servet 177, Zaragoza 50013, Spain.
| | - Agustín Ariño
- Department of Animal Production and Food Science, Veterinary Faculty, University of Zaragoza, c/Miguel Servet 177, Zaragoza 50013, Spain.
| | - Javier Yangüela
- Department of Animal Production and Food Science, Veterinary Faculty, University of Zaragoza, c/Miguel Servet 177, Zaragoza 50013, Spain.
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8
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Quantitative detection of Listeria monocytogenes in raw milk and soft cheeses: Culture-independent versus liquid- and solid-based culture-dependent real time PCR approaches. Lebensm Wiss Technol 2014. [DOI: 10.1016/j.lwt.2014.03.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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9
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Cabrita P, Trigo MJ, Ferreira RB, Brito L. Is the exoproteome important for bacterial pathogenesis? Lessons learned from interstrain exoprotein diversity in Listeria monocytogenes grown at different temperatures. OMICS-A JOURNAL OF INTEGRATIVE BIOLOGY 2014; 18:553-69. [PMID: 25127015 DOI: 10.1089/omi.2013.0151] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Bacterial exoproteomes vary in composition and quantity among species and within each species, depending on the environmental conditions to which the cells are exposed. This article critically reviews the literature available on exoproteins synthesized by the foodborne pathogenic bacterium Listeria monocytogenes grown at different temperatures. The main challenges posed for exoproteome analyses and the strategies that are being used to overcome these constraints are discussed. Over thirty exoproteins from L. monocytogenes are considered, and the multifunctionality of some of them is discussed. Thus, at the host temperature of 37°C, good examples are provided by Lmo0443, a potential marker for low virulence, and by the virulence factors internalin C (InlC) and listeriolysin O (LLO). Based on the reported LLO-induced mucin exocytosis, a model is proposed for the involvement of extracellular LLO in optimizing the conditions for InlC intervention in the invasion of intestinal epithelial cells. At lower growth temperatures, exoproteins such as flagellin (FlaA) and oligopeptide permease (OppA) may explain the persistence of particular strains in the food industry environment, eventually allowing the development of new tools to eradicate L. monocytogenes, a major concern for public health.
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Affiliation(s)
- Paula Cabrita
- 1 CBAA/DRAT-Departamento dos Recursos Naturais, Ambiente e Território, Instituto Superior de Agronomia, University of Lisbon , Lisbon, Portugal
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10
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Fusco V, Quero GM. Culture-Dependent and Culture-Independent Nucleic-Acid-Based Methods Used in the Microbial Safety Assessment of Milk and Dairy Products. Compr Rev Food Sci Food Saf 2014; 13:493-537. [DOI: 10.1111/1541-4337.12074] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Accepted: 03/08/2014] [Indexed: 12/12/2022]
Affiliation(s)
- Vincenzina Fusco
- Nal. Research Council of Italy; Inst. of Sciences of Food Production (CNR-ISPA); Bari Italy
| | - Grazia Marina Quero
- Nal. Research Council of Italy; Inst. of Sciences of Food Production (CNR-ISPA); Bari Italy
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11
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Abstract
ABSTRACT
As the manufacture of cheese relies in part on the select outgrowth of microorganisms, such conditions can also allow for the multiplication of unwanted contaminants. Milk ultimately becomes contaminated with microorganisms originating from infection, the farm environment, and feedstuffs, as well as milking and processing equipment. Thus, poor sanitation, improper milk handling, and animal health issues can result in not only decreased yield and poor quality but also sporadic cases and outbreaks of dairy-related disease. The entry, establishment, and persistence of food-borne pathogens in dairy processing environments also present a considerable risk to products postprocessing. Food safety management systems coupled with regulatory policies and microbiological standards for milk and milk products currently implemented in various nations work to reduce risk while improving the quality and safety of cheese and other dairy products. With that, cheese has enjoyed an excellent food safety record with relatively few outbreaks of food-borne disease considering the amount of cheese produced and consumed worldwide. However, as cheese production and consumption continue to grow, we must remain vigilant in ensuring the continued production of safe, high-quality cheese.
