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Microbial Risk Assessment of Industrial Ice Cream Marketed in Italy. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12041988] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Ice cream is a frozen dairy dessert consumed worldwide. The frozen state may give a positive impression regarding microbiological safety; however, transmission of foodborne pathogens can also occur through ice cream consumption. A total of 200 samples of milk-based industrial ice cream, with and without inclusions, were purchased at different mass-market retailers in Italy and analyzed for the detection and enumeration of the aerobic colonies, Enterobacteriaceae, coagulase-positive staphylococci, Salmonella spp. and Listeria monocytogenes. Results were classified according to different ranges of acceptability, whose limits were set for each microbiological parameter. Unsatisfactory loads were obtained for two and nine samples as regarded the aerobic colonies and Enterobacteriaceae, respectively. L. monocytogenes was detected in 16 samples, and in three of them, the loads exceeded the legal limit of acceptability (≤100 cfu/g) during marketing. No unsatisfactory loads were obtained for coagulase-positive staphylococci and no Salmonella spp. was detected. The results obtained allow speculation that inclusions may be a relevant source of contamination for industrial ice cream. However, inadequate manufacturing and hygiene practices also threaten the safety of the finished product. Ice cream is a complex food matrix, and a comprehensive approach to the whole production system is required to ensure high standards of quality and safety.
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Ranta J, Mikkelä A, Suomi J, Tuominen P. BIKE: Dietary Exposure Model for Foodborne Microbiological and Chemical Hazards. Foods 2021; 10:2520. [PMID: 34828801 PMCID: PMC8621415 DOI: 10.3390/foods10112520] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 09/22/2021] [Accepted: 09/24/2021] [Indexed: 11/20/2022] Open
Abstract
BIKE is a Bayesian dietary exposure assessment model for microbiological and chemical hazards. A graphical user interface was developed for running the model and inspecting the results. It is based on connected Bayesian hierarchical models, utilizing OpenBUGS and R in tandem. According to occurrence and consumption data given as inputs, a specific BUGS code is automatically written for running the Bayesian model in the background. The user interface is based on shiny app. Chronic and acute exposures are estimated for chemical and microbiological hazards, respectively. Uncertainty and variability in exposures are visualized, and a few optional model structures can be used. Simulated synthetic data are provided with BIKE for an example, resembling real occurrence and consumption data. BIKE is open source and available from github.
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Affiliation(s)
- Jukka Ranta
- Risk Assessment Unit, Finnish Food Authority, 00790 Helsinki, Finland; (A.M.); (J.S.); (P.T.)
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Ku S, Ximenes E, Kreke T, Foster K, Couetil JL, Zuponcic J, Zhao X, Hoagland L, Deering AJ, Ladisch MR. Microbial enrichment and multiplexed microfiltration for accelerated detection of Salmonella in spinach. Biotechnol Prog 2019; 35:e2874. [PMID: 31228331 DOI: 10.1002/btpr.2874] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 06/11/2019] [Accepted: 06/17/2019] [Indexed: 01/01/2023]
Abstract
To attain Salmonella detection thresholds in spinach suspensions using enrichment media requires at least 24 hr. Separation and concentration of selected microorganisms via microfiltration and microfugation reduce time for sample preparation, especially when working with large volumes of vegetable suspensions. This facilitates accelerated detection of Salmonella in spinach suspensions, and may contribute to effectively monitoring this pathogen before it reaches the consumer. We report a microfiltration-based protocol for accelerated sample preparation to concentrate and recover ≤1 colony forming unit (CFU) Salmonella/g pathogen-free spinach. Store-bought samples of spinach and a spinach plant subjected to two environmental conditions (temperature and light exposure) during its production were tested. The overall procedure involves extraction with buffer, a short enrichment step, prefiltration using a nylon filter, crossflow hollow fiber microfiltration, and retentate centrifugation to bring microbial cells to detection levels. Based on 1 CFU Salmonella/g frozen spinach, and a Poisson distribution statistical analyses with 99% probability, we calculated that 3 hr of incubation, when followed by microfiltration, is sufficient to reach the 2 log concentration required for Salmonella detection within 7 hr. Longer enrichment times (5 hr or more) is needed for concentrations lower than 1 CFU Salmonella/g of ready to eat spinach. The recovered microbial cells were identified and confirmed as Salmonella using both polymerase chain reaction (PCR) and plating methods. Different environmental conditions tested during production did not affect Salmonella viability; this demonstrated the broad adaptability of Salmonella and emphasized the need for methods that enable efficient monitoring of production for the presence of this pathogen.
