51
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Bukh AS, Roslev P. Characterization and validation of a chemiluminescent assay based on a 1,2-dioxetane for rapid detection of enterococci in contaminated water and comparison with standard methods and qPCR. J Appl Microbiol 2011; 111:407-16. [PMID: 21575110 DOI: 10.1111/j.1365-2672.2011.05051.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIMS To evaluate the potential for using a novel chemiluminescence-based enzyme assay for rapid detection of enterococci in water contaminated with faecal waste. METHODS AND RESULTS The novel assay (EntLight) was based on the enzymatic hydrolysis of the chemiluminescent 1,2-dioxetane [(4-methoxy-4(3-β-d-glucoside-4-chlorophenyl)]spiro[1,2-dioxetane-3-1,3-tricyclo[7·3·1·0(2,7) ]tridec-2,7-ene] specific for β-d-glucosidase. The specificity of the proposed EntLight assay was characterized using 26 different Enterococcus strains and 10 bacterial genera other than Enterococcus. With an analysis time of ≤8 h, the assay was found to be sensitive and specific. Validation experiments were carried out using water samples contaminated with raw municipal wastewater in comparison with qPCR and ISO standard methods. EntLight was successfully applied to detect enterococci in contaminated water within ≤8 h, and the proposed assay correlated well with both qPCR and ISO standard methods (R(2) > 0·776). CONCLUSIONS EntLight can be applied to rapid and simple detection of viable enterococci in water contaminated with faecal matter. SIGNIFICANCE AND IMPACT OF THE STUDY The novel EntLight assay and qPCR have the potential to be used as methods for early warning (1-7 h) of faecal pollutions in different water types.
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Affiliation(s)
- A S Bukh
- Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Aalborg, Denmark
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Wang Y, Tian JC, Yan Q. Advances in development of biochemical culture media for identification of intestinal bacteria. Shijie Huaren Xiaohua Zazhi 2011; 19:1165-1168. [DOI: 10.11569/wcjd.v19.i11.1165] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Recently, great advances have been made in bacterial classification and identification; however, bacterial classification and identification still greatly depend on biochemical reactions in clinical setting. Identification of bacteria with all-in-one multi-use chromogenic media represents a new approach. It is easy to handle, has a high specificity, can improve the application of bacterial identification in clinical setting, and represents a promising tendency for bacterial identification.
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Sezgintürk MK, Dinçkaya E. A biosensor for the determination of β-galactosidase activity: a different viewpoint on biosensors. ARTIFICIAL CELLS, BLOOD SUBSTITUTES, AND IMMOBILIZATION BIOTECHNOLOGY 2011; 39:281-8. [PMID: 21351849 DOI: 10.3109/10731199.2011.560119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
β-galactosidase splits lactose into glucose and galactose. Because of its biotechnological interest, we presented a biosensor system in order to monitor β-galactosidase activity. Immobilization steps of the biosensor were identified by cyclic voltammograms and electrochemical impedance spectroscopy. β-galactosidase was voltammetrically detected at about +150 mV (vs. Ag/AgCl) in citrate buffer solution (0.05 M, pH 4.8). The linear response for β-galactosidase detection was in the range of 0.0118 U mL(-1)to 0.47 U mL(-1)and a shorter response time of ∼50 s. Our results demonstrated the biosensor's electrochemical properties and analytical characteristics were very useful and effective for monitoring of β-galactosidase activity.
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54
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Sezgintürk MK, Dinçkaya E. β-galactosidase determination by an electrochemical biosensor mediated with ferrocene. ARTIFICIAL CELLS, BLOOD SUBSTITUTES, AND IMMOBILIZATION BIOTECHNOLOGY 2011; 39:267-73. [PMID: 21338333 DOI: 10.3109/10731199.2011.559644] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Abstract: In this paper, a new viewpoint on the activity determination of β-galactosidase is reported. Glucose oxidase was directly immobilized on a glassy carbon electrode and mediated by ferrocene. The biosensor's performance was based on mediated electron transfer by ferrocene, which reduced via glucose oxidase reaction. In this reaction, substrate of glucose oxidase, glucose was provided by the activity of β-galactosidase in the sample. The parameters of the fabrication process for the electrode were optimized. Experimental conditions influencing the biosensor performance, such as pH, ferrocene and lactose concentrations, and temperature, were investigated and assessed. Finally, the biosensor was successfully applied to determination of β-galactosidase activity of artificial intestinal juice.
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55
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Rapid and simple biochemical detection for Salmonella spp. using modified LB broth and the MUCAP test. Food Sci Biotechnol 2011. [DOI: 10.1007/s10068-011-0027-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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Jasson V, Jacxsens L, Luning P, Rajkovic A, Uyttendaele M. Alternative microbial methods: An overview and selection criteria. Food Microbiol 2010; 27:710-30. [DOI: 10.1016/j.fm.2010.04.008] [Citation(s) in RCA: 193] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2009] [Revised: 04/12/2010] [Accepted: 04/20/2010] [Indexed: 11/25/2022]
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Samarajeewa A, Glasauer S, Dunfield K. Evaluation of Petrifilm™ EC method for enumeration ofE. colifrom soil. Lett Appl Microbiol 2010; 50:457-61. [DOI: 10.1111/j.1472-765x.2010.02819.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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58
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Fricker CR, Warden PS, Eldred BJ. Understanding the cause of false negative beta-D-glucuronidase reactions in culture media containing fermentable carbohydrate. Lett Appl Microbiol 2010; 50:547-51. [PMID: 20374452 DOI: 10.1111/j.1472-765x.2010.02834.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIMS To explain the basis for false negative beta-glucuronidase reactions seen with culture media containing lactose as a carbon and energy source. METHODS AND RESULTS Escherichia coli strains were assessed for their reactions in culture media containing a beta-d-glucuronidase substrate either with or without lactose. An assay was developed to test for the expression of beta-D-glucuronidase at pH 5.0 and pH 7.2. Strains of E. coli that gave false negative glucuronidase reactions on media containing lactose generally expressed lower concentrations of the enzyme beta-D-glucuronidase than strains that gave positive results, although the difference was by no means consistent. Most strains that were negative on lactose-containing media expressed virtually no beta-D-glucuronidase activity at pH 5.0. Examination of colonies on Membrane lactose glucuronide agar (MLGA) from lightly polluted water showed that c. 10% of the E. coli present failed to yield green colonies on MLGA. CONCLUSIONS E. coli that failed to produce green colonies on MLGA produced lower levels of beta-D-glucuronidase than did strains that formed green colonies, the difference being greater at pH 5.0 than pH 7.2. The false negative rate for E. coli 10% which is similar to that experienced in the study that originally described MLGA. SIGNIFICANCE AND IMPACT OF THE STUDY Strains of E. coli that fail to produce typical colonies on MLGA might produce lower concentrations of the enzyme beta-D-glucuronidase. Whilst the enzyme activity is sufficient to be detected at pH 7.2, fermentation of lactose significantly lowers the pH of the medium and can result in reduced enzyme activity and therefore lack of detection. The false negative rate of c. 10% would be difficult to detect in routine laboratories as it would represent 1% or less of yellow colonies being identified as E. coli (assuming E. coli accounts for 10% of the total coliform population in drinking water).
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Affiliation(s)
- C R Fricker
- Analytical Services Inc., Williston, VT, USA.
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59
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Servais P, Prats J, Passerat J, Garcia-Armisen T. Abundance of culturable versus viable Escherichia coli in freshwater. Can J Microbiol 2009; 55:905-9. [PMID: 19767865 DOI: 10.1139/w09-043] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Approved methods traditionally used for Escherichia coli enumeration in waters are culture-based. However, these methods can underestimate the E. coli abundance in aquatic systems because they do not take into account cells that remain viable but have lost the ability to grow in or on culture media. We investigated, in freshwater samples, the abundance of (i) culturable E. coli, enumerated by the most probable number microplate method and (ii) viable E. coli, estimated using a procedure called DVC-FISH, which couples fluorescent in situ hybridization (FISH) and a viability testing technique (direct viable count (DVC)). The ratio of culturable to viable E. coli was close to 1 in highly contaminated waters (samples with a high concentration of culturable E. coli), but decreased drastically for weakly contaminated samples. This indicates a large fraction of viable but nonculturable (VBNC) E. coli in the latter samples. Microcosm experiments showed that some environmental factors, such as nutrient scarcity and solar irradiation, could lead to the presence of a high proportion of VBNC E. coli.