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12
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Dalmasso M, Bolocan AS, Hernandez M, Kapetanakou AE, Kuchta T, Manios SG, Melero B, Minarovičová J, Muhterem M, Nicolau AI, Rovira J, Skandamis PN, Stessl B, Wagner M, Jordan K, Rodríguez-Lázaro D. Comparison of polymerase chain reaction methods and plating for analysis of enriched cultures of Listeria monocytogenes when using the ISO11290-1 method. J Microbiol Methods 2013; 98:8-14. [PMID: 24384162 DOI: 10.1016/j.mimet.2013.12.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 12/18/2013] [Accepted: 12/20/2013] [Indexed: 10/25/2022]
Abstract
Analysis for Listeria monocytogenes by ISO11290-1 is time-consuming, entailing two enrichment steps and subsequent plating on agar plates, taking five days without isolate confirmation. The aim of this study was to determine if a polymerase chain reaction (PCR) assay could be used for analysis of the first and second enrichment broths, saving four or two days, respectively. In a comprehensive approach involving six European laboratories, PCR and traditional plating of both enrichment broths from the ISO11290-1 method were compared for the detection of L. monocytogenes in 872 food, raw material and processing environment samples from 13 different dairy and meat food chains. After the first and second enrichments, total DNA was extracted from the enriched cultures and analysed for the presence of L. monocytogenes DNA by PCR. DNA extraction by chaotropic solid-phase extraction (spin column-based silica) combined with real-time PCR (RTi-PCR) was required as it was shown that crude DNA extraction applying sonication lysis and boiling followed by traditional gel-based PCR resulted in fewer positive results than plating. The RTi-PCR results were compared to plating, as defined by the ISO11290-1 method. For first and second enrichments, 90% of the samples gave the same results by RTi-PCR and plating, whatever the RTi-PCR method used. For the samples that gave different results, plating was significantly more accurate for detection of positive samples than RTi-PCR from the first enrichment, but RTi-PCR detected a greater number of positive samples than plating from the second enrichment, regardless of the RTi-PCR method used. RTi-PCR was more accurate for non-food contact surface and food contact surface samples than for food and raw material samples especially from the first enrichment, probably because of sample matrix interference. Even though RTi-PCR analysis of the first enrichment showed less positive results than plating, in outbreak scenarios where a rapid result is required, RTi-PCR could be an efficient way to get a preliminary result to be then confirmed by plating. Using DNA extraction from the second enrichment broth followed by RTi-PCR was reliable and a confirmed result could be obtained in three days, as against seven days by ISO11290-1.
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Affiliation(s)
- Marion Dalmasso
- Teagasc Food Research Centre, Moorepark, Fermoy, Co. Cork, Ireland
| | - Andrei Sorin Bolocan
- Faculty of Food Science and Engineering, Dunarea de Jos University of Galati, Romania
| | | | | | - Tomáš Kuchta
- Food Research Institute, Priemyselná 4, 824 75 Bratislava, Slovakia
| | - Stavros G Manios
- Agricultural University of Athens, Iera odos 75, 118 55 Athens, Greece
| | | | | | - Meryem Muhterem
- Institute for Milk Hygiene, Milk Technology and Food Science, Department of Veterinary Public Health and Food Science, University of Veterinary Medicine, Vienna, Veterinärplatz 1, 1210 Vienna, Austria
| | - Anca Ioana Nicolau
- Faculty of Food Science and Engineering, Dunarea de Jos University of Galati, Romania
| | | | | | - Beatrix Stessl
- Institute for Milk Hygiene, Milk Technology and Food Science, Department of Veterinary Public Health and Food Science, University of Veterinary Medicine, Vienna, Veterinärplatz 1, 1210 Vienna, Austria
| | - Martin Wagner
- Institute for Milk Hygiene, Milk Technology and Food Science, Department of Veterinary Public Health and Food Science, University of Veterinary Medicine, Vienna, Veterinärplatz 1, 1210 Vienna, Austria
| | - Kieran Jordan
- Teagasc Food Research Centre, Moorepark, Fermoy, Co. Cork, Ireland.