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Affiliation(s)
- Seockmo Ku
- Laboratory of Renewable Resources Engineering, Purdue University, West Lafayette, Indiana
| | - Eduardo Ximenes
- Laboratory of Renewable Resources Engineering, Purdue University, West Lafayette, Indiana.,Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, Indiana
| | - Thomas Kreke
- Laboratory of Renewable Resources Engineering, Purdue University, West Lafayette, Indiana
| | - Kirk Foster
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana
| | - Justin L Couetil
- Laboratory of Renewable Resources Engineering, Purdue University, West Lafayette, Indiana
| | - Jessica Zuponcic
- Laboratory of Renewable Resources Engineering, Purdue University, West Lafayette, Indiana.,Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, Indiana
| | - Xiaojun Zhao
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana
| | - Lori Hoagland
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana
| | - Amanda J Deering
- Department of Food Science, Purdue University, West Lafayette, Indiana
| | - Michael R Ladisch
- Laboratory of Renewable Resources Engineering, Purdue University, West Lafayette, Indiana.,Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, Indiana.,Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana
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Ku S, Ximenes E, Kreke T, Foster K, Deering AJ, Ladisch MR. Microfiltration of enzyme treated egg whites for accelerated detection of viable
Salmonella. Biotechnol Prog 2016; 32:1464-1471. [DOI: 10.1002/btpr.2343] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 08/04/2016] [Indexed: 11/08/2022]
Affiliation(s)
- Seockmo Ku
- Laboratory of Renewable Resources EngineeringPurdue UniversityWest Lafayette IN47907
- Dept. of Agricultural and Biological EngineeringPurdue UniversityWest Lafayette IN47907
| | - Eduardo Ximenes
- Laboratory of Renewable Resources EngineeringPurdue UniversityWest Lafayette IN47907
- Dept. of Agricultural and Biological EngineeringPurdue UniversityWest Lafayette IN47907
| | - Thomas Kreke
- Laboratory of Renewable Resources EngineeringPurdue UniversityWest Lafayette IN47907
| | - Kirk Foster
- Weldon School of Biomedical EngineeringPurdue UniversityWest Lafayette IN47907
| | | | - Michael R. Ladisch
- Laboratory of Renewable Resources EngineeringPurdue UniversityWest Lafayette IN47907
- Dept. of Agricultural and Biological EngineeringPurdue UniversityWest Lafayette IN47907
- Weldon School of Biomedical EngineeringPurdue UniversityWest Lafayette IN47907
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Enumeration of salmonellae in table eggs, pasteurized egg products, and egg-containing dishes by using quantitative real-time PCR. Appl Environ Microbiol 2013; 80:1616-22. [PMID: 24362433 DOI: 10.1128/aem.03360-13] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Salmonellae are a major cause of food-borne outbreaks in Europe, with eggs and egg products being identified as major sources. Due to the low levels of salmonellae in eggs and egg products, direct quantification is difficult. In the present study, enrichment quantitative real-time PCR (qPCR) was employed for enumeration of salmonellae in different matrices: table eggs, pasteurized egg products, and egg-containing dishes. Salmonella enterica serovar Enteritidis and S. enterica serovar Tennessee were used to artificially contaminate these matrices. The results showed a linear regression between the numbers of salmonellae and the quantification cycle (Cq) values for all matrices used, with the exception of pasteurized egg white. Standard curves were constructed by using both stationary-phase cells and heat-stressed cells, with similar results. Finally, this method was used to evaluate the fate of salmonellae in two egg-containing dishes, long egg and tiramisu, at abused refrigeration temperatures, and results indicated the growth of bacteria over a 1-week period. In conclusion, enrichment qPCR was shown to be reliable for enumeration of salmonellae in different egg products.