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Affiliation(s)
- Pierre Servais
- Ecologie des Systémes Aquatiques, Université Libre de Bruxelles, Campus de Plaine, CP 221, Boulevard du Triomphe, B-1050 Bruxelles, Belgium.
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60
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Browne NK, Huang Z, Dockrell M, Hashmi P, Price RG. Evaluation of new chromogenic substrates for the detection of coliforms. J Appl Microbiol 2009; 108:1828-38. [PMID: 19878523 DOI: 10.1111/j.1365-2672.2009.04588.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIMS To evaluate a new range of chromogenic substrates for the detection of beta-galactosidase activity in coliforms and to compare their performance in agar media and broths. METHODS AND RESULTS Sixteen novel galactoside substrates were prepared and incorporated into agar and broth. Their performance was compared using Escherichia coli (five strains), Salmonella (two strains), Enterobacter (two strains), Klebsiella, Pseudomonas, Listeria, Serratia, Shigella, Citrobacter, Proteus and Staphylococcus as well as pathological urine samples. The six substrates out of the initial 16 that showed the greatest sensitivity were VQE-gal, VQM-gal, VLPr-gal, VLE-gal, VLM-gal and VBzTM-gal, whose released chromophores were red, brown or purple. VQE-gal and VLPr-gal were studied in greater detail and were incorporated into agar medium. Coliform colonies appeared red and brown respectively, following incubation at 37 degrees C for 24 h; however, positive results were obtained within a working day. The VQE-gal medium was compared with some commercially available media. CONCLUSIONS The range of substrates described can be used in broths as well as in agars. The VQE agar allows the detection of coliforms within a working day. VQE-gal medium proved to be more sensitive when compared to other available chromogenic media and allows the unambiguous detection of coliforms.
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Affiliation(s)
- N K Browne
- Research & Development, PPR Diagnostics Ltd., London, UK
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61
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Alakomi HL, Saarela M. Salmonellaimportance and current status of detection and surveillance methods. QUALITY ASSURANCE AND SAFETY OF CROPS & FOODS 2009. [DOI: 10.1111/j.1757-837x.2009.00032.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Orenga S, James AL, Manafi M, Perry JD, Pincus DH. Enzymatic substrates in microbiology. J Microbiol Methods 2009; 79:139-55. [PMID: 19679151 DOI: 10.1016/j.mimet.2009.08.001] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2009] [Revised: 07/24/2009] [Accepted: 08/03/2009] [Indexed: 11/15/2022]
Abstract
Enzymatic substrates are powerful tools in biochemistry. They are widely used in microbiology to study metabolic pathways, to monitor metabolism and to detect, enumerate and identify microorganisms. Synthetic enzymatic substrates have been customized for various microbial assays, to detect an expanding range of both new enzymatic activities and target microorganisms. Recent developments in synthetic enzymatic substrates with new spectral, chemical and biochemical properties allow improved detection, enumeration and identification of food-borne microorganisms, clinical pathogens and multi-resistant bacteria in various sample types. In the past 20 years, the range of synthetic enzymatic substrates used in microbiology has been markedly extended supporting the development of new multi-test systems (e.g., Microscan, Vitek 2, Phoenix) and chromogenic culture media. The use of such substrates enables an improvement in time to detection and specificity over conventional tests that employ natural substrates. In the era of intense developments in molecular biology, phenotypic tests involving enzymatic substrates remain useful to analyse both simple and complex samples. Such tests are applicable to diagnostic and research laboratories all over the world.
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Affiliation(s)
- Sylvain Orenga
- Research & Development Microbiology, bioMérieux, 3 route de Port Michaud, La Balme-les-Grottes, France.
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63
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Carrique-Mas JJ, Barnes S, McLaren I, Davies R. Comparison of three plating media for the isolation of Salmonella from poultry environmental samples in Great Britain using ISO 6579:2002 (Annex D). J Appl Microbiol 2009; 107:1976-83. [PMID: 19558470 DOI: 10.1111/j.1365-2672.2009.04386.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
AIMS To evaluate the performance of three Salmonella plating media (Rambach, Xylose Lysine Deoxycholate agar and modified Brilliant Green Agar plus Novobiocin) as part of the ISO 6579: 2002 (Annex D) on poultry environmental samples. METHODS AND RESULTS The samples analysed were those for the European Union Salmonella baseline surveys of laying (N = 3087), broiler (N = 1550), turkey fattening (N = 1540) and turkey breeding (N = 580) flocks for Great Britain. Results were considered separately for Rambach (including and excluding pale orange colonies) and for growth on selective media [Modified semi-solid Rappaport Vassiliadis (MSRV)] after 24 and 48 h of incubation. Overall, Rambach was the most sensitive medium, provided that pale orange colonies were checked. In all cases, an increase in the sensitivity of detection was obtained by plating growth on MSRV after 48 h of incubation. In broilers and laying flocks, the specificity significantly improved when Rambach only was used. CONCLUSION The use of Rambach results in considerable savings compared with the two-plate method prescribed by ISO 6579:2002 (Annex D) without compromising sensitivity. SIGNIFICANCE AND IMPACT OF THE STUDY Salmonella isolation protocols should be reviewed in terms of their efficiency and cost.
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Affiliation(s)
- J J Carrique-Mas
- Department of Food and Environmental Safety, Veterinary Laboratories Agency (VLA) Weybridge, New Haw, Addlestone, Surrey, UK.
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64
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GARRY EILEEN, OUATTARA GRACE, WILLIAMS PATRICK, PESTA MEREDITH. ENUMERATING CHROMOGENIC AGAR PLATES USING THE COLOR QCOUNT AUTOMATED COLONY COUNTER. ACTA ACUST UNITED AC 2009. [DOI: 10.1111/j.1745-4581.2008.00150.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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65
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McLain JET, Williams CF. Seasonal variation in accurate identification of Escherichia coli within a constructed wetland receiving tertiary-treated municipal effluent. WATER RESEARCH 2008; 42:4041-4048. [PMID: 18674793 DOI: 10.1016/j.watres.2008.06.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2008] [Revised: 05/02/2008] [Accepted: 06/03/2008] [Indexed: 05/26/2023]
Abstract
As the reuse of municipal wastewater escalates worldwide as a means to extend increasingly limited water supplies, accurate monitoring of water quality parameters, including Escherichia coli (E. coli), increases in importance. Chromogenic media are often used for detection of E. coli in environmental samples, but the presence of unique levels of organic and inorganic compounds alters reclaimed water chemistry, potentially hindering E. coli detection using enzyme-based chromogenic technology. Over seven months, we monitored E. coli levels using m-Coli Blue 24 broth in a constructed wetland filled with tertiary-treated municipal effluent. No E. coli were isolated in the wetland source waters, but E. coli, total coliforms, and heterotrophic bacteria increased dramatically within the wetland on all sampling dates, most probably due to fecal inputs from resident wildlife populations. Confirmatory testing of isolates presumptive for E. coli revealed a 41% rate of false-positive identification using m-Coli Blue 24 broth over seven months. Seasonal differences were evident, as false-positive rates averaged 35% in summer, but rose sharply to 75% in the late fall and winter. Corrected E. coli levels were significantly correlated with electrical conductivity, indicating that water chemistry may be controlling bacterial survival within the wetland. This is the first study to report that accuracy of chromogenic media for microbial enumeration in reclaimed water may show strong seasonal differences, and highlights the importance of validation of microbiological results from chromogenic media for accurate analysis of reclaimed water quality.
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Affiliation(s)
- Jean E T McLain
- USDA-ARS, US Arid Land Agricultural Research Center, 21881 N Cardon Lane, Maricopa, AZ 85238, USA.
