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Wang B, Liu S, Sui Z, Wang J, Wang Y, Gu S. Rapid Flow Cytometric Detection of Single Viable Salmonella Cells in Milk Powder. Foodborne Pathog Dis 2020; 17:447-458. [PMID: 32004087 DOI: 10.1089/fpd.2019.2748] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Salmonella, a highly virulent food-borne pathogen transmitted through food, can cause severe infectious diseases in a large number of people through a single outbreak, due to its low infective doses. In this study, a flow cytometry (FCM)-based method was developed for the rapid detection of single viable Salmonella cells with dual staining of fluorescein isothiocyanate (FITC)-labeled anti-Salmonella antibody and propidium iodide (PI) dyes. The FCM-based method includes 6 h of pre-enrichment, 40 min of target cell isolation, and 20 min of dual staining and FCM analysis. The developed method demonstrated high specificity for the detection of 23 Salmonella strains and 22 food-borne pathogenic non-Salmonella strains. Furthermore, the analyses of 30 samples of milk powder artificially contaminated with single Salmonella cells, 123 samples of retail milk powder, and 6 samples of Salmonella-positive milk powder were performed by the FCM-based as well as traditional plate-based methods for testing the efficiency of the methods. The two methods yielded similar results for the detection of pathogens in all milk powder samples. In conclusion, the developed FCM-based method was found to be efficient in detecting single viable Salmonella cells in milk powder within 7 h. The proposed dual-color FITC assay combined with pre-enrichment offers a great potential for the rapid and sensitive detection of other pathogens in dairy products.
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Affiliation(s)
- Bin Wang
- Center for Advanced Measurement Science, National Institute of Metrology, Beijing, China.,Research Center for Ginseng Genetic Resources Development and Utilization, Jilin Agricultural University, Changchun, China
| | - Siyuan Liu
- Center for Advanced Measurement Science, National Institute of Metrology, Beijing, China
| | - Zhiwei Sui
- Center for Advanced Measurement Science, National Institute of Metrology, Beijing, China
| | - Jing Wang
- Center for Advanced Measurement Science, National Institute of Metrology, Beijing, China
| | - Yi Wang
- Research Center for Ginseng Genetic Resources Development and Utilization, Jilin Agricultural University, Changchun, China
| | - Shaopeng Gu
- Shanxi Key Laboratory of Environmental Veterinary Medicine, College of Animal Science and Veterinary Medicine, Shanxi Agricultural University, Taigu, China
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Deng X, Tang S, Wu Q, Tian J, Riley WW, Chen Z. Inactivation of Vibrio parahaemolyticus by antimicrobial photodynamic technology using methylene blue. JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 2016; 96:1601-1608. [PMID: 25989459 DOI: 10.1002/jsfa.7261] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Revised: 03/30/2015] [Accepted: 05/14/2015] [Indexed: 06/04/2023]
Abstract
BACKGROUND Vibrio parahaemolyticus is the leading causative pathogen of gastroenteritis often related to contaminated seafood. Photodynamic inactivation has been recently proposed as a strategy for killing cells and viruses. The objective of this study was to verify the bactericidal effects caused by photodynamic inactivation using methylene blue (MB) over V. parahaemolyticus via flow cytometry, agarose gel electrophoresis and sodium dodecyl sulfate polyacrylamide gel electrophoresis. Vibrio parahaemolyticus counts were determined using the most probable number method. A scanning electron microscope and a transmission electron microscope were employed to intuitively analyze internal and external cell structure. RESULTS Combination of MB and laser treatment significantly inhibited the growth of V. parahaemolyticus. The inactivation rate of V. parahaemolyticus was >99.99% and its counts were reduced by 5 log10 in the presence of 0.05 mg mL(-1) MB when illuminated with visible light (power density 200 mW cm(-2)) for 25 min. All inactivated cells showed morphological changes, leakage of cytoplasm and degradation of protein and DNA. CONCLUSION Results from this study indicated that photodynamic technology using MB produced significant inactivation of V. parahaemolyticus mainly brought about by the degradation of protein and DNA.