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Waturangi DE, Wennars M, Suhartono MX, Wijaya YF. Edible ice in Jakarta, Indonesia, is contaminated with multidrug-resistant Vibrio cholerae with virulence potential. J Med Microbiol 2013; 62:352-359. [DOI: 10.1099/jmm.0.048769-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Diana E. Waturangi
- Faculty of Biotechnology, Atma Jaya Catholic University of Indonesia, Jakarta, Indonesia
| | - Melissa Wennars
- Faculty of Biotechnology, Atma Jaya Catholic University of Indonesia, Jakarta, Indonesia
| | - Magda X. Suhartono
- Faculty of Biotechnology, Atma Jaya Catholic University of Indonesia, Jakarta, Indonesia
| | - Yenata F. Wijaya
- Faculty of Biotechnology, Atma Jaya Catholic University of Indonesia, Jakarta, Indonesia
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8
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Cheung PY, Kam KM. Salmonella in food surveillance: PCR, immunoassays, and other rapid detection and quantification methods. Food Res Int 2012. [DOI: 10.1016/j.foodres.2011.12.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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9
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The challenge of merging food safety diagnostic needs with quantitative PCR platforms. Trends Food Sci Technol 2011. [DOI: 10.1016/j.tifs.2011.02.009] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Shashidhar R, Srivastava I, Bandekar JR. Quantification of Salmonella in Food Samples from India Using the MINI-MSRV MPN and Modified MINI-MSRV MPN Methods. J Food Sci 2011; 76:M564-7. [DOI: 10.1111/j.1750-3841.2011.02366.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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11
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Krämer N, Löfström C, Vigre H, Hoorfar J, Bunge C, Malorny B. A novel strategy to obtain quantitative data for modelling: Combined enrichment and real-time PCR for enumeration of salmonellae from pig carcasses. Int J Food Microbiol 2011; 145 Suppl 1:S86-95. [DOI: 10.1016/j.ijfoodmicro.2010.08.026] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2010] [Revised: 08/26/2010] [Accepted: 08/27/2010] [Indexed: 10/19/2022]
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12
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Zhao X, Wang L, Chu J, Li Y, Li Y, Xu Z, Li L, Shirtliff ME, He X, Liu Y, Wang J, Yang L. Development and application of a rapid and simple loop-mediated isothermal amplification method for food-borne Salmonella detection. Food Sci Biotechnol 2010. [DOI: 10.1007/s10068-010-0234-4] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Dwivedi HP, Jaykus LA. Detection of pathogens in foods: the current state-of-the-art and future directions. Crit Rev Microbiol 2010; 37:40-63. [PMID: 20925593 DOI: 10.3109/1040841x.2010.506430] [Citation(s) in RCA: 179] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Over the last fifty years, microbiologists have developed reliable culture-based techniques to detect food borne pathogens. Although these are considered to be the "gold-standard," they remain cumbersome and time consuming. Despite the advent of rapid detection methods such as ELISA and PCR, it is clear that reduction and/or elimination of cultural enrichment will be essential in the quest for truly real-time detection methods. As such, there is an important role for bacterial concentration and purification from the sample matrix as a step preceding detection, so-called pre-analytical sample processing. This article reviews recent advancements in food borne pathogen detection and discusses future methods with a focus on pre-analytical sample processing, culture independent methods, and biosensors.
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Affiliation(s)
- Hari P Dwivedi
- Department of Food, Bioprocessing and Nutrition Sciences, North Carolina State University, Raleigh, NC-27695-7624, USA.