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66
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Sezgintürk MK, Dinçkaya E. β-Galactosidase monitoring by a biosensor based on Clark electrode: Its optimization, characterization and application. Biosens Bioelectron 2008; 23:1799-804. [DOI: 10.1016/j.bios.2008.02.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2007] [Revised: 02/18/2008] [Accepted: 02/21/2008] [Indexed: 10/22/2022]
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67
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Fricker M, Reissbrodt R, Ehling-Schulz M. Evaluation of standard and new chromogenic selective plating media for isolation and identification of Bacillus cereus. Int J Food Microbiol 2008; 121:27-34. [DOI: 10.1016/j.ijfoodmicro.2007.10.012] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2007] [Revised: 08/02/2007] [Accepted: 10/24/2007] [Indexed: 11/26/2022]
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68
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Anderson RJ, Groundwater PW, Huang Y, James AL, Orenga S, Rigby A, Roger-Dalbert C, Perry JD. Synthesis and evaluation of novel chromogenic peptidase substrates based on 9-(4′-aminophenyl)-10-methylacridinium salts as diagnostic tools in clinical bacteriology. Bioorg Med Chem Lett 2008; 18:832-5. [DOI: 10.1016/j.bmcl.2007.11.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2007] [Revised: 11/05/2007] [Accepted: 11/08/2007] [Indexed: 11/29/2022]
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69
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Prats J, Garcia-Armisen T, Larrea J, Servais P. Comparison of culture-based methods to enumerate Escherichia coli in tropical and temperate freshwaters. Lett Appl Microbiol 2007; 46:243-8. [DOI: 10.1111/j.1472-765x.2007.02292.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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70
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Garcia-Armisen T, Prats J, Servais P. Comparison of culturable fecal coliforms and Escherichia coli enumeration in freshwaters. Can J Microbiol 2007; 53:798-801. [PMID: 17668040 DOI: 10.1139/w07-033] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Fecal coliforms (FC) counts were compared with Escherichia coli counts in differently contaminated freshwater samples (n = 166). FC were enumerated by plate count on triphenyl 2,3,5-tetrazolium chloride Tergitol medium. Escherichia coli were enumerated by the most probable number microplate method based on the detection of glucuronidase activity. FC and E. coli counts were highly correlated; an average E. coli/FC ratio equal to 0.77 was found, meaning that on average, 77% of FC were E. coli. Knowing the E. coli/FC ratio allows us to convert the historical microbiological quality data expressed in FC counts into E. coli abundance and thus to compare with present and future monitoring data that are (or will be) based on E. coli enumeration.
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Affiliation(s)
- Tamara Garcia-Armisen
- Ecologie des Systèmes Aquatiques, Université Libre de Bruxelles, Campus de la Plaine, C.P. 221, Boulevard du Triomphe, B-1050 Bruxelles, Belgium
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71
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A novel biosensor for the detection and monitoring of β-d-galactosidase of faecal origin in water. Enzyme Microb Technol 2007. [DOI: 10.1016/j.enzmictec.2006.10.039] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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72
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Pitkänen T, Paakkari P, Miettinen IT, Heinonen-Tanski H, Paulin L, Hänninen ML. Comparison of media for enumeration of coliform bacteria and Escherichia coli in non-disinfected water. J Microbiol Methods 2007; 68:522-9. [PMID: 17150268 DOI: 10.1016/j.mimet.2006.10.007] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2006] [Revised: 10/12/2006] [Accepted: 10/25/2006] [Indexed: 11/21/2022]
Abstract
In this work alternative media for detection and enumeration of E. coli and coliform bacteria were compared to the reference method ISO 9308-1 (LTTC) using non-disinfected water samples with background flora. The alternative media included LES Endo agar medium (LES Endo), Colilert-18 with 51-well Quanti-tray (Colilert), Chromocult Coliform agar (CC), Harlequin E. coli/Coliform medium (HECM) and Chromogenic Escherichia coli/Coliform medium (CECM). A total of 110 samples of groundwater, bathing water and spiked water was used. Our results revealed that confirmation of coliform bacteria counts is necessary, not only on lactose-based LTTC and LES Endo media, but also on the chromogenic agar media tested, due to the growth of oxidase positive colonies. LTTC and CC media also allowed the growth of some morphologically typical coliform colonies containing gram-positive bacteria. The recovery of coliform bacteria was lower on LES Endo than on LTTC. In most cases Colilert, CC, HECM and CECM gave higher coliform counts than LTTC. The use of the LTTC medium led to higher E. coli counts than obtained with any of the alternative mediums. There are three explanations for this: (1) high sensitivity of LTTC, (2) false positives on LTTC or (3) false negatives especially with Colilert, but also with chromogenic agar media. Although LTTC was found to be a very sensitive medium, the high degree of background growth of non-disinfected waters disturbed substantially the use of it. In conclusion, our results suggest that Colilert, CC and CECM are potential alternative media for detection of coliform bacteria and E. coli from non-disinfected water.
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Affiliation(s)
- Tarja Pitkänen
- Laboratory of Environmental Microbiology, National Public Health Institute, P. O. Box 95, FI-70701, Kuopio, Finland.
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73
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James AL, Perry JD, Rigby A, Stanforth SP. Synthesis and evaluation of novel chromogenic aminopeptidase substrates for microorganism detection and identification. Bioorg Med Chem Lett 2007; 17:1418-21. [PMID: 17189689 DOI: 10.1016/j.bmcl.2006.11.088] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2006] [Revised: 11/23/2006] [Accepted: 11/30/2006] [Indexed: 10/23/2022]
Abstract
The amides 8a-e and 10a-c were prepared as chromogenic aminopeptidase substrates. A range of microorganisms were grown in the presence of these compounds and coloured colonies were produced in several cases after addition of acetic acid-thus giving potential methods for the detection of aminopeptidase activity and for microorganism identification.
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Affiliation(s)
- Arthur L James
- School of Applied Sciences, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK
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74
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Rodríguez-Domínguez JC, Balbuzano-Deus A, López-López MA, Rodríguez-Domínguez JC, Kirsch G. An improved synthesis of 1-acetyl-1H-indol-3-yl acetates. J Heterocycl Chem 2007. [DOI: 10.1002/jhet.5570440146] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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75
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Echeverry A, Loneragan GH, Brashears MM. Survival of Escherichia coli O157:H7 in bovine feces over time under various temperature conditions. J Food Prot 2006; 69:2851-5. [PMID: 17186649 DOI: 10.4315/0362-028x-69.12.2851] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Although Escherichia coli O157:H7 prevalence estimates in cattle have increased over time due to improvements in detection methods, fecal sample transport conditions from farm to microbiological laboratories for further analysis may be a factor for prevalence underestimation. The objective of this study was to compare and determine the survival characteristics of E. coli O157:H7 in bovine feces under various storage conditions that could be encountered during transport. Fecal pats were inoculated with a four-strain cocktail of antibiotic-resistant E. coli O157:H7 to contain approximately 1 x 10(5) CFU/g. Inoculated and control samples were taken after 0, 24, 48, 120, and 168 h at each storage temperature and examined for presence and numbers of E. coli O157:H7. Each sample was subdivided and placed at each of the four following temperatures: 37, 23, 4.4 degrees C, and in a plastic cooler with refrigerant packs (0, 4, 4, 21, and 23 degrees C at five sampling times, respectively) to simulate transportation conditions. A statistically significant decrease in the population of the pathogen was observed after 48 h in samples held at 37 degrees C (P < 0.01) and after 168 h at 4.4 degrees C (P = 0.02). At 37 degrees C, E. coli O157:H7 was not detected after 48 h, either by direct plating (P < 0.01) or by immunomagnetic separation. Overall, the results of this study showed that E. coli O157:H7 survived without significant detriment in bovine fecal material inside the cooler for up to 168 h. These results indicate that shipment and storage under these conditions before microbiological analysis would be acceptable and should not affect pathogen detection.