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Affiliation(s)
- Xi Deng
- Department of Food Science and Engineering, Jinan University, Guangzhou, 510632, China
| | - Shuze Tang
- Department of Food Science and Engineering, Jinan University, Guangzhou, 510632, China
| | - Qian Wu
- Department of Food Science and Engineering, Jinan University, Guangzhou, 510632, China
| | - Juan Tian
- Department of Food Science, South China Agricultural University, Guangzhou, 510642, China
| | - William W Riley
- Department of Food Science and Engineering, Jinan University, Guangzhou, 510632, China
| | - Zhenqiang Chen
- Department of Photoelectrical Engineering, Jinan University, Guangzhou, 510632, China
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Füchslin HP, Kötzsch S, Keserue HA, Egli T. Rapid and quantitative detection of Legionella pneumophila applying immunomagnetic separation and flow cytometry. Cytometry A 2010; 77:264-74. [PMID: 20099248 DOI: 10.1002/cyto.a.20858] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Legionella is a pathogenic bacterium that establishes and proliferates well in water storage and distribution systems. Worldwide it is responsible for numerous outbreaks of legionellosis, which can be fatal. Despite recent advances in molecular and immunological methods, the official, internationally accepted detection method for Legionella spp. in water samples (ISO 11371) is still based on cultivation. This method has major disadvantages such as a long assay time of 10 days and the detection of cultivable cells only. Therefore, we developed a cultivation-independent, quantitative, and fast detection method for Legionella pneumophila in water samples. It consists of four steps, starting with (1) a concentrating step, in which cells present in one litre of water are concentrated into 5 ml by filtration (pore size 0.45 microm), (2) then cells are resuspended with sterile filtered buffer and double-stained with FITC- and Alexa-conjugated Legionella-specific antibodies, (3) subsequently, the cells are immunomagnetically caught, and (4) finally, fluorescently labeled Legionella cells were flow cytometrically detected and quantified. The efficiency of each step was tested separately. The whole method allows detection of L. pneumophila in 180 min with a detection limit of around 500 cells/l and a recovery of Legionella cells of 52.1 % out of spiked tap water. Fluorescence microscopy and flow cytometric cell-counting correlated well.
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Affiliation(s)
- Hans Peter Füchslin
- Eawag (Swiss Federal Institute for Aquatic Science and Technology), Dübendorf, Switzerland
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Hammes F, Egli T. Cytometric methods for measuring bacteria in water: advantages, pitfalls and applications. Anal Bioanal Chem 2010; 397:1083-95. [DOI: 10.1007/s00216-010-3646-3] [Citation(s) in RCA: 128] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2010] [Revised: 03/05/2010] [Accepted: 03/08/2010] [Indexed: 11/30/2022]
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Cronin UP, Wilkinson MG. Physiological response of Bacillus cereus vegetative cells to simulated food processing treatments. J Food Prot 2008; 71:2168-76. [PMID: 19044257 DOI: 10.4315/0362-028x-71.11.2168] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Vegetative cells of the spore-former Bacillus cereus were exposed to a number of treatments commonly used in commercial food preparation or during equipment cleaning and decontamination. Treated suspensions were then analyzed for reductions (CFU per milliliter) by plate counting and changes in levels of ATP and ADP released from cells with a bioluminescence-based assay. With the use of flow cytometry (FCM), the physiological status of individual cells before and after exposure to treatments was determined by staining of control and treated cells with three pairs of physiological dyes (SYTO 9/propidium iodide, carboxyfluorescein diacetate/Hoechst 33342, and C12-resazurin/SYTOX Green). Good agreement was found between plate counting and FCM. In general, treatments giving rise to the highest count reductions also had the greatest effects on cell membrane permeability (measured with the use of propidium iodide or SYTOX Green), esterase activity (measured with carboxyfluorescein diacetate), or redox activity (C12-resazurin). FCM data demonstrated the extent of heterogeneity of vegetative cell responses to treatments in, for example, the treatment with 5% H2O2, which caused a 6-log reduction in which approximately 95% of the population was composed of membrane-damaged cells (as reflected by their permeability to SYTOX Green), whereas in treatment with 0.09% (wt/vol) potassium sorbate, which caused only a 1-log reduction, not more than 40% of cells were membrane damaged. The approaches described in this work can be applied to gain a greater understanding of bacterial responses to food control measures, generate more accurate inactivation models, or screen novel prospective food control measures.