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Jyoti A, Ram S, Vajpayee P, Singh G, Dwivedi PD, Jain SK, Shanker R. Contamination of surface and potable water in South Asia by Salmonellae: culture-independent quantification with molecular beacon real-time PCR. THE SCIENCE OF THE TOTAL ENVIRONMENT 2010; 408:1256-1263. [PMID: 20035972 DOI: 10.1016/j.scitotenv.2009.11.056] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2009] [Revised: 11/18/2009] [Accepted: 11/25/2009] [Indexed: 05/28/2023]
Abstract
Low numbers (15-100CFU) of Salmonella in food or water may pose a public health risk. The management of infections caused by Salmonella spp. during outbreaks or forecasting of contamination of aquatic resources largely depends on rapid, sensitive and accurate diagnostic in few hours. In this study, a real-time PCR assay in Molecular-Beacon format was developed and culture-independent quantitative enumeration of Salmonella spp. in surface and potable water is being reported for the first time from northern part of India. Molecular Beacon was designed in highly conserved region of invA gene (present in wide range of Salmonella serotypes including all subspecies) encoding an essential component of the invasion associated specialized type Ø protein secretion apparatus for detection of Salmonella spp. in water. The assay could detect directly 10 and 1 genomic equivalent of Salmonella typhimurium ATCC 14028 per PCR with detection probability of 100 and 20%, respectively. Further, the assay could detect 10CFU/PCR or more of reference strain (S. typhimurium ATCC 14028) without any enrichment in the presence of 10(8)CFUml(-1) of non-pathogenic E. coli (E. coli DH5alpha) with 100% detection probability. The assay could enumerate Salmonella spp. in surface (n=40) and potable waters (n=10) directly (without enrichment). Results indicate that northern India is at high risk of developing Salmonella borne infections. Further, real-time PCR assay in Molecular Beacon format can be used for identification of critical contamination points in natural water resources and potable water distribution systems, necessary to implement vaccination plan timely for prevention of waterborne outbreaks caused by Salmonella spp.
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Affiliation(s)
- Anurag Jyoti
- Environmental Microbiology, Indian Institute of Toxicology Research (C.S.I.R.), Lucknow, U.P., India
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15
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Levin RE. The Use of Molecular Methods for Detecting and DiscriminatingSalmonellaAssociated with Foods — A Review. FOOD BIOTECHNOL 2009. [DOI: 10.1080/08905430903320982] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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16
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Lee SH, Jung BY, Rayamahji N, Lee HS, Jeon WJ, Choi KS, Kweon CH, Yoo HS. A multiplex real-time PCR for differential detection and quantification of Salmonella spp., Salmonella enterica serovar Typhimurium and Enteritidis in meats. J Vet Sci 2009; 10:43-51. [PMID: 19255523 PMCID: PMC2801102 DOI: 10.4142/jvs.2009.10.1.43] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Salmonella (S.) Typhimurium and S. Enteritidis are the major causative agents of food-borne illnesses worldwide. Currently, a rapid detection system using multiplex real-time polymerase chain reaction (PCR) has been applied for other food-borne pathogens such as Escherichia coli, Staphylococcus aureus and Streptococcus spp. A multiplex real-time PCR was developed for the simultaneous detection of Salmonella spp., especially S. Typhimurium and S. Enteritidis, in beef and pork. For the specific and sensitive multiplex real-time PCR, three representative primers and probes were designed based on sequence data from Genbank. Among the three DNA extraction methods (boiling, alkaline lysis, and QIAamp DNA Mini Kit), the QIAamp DNA Mini Kit was the most sensitive in this study. The optimized multiplex real-time PCR was applied to artificially inoculated beef or pork. The detection sensitivity of the multiplex real-time PCR was increased. The specificity of the multiplex real-time PCR assay, using 128 pure-cultured bacteria including 110 Salmonella isolates and 18 non-Salmonella isolates, was 100%, 100% and 99.1% for Salmonella spp., S. Typhimurium and S. Enteritidis, respectively. The sensitivity was 100%, 100% and 91.7% for Salmonella spp., S. Typhimurium and S. Enteritidis, respectively. The multiplex real-time PCR assay developed in this study could detect up to 0.54 ± 0.09 and 0.65 ± 0.07 log10 CFU/ml for S. Typhimurium and S. Enteritidis for beef, 1.45 ± 0.21 and 1.65 ± 0.07 log10 CFU/ml for S. Typhimurium and S. Enteritidis for pork, respectively, with all conditions optimized. Our results indicated that the multiplex real-time PCR assay developed in this study could sensitively detect Salmonella spp. and specifically differentiate S. Typhimurium from S. Enteritidis in meats.