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Affiliation(s)
- A Echeverry
- Department of Animal and Food Sciences, Texas Tech University, Box 42141, Lubbock, Texas 79409, USA
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Lin CM, Zhang L, Doyle MP, Swaminathan B. Comparison of media and sampling locations for isolation of Listeria monocytogenes in queso fresco cheese. J Food Prot 2006; 69:2151-6. [PMID: 16995517 DOI: 10.4315/0362-028x-69.9.2151] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Listeriosis associated with Hispanic-style soft cheese is an ongoing public health concern. Although rapid detection methods based on molecular and immunological technologies have been applied successfully for detecting Listeria monocytogenes in foods, obtaining isolates of the pathogen is a critical procedure for epidemiologic studies and regulatory analysis. Oxford agar, a medium recommended by the U.S. Food and Drug Administration Bacteriological Analytical Manual (BAM) to isolate L. monocytogenes from cheese, is unable to differentiate L. monocytogenes from other Listeria species. Hence, two selective isolation media, L. monocytogenes blood agar (LMBA) and Rapid 'L. mono agar (RLMA), were compared with Oxford agar for isolating L. monocytogenes from cheese. Queso fresco cheese was inoculated at 10(0) or 10(1) CFU/g with a five-strain mixture of L. monocytogenes or with the five-strain L. monocytogenes mixture and Listeria innocua. Cheese samples were stored at 21, 12, and 4 degrees C and Listeria counts were determined at 3, 7, and 10 days; 7, 10, 14, 21 days; and 2, 4, 8, and 12 weeks postinoculation, respectively. Surface and interior cheese samples as well as liquid exudate produced during storage were assayed individually to determine differences in Listeria contamination at different sampling locations. L. monocytogenes was more easily differentiated from L. innocua on RLMA than LMBA and Oxford agar. Similar L. monocytogenes counts (ca. 10(4) CFU/g) were obtained on the last sampling day on the surface and interior of cheese samples (P > 0.05) for all storage temperatures and both initial inoculation levels, but smaller cell numbers were detected in the exudate produced during storage. In addition, simultaneous inoculation of L. innocua with L. monocytogenes did not affect the final L. monocytogenes counts in the cheese. The amount of exudate released from the cheese and decrease of pH correlated with storage temperature. More exudate was produced and a greater decrease of pH occurred at 21 degrees C than at 12 or 4 degrees C. Our results indicate that RLMA is a suitable medium for isolating L. monocytogenes from queso fresco cheese. Higher counts of L. monocytogenes were obtained from surface and interior samples of cheese than from the exudate of the cheese during storage. In addition, pH may be a useful indicator of improperly stored queso fresco cheese.
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Affiliation(s)
- Chia-Min Lin
- Center for Food Safety, University of Georgia, 1109 Experiment Street, Griffin, Georgia 30223-1797, USA
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77
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Mill A, Schlacher T, Katouli M. Tidal and longitudinal variation of faecal indicator bacteria in an estuarine creek in south-east Queensland, Australia. MARINE POLLUTION BULLETIN 2006; 52:881-91. [PMID: 16406429 DOI: 10.1016/j.marpolbul.2005.11.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
A two-part study conducted in Elimbah Creek, a shallow estuarine waterway in south-east Queensland, Australia, examined the variations in physico-chemical parameters of water quality, chlorophyll a, and faecal indicator bacteria abundances of total coliform, Escherichia coli and enterococci, spatially at high and low tide and also over a 12h tidal cycle. Gradients of increasing faecal indicator bacteria from the mouth to the upper, tidal freshwater reaches were observed, despite isolated peaks during either tidal phase. Phytoplankton biomass (measured as chlorophyll a) did not noticeably increase during the study. Variations in the abundances of all three faecal indicator bacteria and their correlations with physico-chemical parameters indicated that although the creek was likely subject to some level of faecal contamination, tidal movement serves to limit faecal indicator and phytoplankton levels in the creek through physico-chemical stress and dilution. However, each faecal indicator bacteria investigated provided different estimations of faecal contamination, which challenges the effectiveness of employing a single type of faecal indicator bacteria when investigating the level of faecal contamination in waterways.
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Affiliation(s)
- A Mill
- Faculty of Science, Health and Education, University of the Sunshine Coast, Maroochydore DC, Qld 4558, Australia
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78
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Yáñez MA, Valor C, Catalán V. A simple and cost-effective method for the quantification of total coliforms and Escherichia coli in potable water. J Microbiol Methods 2006; 65:608-11. [PMID: 16202463 DOI: 10.1016/j.mimet.2005.09.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2005] [Revised: 09/05/2005] [Accepted: 09/08/2005] [Indexed: 11/18/2022]
Abstract
In this study, a new simple and cost-effective method for the study of total coliforms and Escherichia coli in potable water, combining the use of lactose TTC agar and TBX agar, was developed and compared with methods using Chromocult agar and coli ID. The statistical analysis showed no significant difference and a good correlation (R(2)) between the three methods.
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Affiliation(s)
- M A Yáñez
- LABAQUA, SA, Pol. Ind. Las Atalayas, Alicante, Spain
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79
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Maciorowski KG, Herrera P, Jones FT, Pillai SD, Ricke SC. Cultural and Immunological Detection Methods for Salmonella spp. in Animal Feeds - A Review. Vet Res Commun 2006; 30:127-37. [PMID: 16400599 DOI: 10.1007/s11259-006-3221-8] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/22/2004] [Indexed: 11/30/2022]
Abstract
Food-borne salmonellosis continues to be a major public health concern, and contamination with Salmonella spp. in pre-harvest animal production is considered a primary contributor to this problem. Animal feeds can easily become contaminated during primary production, feed mixing and processing as well as during feeding. Consequently, monitoring and surveillance of feeds and feed ingredients for Salmonella spp. contamination may be useful or necessary in the prevention and control of this organism. Cultural and immunological detection methods for salmonellae have been used or suggested as possible approaches for use in animal feeds. Cultural methods remain advantageous owing to their ability to detect viable bacterial cells, while immunological methods have the capability of detecting nonculturable bacterial cells. Advancements and improvements in both methodologies offer opportunities for eventual routine use of these detection technologies in animal feed assays.
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Affiliation(s)
- K G Maciorowski
- Poultry Science Department, Texas A&M University, College Station, TX 77843-2472, USA
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80
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Hamilton WP, Kim M, Thackston EL. Comparison of commercially available Escherichia coli enumeration tests: implications for attaining water quality standards. WATER RESEARCH 2005; 39:4869-78. [PMID: 16313941 DOI: 10.1016/j.watres.2005.02.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2003] [Revised: 12/17/2004] [Accepted: 02/02/2005] [Indexed: 05/05/2023]
Abstract
Many states are replacing microbiological water quality standards based on "fecal" or thermotolerant coliforms (ThCs) with new standards that employ Escherichia coli as the indicator organism. Implicit in these new standards are assumptions about the equivalence of E. coli enumeration tests and the E. coli levels that will provide protection equivalent to former ThC standards. To investigate these assumptions, E. coli levels in split samples (tests conducted on portions of the same grab sample) collected from small urban streams were determined using enzyme-specific media (Colilert, m-ColiBlue24, and nutrient agar with MUG) and compared to levels determined with conventional culture media (m-FC and m-TEC). Although levels observed with all tests were highly correlated, significantly fewer E. coli were enumerated with m-TEC than with enzyme-specific media (paired Student's t-test, alpha>99%). In addition, E. coli were found to comprise a larger fraction (84-104%, depending on the test) of the total presumptive ThC concentration than that suggested by the United States Environmental Protection Agency (63%). Both of these observations (1) the improvement in E. coli yields observed with enzyme-specific media, and (2) the greater proportion of ThC organisms that are E. coli, indicate that more water quality violations will occur when enzyme-specific media are used for testing than if conventional culture media are used.
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Affiliation(s)
- William P Hamilton
- Department of Civil and Environmental Engineering, Vanderbilt University, 400 24th Avenue South, VU Station B 351831, 2301 Vanderbilt Place, Nashville, TN 37235, USA.
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81
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Helander A, Dahl H. Urinary tract infection: a risk factor for false-negative urinary ethyl glucuronide but not ethyl sulfate in the detection of recent alcohol consumption. Clin Chem 2005; 51:1728-30. [PMID: 16120954 DOI: 10.1373/clinchem.2005.051565] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Anders Helander
- Department of Clinical Neuroscience, Karolinska Institutet and University Hospital, Stockholm, Sweden.