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Affiliation(s)
- Ultan P Cronin
- Department of Life Sciences, University of Limerick, Castletroy, County Limerick, Ireland
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Arnold JW. Colorimetric assay for biofilms in wet processing conditions. J Ind Microbiol Biotechnol 2008; 35:1475-80. [PMID: 18712536 DOI: 10.1007/s10295-008-0449-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2008] [Accepted: 07/30/2008] [Indexed: 10/21/2022]
Abstract
Controlling bacterial biofilms is necessary for food safety and industrial processing in clean room environments. Our goal was to develop a method to quantitatively measure biofilm produced by pathogens under wet poultry production and processing conditions. Stainless steel and glass coupons were incubated in aqueous media containing reduced nutrients and exposed to Listeria monocytogenes under static temperature and humidity conditions. Samples were measured separately by biofilm assay and viable cell density, and then confirmed by spectrophotometry and microscopy. The biofilm assay resulted in different t groupings from the cell density. The mean from the biofilm assay was 0.50, and the error% was 0.595. The mean of the log10 density (cfu/cm2) was 5.90, and the standard deviation ranged from 0.127 to 0.438 on 24 coupons. The typical sequence of biofilm development, followed by microscopy of biofilm grown on glass coupons, exhibited a change from dispersed single cells to an all-over pattern of clumps with few dispersed cells. L. monocytogenes formed biofilms on all of the substrata tested. Bacterial counts from planktonic cultures at 24, 48, 72, and 144 h confirmed that L. monocytogenes remained viable throughout the experiment and reached equilibrium between 6 and 24 h. The cell density log10/ml was 8.01, 8.03, 7.69, and 6.66, respectively; and the standard deviation ranged from 0.156 to 0.394. The data will be used to grow stable biofilms of Listeria spp. collected from the food processing environment for further study. This is the first use of the crystal violet assay for measurement of bacterial biofilms on stainless steel under these conditions. The methods tested are applicable to other bacteria and substrata.
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Affiliation(s)
- Judy W Arnold
- USDA-ARS, Russell Research Center, 950 College Station Road, Athens, GA 30605, USA.
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Yitzhaki S, Barnea A, Keysary A, Zahavy E. New approach for serological testing for leptospirosis by using detection of leptospira agglutination by flow cytometry light scatter analysis. J Clin Microbiol 2004; 42:1680-5. [PMID: 15071025 PMCID: PMC387560 DOI: 10.1128/jcm.42.4.1680-1685.2004] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Leptospirosis is considered an important reemerging infectious disease worldwide. The standard and most widespread method for the diagnosis of leptospirosis is the microscopic agglutination test (MAT). This test is laborious and time-consuming, and the interpretation of the results is subjective. In the present work we describe an application of flow cytometry (FCM) as a tool for the serological diagnosis of leptospirosis. The analysis is based on the sensitivity of FCM to the size and shape of the bacteria analyzed by measurement of light scatter parameters: forward scatter (FSC) and side scatter (SSC). The addition of positive serum to an infecting leptospiral serovar results in a shift of the light scatter parameter to a different location with higher FSC and SSC values, indicating the formation of leptospiral aggregates. By using immunofluorescent staining, we have shown that the large particles formed are the agglutinated leptospires. Quantification of the agglutination process has been achieved by calculating an agglutination factor (Af), based on changes in the light scatter parameters measured by FCM. Af enables us to determine the specificity of the serological reaction of the patient serum with each leptospiral serovar. In this work, 27 serum samples from 18 leptospirosis patients were tested by both the MAT and the FCM techniques, in which each serum sample was tested against 13 serovars. Twenty-six human serum samples derived from patients with a variety of other defined illnesses were used as negative controls and enabled us to define the Af threshold value as < 9.3 for negative patients, while any value higher than that would be a positive result for leptospirosis. Compared to MAT, the FCM technique was found to be more specific and sensitive, especially in identifying the serogroup in the acute phase of the disease. The whole process was found to be rapid and took less than 1.5 h. Moreover, FCM analysis is objective and can be automated for the handling of large numbers of samples.