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Affiliation(s)
- Su Hwa Lee
- National Veterinary Research and Quarantine Service, Anyang 430-824, Korea
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Lu Y, Yang W, Shi L, Li L, Alam MJ, Guo S, Miyoshi SI. Specific Detection of Viable Salmonella Cells by an Ethidium Monoazide-Loop Mediated Isothermal Amplification (EMA-LAMP) Method. ACTA ACUST UNITED AC 2009. [DOI: 10.1248/jhs.55.820] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Yuxia Lu
- College of Light Industry and Food Sciences, South China University of Technology
| | - Weiqing Yang
- Department of Clinical Microbiology, Guangdong Medical College
| | - Lei Shi
- College of Light Industry and Food Sciences, South China University of Technology
| | - Lin Li
- College of Light Industry and Food Sciences, South China University of Technology
| | | | - Siyuan Guo
- College of Light Industry and Food Sciences, South China University of Technology
| | - Shin-ichi Miyoshi
- Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University
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Cheung PY, Kwok KK, Kam KM. Application of BAX system, Tecra Unique Salmonella test, and a conventional culture method for the detection of Salmonella in ready-to-eat and raw foods. J Appl Microbiol 2008; 103:219-27. [PMID: 17584468 DOI: 10.1111/j.1365-2672.2006.03210.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
AIMS To compare the BAX system, the Tecra Unique Salmonella test, and a conventional culture method for the detection of Salmonella in various foods. METHODS AND RESULTS Ready-to-eat and raw foods were inoculated with Salmonella serotype Typhimurium, Salmonella serotype Enteritidis, Salmonella serotype Typhi, or Salmonella serotype Derby. Incubated pre-enrichment cultures were examined using the BAX system, the Tecra Unique Salmonella test, and a conventional culture method. Salmonella could be detected in all ready-to-eat food samples inoculated with S. Typhimurium, S. Enteritidis, or S. Derby, with any of the three test methods. However, false negatives were obtained with the Tecra test and the culture method when samples with higher background flora were inoculated with S. Typhi. Sensitivity test results suggested the two rapid tests performed as well as the culture method in the detection of 10(1) CFU of S. Typhimurium in 25-g cooked or raw food. CONCLUSIONS The BAX system and the Tecra Unique Salmonella test demonstrated results comparable with those of the culture method in the detection of Salmonella serotypes used except S. Typhi. SIGNIFICANCE AND IMPACT OF THE STUDY This is the first evaluation of the BAX system, the Tecra Unique Salmonella test, and a culture method in the detection of Salmonella in a variety of western and oriental foods.
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Affiliation(s)
- P-Y Cheung
- Food and Water Laboratory, Public Health Laboratory Services Branch, Department of Health, Hong Kong.