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82
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Rostagno MH, Hurd HS, McKean JD. Resting pigs on transport trailers as an intervention strategy to reduce Salmonella enterica prevalence at slaughter. J Food Prot 2005; 68:1720-3. [PMID: 21132985 DOI: 10.4315/0362-028x-68.8.1720] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Recent research has shown that much preharvest Salmonella enterica infection in pigs occurs immediately before slaughter during this rest period in the contaminated abattoir holding pens. The objective of this study was to evaluate a potential intervention strategy to reduce the prevalence of S. enterica-positive pigs at slaughter, which consisted of resting pigs prior to slaughter on their transport vehicle, instead of in the abattoir holding pen. Additionally, the effect of transportation of pigs from farm to the abattoir on S. enterica prevalence was investigated. A total of 120 animals were included in the experiment, divided in four replicates (n = 30 pigs per replicate). Fecal samples were collected from each animal at the farm and at the abattoir, where 15 randomly chosen pigs were unloaded and moved to a holding pen, while the remaining 15 pigs stayed in the transport trailer. After approximately 1.5 h of resting, both groups were slaughtered. Samples collected included distal ileum portion, cecal contents, and ileocecal lymph node. The overall S. enterica prevalence (pigs positive in at least one of the samples collected at slaughter) was higher for pigs held in the abattoir pens (40.7% versus 13.3%, P < 0.05). There was no difference (P > 0.05) for the S. enterica prevalence before and after transportation from farm to abattoir (5.8% versus 0.8%, respectively). This study demonstrates that resting pigs on the transport vehicle has the potential to decrease S. enterica levels entering the abattoir.
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Affiliation(s)
- Marcos H Rostagno
- U.S. Department of Agriculture, Agricultural Research Service, National Animal Disease Center, Preharvest Food Safety and Enteric Diseases Unit, P.O. Box 70, Ames, Iowa 50010, USA
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83
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Miranda JM, Franco CM, Vázquez BI, Fente CA, Barros-Velázquez J, Cepeda A. Evaluation of ChromocultR enterococci agar for the isolation and selective enumeration of Enterococcus spp. in broilers. Lett Appl Microbiol 2005; 41:153-6. [PMID: 16033513 DOI: 10.1111/j.1472-765x.2005.01728.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIMS To investigate the productivity and specificity of a new chromogenic enterococci selective medium (Chromocult enterococci agar) recently developed by Merck. METHODS AND RESULTS The study was carried out comparing Chromocult enterococci agar with MRS agar (Merck), a basal lactic acid bacteria medium in current use. A total of 216 faecal samples from poultry were collected and enterococci populations were counted. Likewise, 100 randomly selected strains were identified for each medium. The differences found between the two media were analysed and discussed. CONCLUSIONS A good sensitivity of 98% was obtained for Chromocult agar and all false-positive isolates obtained were identified as Leuconostoc spp. However significant differences (P<0.01) were obtained between the enterococci species isolation rates identified from these two media, suggesting the poor growth of some species in Chromocult enterococci agar. Viable counts of Enterococcus spp. obtained with MRS agar were significantly higher than those obtained with Chromocult enterococci agar. SIGNIFICANCE AND IMPACT OF THE STUDY The use of chromogenic media for microbiological analysis is increasing. Independent studies are important to evaluate newly developed chromogenic media.
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Affiliation(s)
- J M Miranda
- Laboratorio de Higiene Inspección y Control de Alimentos, Dpto de Química Analítica, Nutrición y Bromatología, Facultad de Veterinaria, Universidad de Santiago de Compostela, Lugo, Spain
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84
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Lebaron P, Henry A, Lepeuple AS, Pena G, Servais P. An operational method for the real-time monitoring of E. coli numbers in bathing waters. MARINE POLLUTION BULLETIN 2005; 50:652-9. [PMID: 15935180 DOI: 10.1016/j.marpolbul.2005.01.016] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The aim of this study was to investigate the potential application of the beta-d-glucuronidase (GLUase) activity measurement for the routine detection and quantification of E. coli in marine bathing waters. GLUase activity was measured as the rate of hydrolysis of 4-methylumbelliferyl-beta-d-glucuronide. Culturable E. coli were quantified by the most probable number (MPN) microplate method. Both methods were applied to a large set of seawater samples. Significant correlation was found between the log of GLUase activity and the log of culturable E. coli. The mean coefficient of variation (CV) of the GLUase activity was less than 15% at concentrations around the current standards of International regulations whereas the CV of the microplate method was around 30%. When samples were stored at 4 degrees C and 20 degrees C, the mean CV of the GLUase activity remained below 15% up to 6 hours after sample collection whereas the range of variation of the microplate method varied between 10 and 50%. We concluded that the GLUase activity is an operational, reproducible, simple, very rapid and low cost method for the real-time enumeration of E. coli in bathing waters and should be preferred to the microplate method. The GLUase activity method should be routinely applied to the rapid enumeration of E. coli in recreational waters and recommendations for its application were suggested to water quality managers.
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Affiliation(s)
- Philippe Lebaron
- Observatoire Océanologique, Université Pierre et Marie Curie, CNRS-INSU UMR 7621, Banyuls-sur-mer, France.
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85
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Mellado V, Yáñez MA, Catalán V. Evaluation of the MicroFoss system for the analysis of Escherichia coli in water. Microbiol Res 2005; 161:20-4. [PMID: 16338586 DOI: 10.1016/j.micres.2005.04.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/20/2005] [Indexed: 11/20/2022]
Abstract
In this study, the performance of the MicroFoss system (Foss, Spain) for the enumeration of Escherichia coli in water samples was evaluated. One hundred and eighty-five samples were analysed both by MicroFoss assay and culture isolation on Tryptone-Bile X-glucuronide agar (TBX), and the correlation coefficient obtained was 0.92. The analysis of 28 new samples using both methods showed a statistically significant relationship at the 99.5% confidence level between log colony forming units obtained by MicroFoss assay and those obtained using growth on TBX agar. Nevertheless, when the level of sample contamination was low, the variability was high. In conclusion, the MicroFoss system is a rapid and simple alternative method for the enumeration of E. coli in water although discordance between the results using these methods in samples with low counts could limit its use for the study of clean water such as potable water.
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Affiliation(s)
- V Mellado
- Labaqua, Pol. Ind. Las Atalayas, C/Del Dracma 16-18, 03114 Alicante, Spain
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86
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Garcia-Armisen T, Lebaron P, Servais P. beta-d-glucuronidase activity assay to assess viable Escherichia coli abundance in freshwaters. Lett Appl Microbiol 2005; 40:278-82. [PMID: 15752218 DOI: 10.1111/j.1472-765x.2005.01670.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIMS The relationships between the beta-D-glucuronidase (GLUase) activity, the abundance of culturable Escherichia coli and the number of viable E. coli were investigated in river and wastewater samples. METHODS AND RESULTS GLUase activity was measured as the rate of hydrolysis of 4-methylumbelliferyl-beta-D-glucuronide. Culturable E. coli were enumerated by the most probale number (MPN) microplate method. Viable E. coli were estimated by fluorescent in situ hybridization (FISH) coupled with a procedure of viability testing (DVC-FISH procedure). Significant correlations were found between the log of GLUase activity and both, the log culturable E. coli and the log of viable E. coli. CONCLUSIONS GLUase activity per viable E. coli gave a broadly constant value from low to highly contaminated waters while GLUase activity per culturable E. coli strongly increased at low contaminated waters because of an underestimation of the number of active E. coli by the culture-based method. SIGNIFICANCE AND IMPACT OF THE STUDY GLUase activity is a reliable parameter for the rapid quantification of viable E. coli in waters.