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Affiliation(s)
- S Yitzhaki
- Department of Infectious Diseases, Israel Institute for Biological Research, Ness-Ziona 74100, Israel.
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Yamaguchi N, Sasada M, Yamanaka M, Nasu M. Rapid detection of respiring Escherichia coli O157:H7 in apple juice, milk, and ground beef by flow cytometry. Cytometry A 2003; 54:27-35. [PMID: 12820118 DOI: 10.1002/cyto.a.10045] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
BACKGROUND Rapid and simple methods to detect viable pathogenic microbes in foods and drinks are required. Flow cytometry was used for the rapid detection of respiring Escherichia coli O157:H7 cells in apple juice, milk, and ground beef. METHODS CTC (5-cyano-2,3-ditolyl tetrazolium chloride) was used to estimate the respiratory activity of bacteria. Fluorescein isothiocyanate (FITC)-labeled anti-E. coli O157:H7 direct antibody (FA) was used for the specific detection of target cells. Food samples were inoculated with starved E. coli O157:H7 and E. coli K-12 cells, and analyzed by both fluorescent microscopy and flow cytometry after double staining with FA and CTC. RESULTS Respiring E. coli O157:H7 cells in food samples showed strong fluorescence of both FA (green) and CTC (red); thus, they could be clearly and specifically distinguished from respiring E. coli K-12 or inactive cells. A good correlation was achieved in flow cytometric analysis between the numbers of inoculated viable E. coli O157:H7 and those detected in milk and apple juice. The detection threshold for this flow cytometry for E. coli O157:H7 in milk, apple juice, and ground beef was 10(3) cells/ml (milk and apple juice) or 10(3) cells/g (ground beef) of sample when the total bacterial number in the sample was 10(6) cells/ml. CONCLUSIONS Respiring E. coli O157:H7 in food samples can be detected specifically within a few hours. Flow cytometry with FA-CTC double staining can be used to examine food contamination with various pathogenic microbes demonstrating physiologic activity through the use of a suitable fluorescent antibody.
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Affiliation(s)
- Nobuyasu Yamaguchi
- Environmental Science and Microbiology, Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan
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Chitarra LG, Langerak CJ, Bergervoet JHW, van den Bulk RW. Detection of the plant pathogenic bacterium Xanthomonas campestris pv. Campestris in seed extracts of Brassica sp. Applying fluorescent antibodies and flow cytometry. CYTOMETRY 2002; 47:118-26. [PMID: 11813202 DOI: 10.1002/cyto.10058] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND Xanthomonas campestris pv. campestris (Xcc) is a seed-transmitted plant pathogenic bacterium that causes black rot of crucifers. Seed lots and plants are screened for contamination with this pathogen using plating or serological assays. These methods, however, are time consuming and not very sensitive, respectively. Therefore, flow cytometry (FCM) was evaluated as a tool for the rapid detection and quantification of Xcc cells labeled with a mixture of specific fluorescein isothicyanate (FITC)-monoclonal antibodies (mAb) in pure culture, in mixed cultures of Xcc with either the common saprophyte Pseudomonas fluorescens (Psf) or a nonpathogenic X. campestris isolate (Xc), and in crude seed extracts. METHODS The mAb 18G12, conjugated with FITC, was tested at dilutions of 1:50, 1:100, 1:200, and 1:400. For mixed suspensions of Xcc and Psf, mAb 18G12 was used at a dilution of 1:100. The combination of mAbs 18G12, 2F4, and 20H6, all conjugated with FITC, was used at a dilution of 1:100 for the detection and quantification of Xcc cells in mixed suspensions containing Xcc and Xc and in crude seed extracts. The analyses were performed with a Coulter EPICS XL-MCL flow cytometer, at low flow rate during 2 min. RESULTS Using FCM, Xcc cells labeled with FITC-conjugated mAbs (18G12, 2F4, and 20H6) were detected and quantified rapidly at low numbers, i.e., 10(3) colony-forming units per milliliter in pure and in mixed cultures with Psf. The presence of the nonpathogenic Xc in the seed extracts did not interfere with the FCM results. Xcc cells were distinguished from the cells of other organisms and from small particles present in the seed extract based on the high-intensity fluorescence of the labeled cells. CONCLUSION The application of FCM in combination with FITC-conjugated mAbs appears to be a promising technique for the detection and quantification of Xcc cells in seed extracts of crucifers.