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Wang L, Shi L, Alam M, Geng Y, Li L. Specific and rapid detection of foodborne Salmonella by loop-mediated isothermal amplification method. Food Res Int 2008. [DOI: 10.1016/j.foodres.2007.09.005] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Enumeration of salmonella bacteria in food and feed samples by real-time PCR for quantitative microbial risk assessment. Appl Environ Microbiol 2007; 74:1299-304. [PMID: 18165357 DOI: 10.1128/aem.02489-07] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Hong J, Jung WK, Kim JM, Kim SH, Koo HC, Ser J, Park YH. Quantification and differentiation of Campylobacter jejuni and Campylobacter coli in raw chicken meats using a real-time PCR method. J Food Prot 2007; 70:2015-22. [PMID: 17900077 DOI: 10.4315/0362-028x-70.9.2015] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Campylobacter species are one of the most common causes of bacterial diarrhea in humans worldwide. The consumption of foods contaminated with two Campylobacter species, C. jejuni and C. coli, is usually associated with most of the infections in humans. In this study, a rapid, reliable, and sensitive multiplex real-time quantitative PCR was developed for the simultaneous detection, identification, and quantification of C. jejuni and C. coli. In addition, the developed method was applied to the 50 samples of raw chicken meat collected from retail stores in Korea. C. jejuni and C. coli were detected in 88 and 86% of the samples by real-time quantitative PCR and the conventional microbiological method, respectively. The specificity of the primer and probe sets was confirmed with 30 C. jejuni, 20 C. coli, and 35 strains of other microbial species. C. jejuni and C. coli could be detected with high specificity in less than 4 h, with a detection limit of 1 log CFU/ml by the developed real-time PCR. The average counts (log CFU per milliliter) of C. jejuni or C. coli obtained by the conventional methods and by the real-time PCR assay were statistically correlated with a correlation coefficient (R2) between 0.73 and 0.78. The real-time PCR assay developed in this study is useful for screening for the presence and simultaneous differential quantification of C. jejuni and C. coli.
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Affiliation(s)
- Joonbae Hong
- Department of Microbiology, College of Veterinary Medicine and BK21 Program for Veterinary Science, Seoul National University, Sillim-dong, Gwanak-gu, Seoul 151-742, Korea
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De Martinis ECP, Duvall RE, Hitchins AD. Real-time PCR detection of 16S rRNA genes speeds most-probable-number enumeration of foodborne Listeria monocytogenes. J Food Prot 2007; 70:1650-5. [PMID: 17685338 DOI: 10.4315/0362-028x-70.7.1650] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Quantifying foodborne pathogens at concentrations of 0.1 to 1,000 CFU/g of food generally involves most-probable-number (MPN) enumeration, which takes at least 4 days. A real-time PCR assay (RTi-PCR) was developed to accelerate MPN enumeration of foodborne Listeria monocytogenes. Foods were spiked from 70 to 110 CFU/g, and triplicate subportions from 0.0001 to 1 g were selectively enriched for 48 h at 30 degrees C. For standard MPN enumeration, the enrichments were subcultured on Oxford agar (48 h at 35 degrees C) to isolate Listeria. For RTi-PCR MPN, the L. monocytogenes cells from the same enrichments were washed and resuspended in 2 ml of sterile water. DNA was extracted by boiling for 10 min. The DNA in the extract's supernatant was targeted with published oligonucleotide primers for amplifying an Lmo-specific sequence of 16S rRNA genes. Amplification was continuously monitored with SYBR Green. The resulting amplicon was characterized by its melting temperature. The L. monocytogenes specificity of the primers was confirmed by testing L. monocytogenes (15 strains), Listeria innocua (11 strains), and Listeria welshimeri, Listeria seeligeri, Listeria ivanovii, and Listeria grayi (1 strain each). Quantitatively spiked milk, lettuce, smoked salmon, Brie cheese, ice cream, pork pâté, salami, ready-to-eat shrimp, raw ground beef, and fresh soft cheese were enumerated by both the standard and the PCR MPN method. The paired results from the two MPN methods agreed well, except for the fresh cheese. For some foods, l-g samples required a decimal dilution for a positive test result, suggesting concentration-dependent food ingredient interference with the RTi-PCR. This RTi-PCR method reduced the time necessary for the MPN enumeration of foodborne L. monocytogenes from 4 to 2 days.
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Affiliation(s)
- Elaine Cristina Pereira De Martinis
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av. do Café s/n, Monte Alegre, 14040-903 Ribeirão Preto, SP, Brazil
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Rodríguez-Lázaro D, Lombard B, Smith H, Rzezutka A, D'Agostino M, Helmuth R, Schroeter A, Malorny B, Miko A, Guerra B, Davison J, Kobilinsky A, Hernández M, Bertheau Y, Cook N. Trends in analytical methodology in food safety and quality: monitoring microorganisms and genetically modified organisms. Trends Food Sci Technol 2007. [DOI: 10.1016/j.tifs.2007.01.009] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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