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Affiliation(s)
- T Garcia-Armisen
- Ecologie des Systèmes Aquatiques, Université Libre de Bruxelles, Campus de la Plaine, Bruxelles, Belgium
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87
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Abstract
In this study, optical spectroscopy was used to monitor a chromogenic, enzyme-substrate reaction for the rapid identification of Enterococcus faecalis. The detection system, comprising a miniature spectrophotometer and an accompanying data acquisition system, was placed in an incubator. During testing, a 3-ml test sample was placed in a cuvette within the spectrophotometer. This permitted online, real-time, and remote analysis of spectral signature needed to monitor the bacteria. It was observed that the absorption peak intensity increased conspicuously 3.5 h after inoculation and through the entire period of testing. A linear-regression analysis demonstrated a significant correlation between the increase in absorption peak intensity at 610 nm (r = 0.9389) and 653 nm (r = 0.9387) with the formation of colony-forming units. Optical spectroscopy-based sensing systems can pave the way for rapid, nonlaboratory-based approaches to monitor microbial status quantitatively and qualitatively from clinical samples.
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Affiliation(s)
- A Kishen
- Department of Restorative Dentistry, Faculty of Dentistry, National University of Singapore.
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88
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Iversen C, Druggan P, Forsythe S. A selective differential medium for Enterobacter sakazakii, a preliminary study. Int J Food Microbiol 2004; 96:133-9. [PMID: 15364468 DOI: 10.1016/j.ijfoodmicro.2004.01.024] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2003] [Revised: 12/02/2003] [Accepted: 01/05/2004] [Indexed: 11/17/2022]
Abstract
Enterobacter sakazakii can cause fatal invasive infection of neonates associated with the presence of this organism in powdered infant milk formula. A new chromogenic medium (Druggan-Forsythe-Iversen agar, DFI) is described for the selective detection of this emergent pathogen. The medium is based on the alpha-glucosidase reaction which is detected using 5-bromo-4-chloro-3-indolyl-alpha,D-glucopyranoside (XalphaGlc). Ent. sakazakii hydrolyses this substrate to an indigo pigment, producing blue-green colonies on this medium. DFI was compared with the current method of detection on violet red bile glucose agar (VRBGA) followed by pigment production on tryptone soy agar (TSA) after 48-72 h at 25 degrees C and subsequent biochemical profile determination using Biomerieux API20E. Ninety-five clinical and food strains of Ent. sakazakii were detected on the DFI chromogenic medium 2 days sooner than the alternative method. The characteristics of 148 strains representing 17 genera of non-Ent. sakazakii Enterobacteriaceae were compared using the two methods. Only 16/18 Escherichia vulneris strains, 2/3 strains of Pantoea spp. and 1/8 Citrobacter koseri strains gave false positive results on DFI agar. Eight alpha-glucosidase positive strains were identified as Pantoea using their API20E biochemical profile, but had higher percentage identification as Ent. sakazakii using ID32E. Therefore the DFI medium enables the detection of Ent. sakazakii within mixed cultures of Enterobacteriaceae, whereas the organism could be missed when using VRBGA since the latter is a general Enterobacteriaceae selective medium. In addition, the common use of API20E to check yellow pigmented colonies on TSA may lead to false negative results and consequently the acceptance of a batch of infant formula milk (IFM) that contains Ent. sakazakii.
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Affiliation(s)
- Carol Iversen
- School of Science, The Nottingham Trent University, Clifton Lane, Nottingham, NG11 8NS, UK
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89
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Ruiz G, Uría MJ, Rico A, Ladrón de Guevara C. [Evaluation of xylose galactosidase (XG) culture medium for the isolation of enteropathogens]. Enferm Infecc Microbiol Clin 2004; 22:381-4. [PMID: 15355767 DOI: 10.1016/s0213-005x(04)73120-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
INTRODUCTION The chromogenic medium, XG, was evaluated and compared to conventional media for the isolation of Salmonella spp., Shigella spp., Yersinia enterocolitica and Aeromonas spp. METHODS A total of 1226 human stool samples were inoculated on XG, MacConkey agar, Salmonella-Shigella agar (SS), selenite broth, blood-ampicillin agar and cefsulodin-Irgasan-novobiocin agar (CIN). RESULTS The 235 positive cultures included the following: 229 Salmonella spp., 3 Shigella spp., 2 Yersinia enterocolitica and one Aeromonas spp. Among the 229 containing Salmonella spp., 100 were detected on both XG and conventional media and the 129 remaining were detected only on conventional media; recovery of Salmonella spp. on conventional media was significantly higher with respect to XG medium (p < 0.005). The 3 isolates of Shigella spp. were obtained on XG, the 2 isolates of Yersinia enterocolitica were recovered on CIN agar and the single isolate of Aeromonas spp. was obtained both on XG and blood-ampicillin agar. Colonies suspected to be some of the enteropathogens investigated were present in 791 of the negative stool samples. Among these false-positives 441 (35.9%) were obtained from XG, 142 (11.6%) after selenite enrichment, 132 (10.8%) from MacConkey agar and 76 (6.2%) from SS agar. Most of the false-positive isolates obtained on XG medium were consistent with Salmonella spp. (n = 408). CONCLUSIONS XG chromogenic medium showed low sensitivity (64%) and specificity (69%) for the detection of Salmonella spp. Recovery of Shigella spp. on XG medium in three samples may have been due to the immediate processing of the samples. We conclude that XG chromogenic medium can not be recommended as an alternative to currently used conventional media.
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Affiliation(s)
- Guillermo Ruiz
- Servicio de Microbiología y Parasitología Clínica, Hospital Universitario La Paz, Madrid, Spain
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90
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Gracias KS, McKillip JL. A review of conventional detection and enumeration methods for pathogenic bacteria in food. Can J Microbiol 2004; 50:883-90. [PMID: 15644905 DOI: 10.1139/w04-080] [Citation(s) in RCA: 208] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
With continued development of novel molecular-based technologies for rapid, high-throughput detection of foodborne pathogenic bacteria, the future of conventional microbiological methods such as viable cell enumeration, selective isolation of bacteria on commercial media, and immunoassays seems tenuous. In fact, a number of unique approaches and variations on existing techniques are currently on the market or are being implemented that offer ease of use, reliability, and low cost compared with molecular tools. Approaches that enhance recovery of sublethally injured bacteria, differentiation among species using fluorogenics or chromogenics, dry plate culturing, differentiation among bacteria of interest using biochemical profiling, enumeration using impedence technology, techniques to confirm the presence of target pathogens using immunological methods, and bioluminescence applications for hygiene monitoring are summarized here and discussed in relation to their specific advantages or disadvantages when implemented in a food microbiology setting.Key words: food pathogen, detection, enumeration methods, food safety.
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Affiliation(s)
- Kiev S Gracias
- Department of Biology, Ball State University, Muncie, IN 47306, USA
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91
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OGIHARA H, OGAWA M, SKURA BJ, NAKAI S. Evaluation of Chromogenic Enzyme Substrate Mediums, Chromocult Coliform Agar(CCA) and XM-G, by Detection of Freeze-, Heat-, High-Pressure-Injured Coliforms, and Coliforms in Food Samples. FOOD SCIENCE AND TECHNOLOGY RESEARCH 2004. [DOI: 10.3136/fstr.10.168] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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92
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Kwon NH, Kim SH, Kim JY, Lim JY, Kim JM, Jung WK, Park KT, Bae WK, Noh KM, Choi JW, Hur J, Park YH. Antimicrobial performance of alkaline ionic fluid (GC-100X) and its ability to remove Escherichia coli O157:H7 from the surface of tomatoes. J Food Prot 2003; 66:1604-10. [PMID: 14503713 DOI: 10.4315/0362-028x-66.9.1604] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
An efficacy test of GC-100X, a noncorrosive alkaline ionic fluid (pH 12) composed of free radicals and supplemented with xylitol, was carried out against six major foodborne pathogens-Staphylococcus aureus FRI 913, Salmonella enterica serovar Enteritidis ATCC 13076, S. enterica serovar Typhimurium DT104 Korean isolate, Vibrio parahaemolyticus ATCC 17803, Escherichia coli O157:H7 ATCC 43894, and Pseudomonas aeruginosa KCTC 1637-at three different temperatures (4, 25, and 36 degrees C) with or without organic load (2% yeast extract). Results revealed a more than 4-log10 (CFU/ml) reduction (1.0 x 10(4) CFU/ml reduction) against all pathogens reacted at 37 degrees C for 3 h in the absence of organic material. GC-100X solution diluted with an equal volume of distilled or standard hard water (300 ppm CaCO3) showed effective bactericidal activity, particularly against gram-negative bacteria. Washing efficacy of GC-100X solution was compared against E. coli O157:H7 on cherry tomato surfaces with those of a commercially used detergent and chlorine water (100 ppm). Viable cell counts of E. coli O157:H7 that had penetrated to the cores of tomatoes after sanitizing treatment revealed that GC-100X stock and its 5% diluted solutions had similar washing effects to 100-ppm chlorine water and were more effective than the other kitchen detergent. These results indicate that GC-100X has good bactericidal and sanitizing activities and is useful as a new sanitizer for food safety and kitchen hygiene.