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13
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Survival of Listeria monocytogenes Cells and the Effect of Extended Frozen Storage (−20 °C) on the Expression of Its Virulence Gene. Appl Biochem Biotechnol 2013; 170:1174-83. [DOI: 10.1007/s12010-013-0253-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2012] [Accepted: 04/21/2013] [Indexed: 12/27/2022]
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14
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Comparative Analysis of the Exoproteomes ofListeria monocytogenesStrains Grown at Low Temperatures. Foodborne Pathog Dis 2013; 10:428-34. [DOI: 10.1089/fpd.2012.1385] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
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15
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Viswanath P, Murugesan L, Knabel SJ, Verghese B, Chikthimmah N, Laborde LF. Incidence of Listeria monocytogenes and Listeria spp. in a small-scale mushroom production facility. J Food Prot 2013; 76:608-15. [PMID: 23575122 DOI: 10.4315/0362-028x.jfp-12-292] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Listeria monocytogenes is a foodborne pathogen of significant concern to the agricultural and food processing industry because of its ability to grow and persist in cool and moist environments and its association with listeriosis, a disease with a very high mortality rate. Although there have been no listeriosis outbreaks attributed to fresh mushrooms in the United States, retail surveys and recalls are evidence that L. monocytogenes contamination of mushrooms (Agaricus bisporus) can occur. The objective of this study was to determine the prevalence of Listeria spp., including L. monocytogenes, in a small-scale mushroom production facility on the campus of the Pennsylvania State University in the United States. Of 184 samples taken from five production zones within the facility, 29 (15.8%) samples were positive for Listeria spp. Among the Listeria spp. isolates, L. innocua was most prevalent (10.3%) followed by L. welshimeri (3.3%), L. monocytogenes (1.6%), and L. grayi (0.5%). L. monocytogenes was recovered only from the phase I raw material composting area. Isolates of L. monocytogenes were confirmed and serotyped by multiplex PCR. The epidemiological relatedness of the three L. monocytogenes isolates to those serotypes or lineages frequently encountered in listeriosis infections was determined by multi-virulence-locus sequence typing using six virulence genes, namely, prfA, inlB, inlC, dal, clpP, and lisR. The phylogenetic positions of the three isolates in the dendrogram prepared with data from other isolates of L. monocytogenes showed that all isolates were grouped with serotype 4a, lineage IIIA. To date, this serotype has rarely been reported in foodborne disease outbreaks.
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Affiliation(s)
- Prema Viswanath
- Department of Food Science, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
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17
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Listeria monocytogenes in Irish Farmhouse cheese processing environments. Int J Food Microbiol 2011; 145 Suppl 1:S39-45. [DOI: 10.1016/j.ijfoodmicro.2010.10.012] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Revised: 09/28/2010] [Accepted: 10/17/2010] [Indexed: 11/23/2022]
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18
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D'Amico DJ, Donnelly CW. Detection, isolation, and incidence of Listeria spp. in small-scale artisan cheese processing facilities: a methods comparison. J Food Prot 2009; 72:2499-507. [PMID: 20003731 DOI: 10.4315/0362-028x-72.12.2499] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Environmental sampling, focused on environmental sites with a high probability of contamination, was conducted in eight artisan cheese processing facilities. Samples (n = 236) from 86 food contact surfaces and 150 non-food contact surfaces were examined for the presence of Listeria spp. by comparing the efficacy of three different primary enrichment media used in five detection and isolation methods. University of Vermont broth was the most sensitive primary enrichment medium for the detection of Listeria spp., including Listeria monocytogenes. These results, however, did not differ significantly from those obtained with Listeria repair broth or Oxoid 24 Listeria enrichment broth. When full methods were considered, the use of dual enrichment methods identified the most Listeria spp.-positive samples, whereas the BAX System PCR Assay for the Genus Listeria 24E provided the most rapid results (approximately 30 h). Cultural results from the direct plating of secondary enrichment broths were generally in agreement with PCR results when compared within methods. Despite minor differences in efficacy, all five methods were in agreement with one another. Overall, 24 (10.7%) of the 236 environmental samples were positive for Listeria spp., all of which were collected from non-food contact surfaces. Nine of these sites were also positive in previous sampling events, suggesting that these sites serve as Listeria niches and that certain ribotypes are particularly persistent, inhabiting environments and specific sites for over 2 years. Overall, our results suggest that the extent of Listeria spp. contamination, notably L. monocytogenes, in small-scale artisan cheese processing environments is low.
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Affiliation(s)
- Dennis J D'Amico
- Department of Nutrition and Food Sciences, University of Vermont, Burlington, Vermont 05405, USA.
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