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Affiliation(s)
- L G Chitarra
- Business Unit Plant Development and Reproduction, Plant Research International B.V., Wageningen, The Netherlands
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Affiliation(s)
- S A Sincock
- Purdue Cytometry Laboratories, Department of Basic Medical Sciences, Purdue University, West Lafayette, Indiana 47907, USA
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Gunasekera TS, Attfield PV, Veal DA. A flow cytometry method for rapid detection and enumeration of total bacteria in milk. Appl Environ Microbiol 2000; 66:1228-32. [PMID: 10698799 PMCID: PMC91970 DOI: 10.1128/aem.66.3.1228-1232.2000] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Application of flow cytometry (FCM) to microbial analysis of milk is hampered by the presence of milk proteins and lipid particles. Here we report on the development of a rapid (</=1-h) FCM assay based on enzymatic clearing of milk to determine total bacteria in milk. When bacteria were added to ultra-heat-treated milk, a good correlation (r >/= 0.98) between the FCM assay and the more conventional methods of plating and direct microscopic counting was achieved. Raw milk data showed a significant correlation (P < 0.01) and a good agreement (r = 0.91) between FCM and standard plate count methods. The detection limit of the FCM assay was </=10(4) bacteria ml of milk(-1). This limit is below the level of detection required to satisfy legislation in many countries and states.
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Affiliation(s)
- T S Gunasekera
- Centre for Fluorimetric Applications in Biotechnology, Department of Biological Sciences, Macquarie University, Sydney, New South Wales 2109, Australia.
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Kusunoki H, Hu D, Piyankarage RH, Sugii S, Uemura T. Flow cytometric analysis for enterotoxin exposed on Clostridium perfringens spores. J Vet Med Sci 1998; 60:1357-9. [PMID: 9879540 DOI: 10.1292/jvms.60.1357] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Flow cytometric method (FCM) with fluorescent-labeled anti-CPE antibody was applied to develop a rapid, specific, and convenient method to detect enterotoxin (CPE) exposed on the surface of spores of Clostridium perfringens. The results obtained indicate that FCM can specifically detect CPE exposed on C. perfringens spores for a short time. Thus, FCM is found to be a rapid, specific, and convenient assay method for detection of CPE exposed on C. perfringens spores, suggesting that it will be hopefully useful to diagnose food poisoning caused by C. perfringens.
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Affiliation(s)
- H Kusunoki
- Department of Veterinary Science, College of Agriculture, Osaka Prefecture University, Japan
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Ueckert J, Breeuwer P, Abee T, Stephens P, von Caron GN, ter Steeg PF. Flow cytometry applications in physiological study and detection of foodborne microorganisms. Int J Food Microbiol 1995; 28:317-26. [PMID: 8750676 DOI: 10.1016/0168-1605(95)00066-6] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- J Ueckert
- Unilever Research Laboratorium, Vlaardingen, The Netherlands
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McClelland RG, Pinder AC. Detection of low levels of specific Salmonella species by fluorescent antibodies and flow cytometry. THE JOURNAL OF APPLIED BACTERIOLOGY 1994; 77:440-7. [PMID: 7989272 DOI: 10.1111/j.1365-2672.1994.tb03447.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The use of fluorescently-labelled monoclonal antibodies, with detection by multi-parameter flow cytometry, was investigated for the rapid detection of salmonellas in pure cultures. Accurate detection of specific Salmonella serotypes was demonstrated down to levels of below 10(4) cells ml-1 (within 30 min) and 1 cell ml-1 (after 6 h non-selective pre-enrichment). This level of sensitivity was attained even in the presence of high levels of other bacterial species that would otherwise have interfered with the results. With combinations of different antibodies, each with a unique fluorescent label, simultaneous analysis for two species was possible.
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Affiliation(s)
- R G McClelland
- Department of Food Biophysics, AFRC Institute of Food Research, Norwich Laboratory, UK
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