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Affiliation(s)
- N H Kwon
- Department of Microbiology, College of Veterinary Medicine and School of Agricultural Biotechnology, Seoul National University, Shilim 9-Dong, Kwanak-Gu, Seoul, 151-742, Korea
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93
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Fallon D, Ackland G, Andrews N, Frodsham D, Howe S, Howells K, Nye KJ, Warren RE. A comparison of the performance of commercially available chromogenic agars for the isolation and presumptive identification of organisms from urine. J Clin Pathol 2003; 56:608-12. [PMID: 12890812 PMCID: PMC1770023 DOI: 10.1136/jcp.56.8.608] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AIMS To compare four media-UTI medium, BBL CHROMagar, CPS ID2, and Harlequin CLED-using a collection of fully characterised organisms and subsequent "field trial". METHODS Seven hundred and eighty seven fully characterised isolates (730 Gram negative bacteria, 47 Gram positive bacteria, and 10 yeasts) were used to test for accuracy of organism identification. To assess isolation rates and ability to detect mixed cultures, 1435 urine samples were cultured in the three best performing chromogenic media (UTI medium, BBL CHROMagar, and CPS ID2) and CLED. RESULTS The chromogenic agars differed in their accuracy of identification, with BBL CHROMagar performing best and Harlequin CLED performing least well. Similarly, BBL CHROMagar achieved a higher overall isolation rate than UTI medium and CPS ID2. When mixed growth was defined as greater than two organism types, BBL CHROMagar detected more mixed cultures than did UTI medium and CPS ID2, although the differences were not significant. When mixed growth was defined as greater than one organism type the increased number of mixed growths detected by BBL CHROMagar became significant, largely because of differences in enterococcal isolation rates. CONCLUSION The use of BBL CHROMagar, UTI medium, or CPS ID2 chromogenic agar as a replacement for CLED agar would improve the detection rate of contaminated urine samples. Enhanced identification helps to distinguish different species, facilitating the monitoring of bacterial resistance in support of the national antibiotic strategy. BBL CHROMagar gave the highest overall organism recovery rates, greatest ability to detect mixed cultures, and the most accurate identification of organisms.
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Affiliation(s)
- D Fallon
- Public Health Laboratory Service (Midlands), Group Headquarters, The Royal Shrewsbury Hospital, Mytton Oak Road, Shrewsbury SY3 8XQ, UK. PHLS Statistics Unit, 61 Colindale Ave, London NW9 5EQ, UK.
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94
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Cassar R, Cuschieri P. Comparison of Salmonella chromogenic medium with DCLS agar for isolation of Salmonella species from stool specimens. J Clin Microbiol 2003; 41:3229-32. [PMID: 12843068 PMCID: PMC165381 DOI: 10.1128/jcm.41.7.3229-3232.2003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Salmonella chromogenic medium (SCM; Oxoid, Basingstoke, United Kingdom), a new selective chromogenic medium, was compared to DCLS agar (Oxoid) for the detection and presumptive identification of Salmonella species from stool samples. This medium contains two chromogenic substrates, Magenta-cap (5-bromo-6-chloro-3-indolylcaprylate), which is hydrolyzed by Salmonella species to give magenta colonies, and X-Gal (5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside), which is incorporated to visualize beta-D-galactosidase-producing organisms as blue colonies. Thus, non-Salmonella organisms appear blue or are not stained by any of the chromogens of the medium. A total of 500 stool samples were investigated by plating them directly and after selenite enrichment on DCLS agar and SCM. A total of 44 Salmonella-positive stool samples were detected. The sensitivities for direct plating and after enrichment were 22.7 and 81.8%, respectively, for DCLS agar, and for SCM these values were 34.1 and 100%, respectively. The specificities for direct plating and after enrichment were 82.5 and 72.8%, respectively, for DCLS agar and 98.5 and 95.8%, respectively, for SCM. According to these results, the sensitivities of SCM and DCLS agar were comparable on primary plating. However, the sensitivity of SCM was significantly higher after enrichment. In addition, the specificity of SCM was also significantly higher than that of DCLS agar both before and after enrichment. On the basis of these results, SCM can be recommended for the isolation of Salmonella species from stool samples in preference to DCLS agar.
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Affiliation(s)
- Robert Cassar
- Bacteriology Laboratory, Pathology Department, St. Luke's Hospital, G'Mangia, Malta.
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95
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Jinneman KC, Hunt JM, Eklund CA, Wernberg JS, Sado PN, Johnson JM, Richter RS, Torres ST, Ayotte E, Eliasberg SJ, Istafanos P, Bass D, Kexel-Calabresa N, Lin W, Barton CN. Evaluation and interlaboratory validation of a selective agar for phosphatidylinositol-specific phospholipase C activity using a chromogenic substrate to detect Listeria monocytogenes from foods. J Food Prot 2003; 66:441-5. [PMID: 12636298 DOI: 10.4315/0362-028x-66.3.441] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Phosphatidylinositol-specific phospholipase C (PI-PLC) activity is a potential virulence factor and is exhibited only by the Listeria species Listeria monocytogenes and Listeria ivanovii. A chromogenic substrate for the direct detection of PI-PLC activity is available in a new medium (BCM L. monocytogenes plating agar). The use of a chromogenic substrate offers a mechanism with which to directly screen for L. monocytogenes and L. ivanovii other than the esculin used in Oxford (OXF) and Palcam (PAL) agars, which screen for all Listeria species. The specificity levels of BCM plating agar and of BCM confirmation and rhamnose agars were evaluated with 107 Listeria and 10 Bacillus species isolates. In addition, BCM L. monocytogenes plating agar was compared with standard Listeria selective agars (OXF and PAL agars) with regard to the recovery of L. monocytogenes from 2,000 food and environmental samples obtained from eight participating laboratories. A Listeria species was isolated from at least one of the agars in 209 analyses, and L. monocytogenes was isolated in 135 of these analyses. In 27 of the analyses in which L. monocytogenes was isolated, one or more of the selective differential agars used failed to isolate L. monocytogenes, and therefore the results of these analyses were discrepant. Relative to a reference method involving the use of all three agars (OXF, PAL, and BCM agars), the OXF-BCM, PAL-BCM, and OXF-PAL combinations had sensitivities of 99.3, 99.2, and 90.2%, respectively. In statistical analyses of the different combinations of agars, the OXF-BCM and BCM-PAL combinations were found to be superior to the OXF-PAL combination for the detection of L. monocytogenes.
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Affiliation(s)
- Karen C Jinneman
- Food and Drug Administration, Office of Regulatory Affairs, Pacific Regional Laboratory-Northwest, 22201 23rd Drive S.E., Bothell, Washington 98021, USA.
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96
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Frahm E, Obst U. Application of the fluorogenic probe technique (TaqMan PCR) to the detection of Enterococcus spp. and Escherichia coli in water samples. J Microbiol Methods 2003; 52:123-31. [PMID: 12401234 DOI: 10.1016/s0167-7012(02)00150-1] [Citation(s) in RCA: 174] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
A recent PCR detection technique (TaqMan) based on the 5'-3'-exonuclease activity of the Taq DNA polymerase was applied to the detection of indicator organisms in water samples. In this technique, an increasing fluorescence signal is measured online which enables direct assessment of results after PCR without additional detection steps. The test is completed within about 5 h. Two sets of primers and probes were designed and tested: a genus-specific assay for the detection of Enterococcus spp. based on 23S rRNA sequence and an Escherichia coli-specific assay based on the uidA gene sequence. Specificity of the assays was confirmed by testing strains of target bacteria and potential interfering microorganisms. Application of the tests to 55 natural water samples showed the need of an overnight enrichment step to achieve compliance with detection limits of existing regulations. Compared with a parallel microbiological examination of the samples, agreement was 96% with the Enterococcus assay and 98% with the E. coli assay. The rapidity and feasibility of the method point to benefits in drinking water analysis, particularly in emergency situations and, thus, to improved public health management.
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Affiliation(s)
- Edith Frahm
- Forschungszentrum Karlsruhe GmbH, ITC-WGT, Abt. Umweltmikrobiologie, PF 3640, D-76021 Karlsruhe, Germany.
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97
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Palacios E, Rodríguez-Granjer J, Sampedro A, Martínez-Brocal A, de la Rosa-Fraile M. [Use of MPO chromogenic culture medium for routine processing of urine cultures]. Enferm Infecc Microbiol Clin 2002; 20:388-90. [PMID: 12372235 DOI: 10.1016/s0213-005x(02)72825-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND The chromogenic culture medium, MPO, was compared to culture on CLED (cystein, lactose, electrolyte-deficient) agar for the detection, enumeration and identification of urinary tract pathogens. METHODS A total of 1,080 clinical urine specimens were assessed. All samples were inoculated in MPO and CLED using the calibrated loop method. RESULTS Among 145 positive urine samples, 171 strains of bacteria were isolated (111 Escherichia coli, 26 Enterococcus spp., 12 Proteus spp., 10 Enterobacteriaceae from the Klebsiella-Enterobacter-Serratia group, 5 Pseudomonas aeruginosa, 4 Streptococcus agalactiae, 3 Staphylococcus spp. and 4 Candida albicans. For all samples, enumeration of microorganisms was comparable with the two media studied. Identification was also similar, except for 6 cases in which Enterococcus spp. were only detected with the chromogenic medium. CONCLUSIONS Overall urine culture results with MPO chromogenic medium were similar to those obtained with CLED, making it a feasible alternative to the standard medium. Moreover, use of a chromogenic technique implies a significant reduction in workload, since additional tests to identify the microorganisms isolated are not needed in most cases.
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Affiliation(s)
- Elena Palacios
- Servicio de Microbiología. Hospital Virgen de las Nieves. Granada. España
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98
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Voitoux E, Lafarge V, Collette C, Lombard B. Applicability of the draft standard method for the detection of Escherichia coli O157 in dairy products. Int J Food Microbiol 2002; 77:213-21. [PMID: 12160081 DOI: 10.1016/s0168-1605(02)00110-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
According to the draft standard method, EN ISO 16654 for the detection of Escherichia coli O157 in foods, samples of milk products inoculated with E. coli O157 were cultured in modified Tryptone Soya Broth supplemented with novobiocin. After immuno-magnetic separation (IMS) of the micro-organisms with magnetic beads coated with an antibody against E. coli O157 (Dynabeads anti E. coli O157, Dynal), the enrichment broth was subcultured onto both Cefixim Tellurite Sorbitol MacConkey agar and CHROMagar O157. IMS alone appeared not to be very specific to E. coli O157; however, IMS combined with CT-SMAC plating enabled a greater exclusivity. The method displayed a low limit of detection (1-2 cfu/25 g) of E. coli O157 strains in milk products after only 6 h of incubation of the enrichment broth. However, the detection was affected by storage of the inoculum at 4 degrees C, and another 12 to 18 h of incubation was necessary to recover potentially stressed cells.
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Affiliation(s)
- Elodie Voitoux
- Agence Française de sécurité Sanitaire des Aliments, Laboratoire d'Etudes et de Recherches sur l'Hygiène et la Qualité des Aliments, Maisons-Alfort, France.
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Abstract
AIMS The purpose of this study was to develop a reliable molecular procedure for the detection of Escherichia coli in milk. METHODS AND RESULTS Robust and expeditious DNA extraction and PCR techniques were evaluated using Enzyme-Linked Immunosorbent Assay (ELISA) detection of biotin-labelled amplicons to facilitate optimal detection of E. coli DNA. CONCLUSIONS It was found that 5 E. coli colony-forming units (cfu) could be detected per PCR reaction using the PCR-ELISA system, equating to a sensitivity of detection of 100 E. coli cfu ml(-1) pasteurized milk. SIGNIFICANCE AND IMPACT OF THE STUDY This approach should facilitate evaluation of milk contamination and enable rapid detection of E. coli mastitis, leading to correct deployment of relevant antibiotic therapy and improved animal welfare.
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Affiliation(s)
- P Daly
- Department of Biology, National University of Ireland, Maynooth, Kildare, Ireland
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Fallon D, Andrews N, Frodsham D, Gee B, Howe S, Iliffe A, Nye KJ, Warren RE. A comparison of the performance of cystine lactose electrolyte deficient (CLED) agar with Oxoid chromogenic urinary tract infection (CUTI) medium for the isolation and presumptive identification of organisms from urine. J Clin Pathol 2002; 55:524-9. [PMID: 12101200 PMCID: PMC1769695 DOI: 10.1136/jcp.55.7.524] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/26/2002] [Indexed: 11/04/2022]
Abstract
AIMS As part of the UK antimicrobial resistance strategy and action plan, the Public Health Laboratory Service (PHLS) is required to collect antibiotic susceptibility data so that resistance trends and patterns can be monitored. Most laboratories report urine Gram negative isolates, as "coliforms" according to morphological appearance, but without an acceptable identification system the antimicrobial surveillance data will be meaningless. Commercially available identification systems tend to be expensive and time consuming. Chromogenic agars, which claim to improve the detection of mixed cultures and identification of organisms from urine, have now become available and may provide a cost effective alternative. The primary aim of this study was to compare the performance of cystine lactose electrolyte deficient (CLED) agar with a chromogenic agar (Oxoid urinary tract infection medium; CUTI) in terms of isolation rates and ability to detect mixed cultures. Secondary aims were to evaluate the correlation of "presumptive" identification of isolates from chromogenic media with that of two commercial identification systems and to appraise the sensitivity of the semiquantitative loop and filter paper strip culture techniques. METHOD One thousand, four hundred and sixty six urine samples were examined in four laboratories using the semiquantitative culture methods of 1 microl loop and filter paper strip. The degree of accuracy of organism identification was measured by comparing the presumptive identification using colony colour supplemented with simple bench tests, with identification obtained from two more complex commercial systems. RESULTS There was no significant difference between the performance of the loop and filter paper strip methods on the CLED agar, but the CUTI agar performed significantly better than the CLED agar for the detection of significant isolates and mixed cultures. This difference was greater using the loop method. Identification of the organisms using the commercial systems gave > 99% agreement and was therefore considered suitable as a standard against which to compare the presumptive CUTI identification. Using the manufacturer's colony colour criteria in combination with a bench indole test, the CUTI medium was 99% specific for Escherichia coli, although this was reduced to 97% if the indole test was omitted. Citrobacter spp were the most commonly misidentified organisms, giving false presumptive identification as E coli. By testing oxidase activity to differentiate Pseudomonas spp and the absence of indole production to support the identification of Proteus mirabilis, the CUTI medium provided a suitable identification for 86.8% of Gram negative isolates. The remaining 13.2% would require further identification. CONCLUSION CUTI medium improves the detection of mixed cultures, thereby improving the reliability of reporting of significant isolates when compared with CLED agar. When supplemented with simple bench tests it provides an identification system capable of speciating 86.8% of Gram negative isolates and providing a valuable cost effective mechanism for antimicrobial resistance surveillance.
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Affiliation(s)
- D Fallon
- Public Health Laboratory Service (Midlands), Group Headquarters, The Royal Shrewsbury Hospital, Mytton Oak Road, UK.
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