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Chen Y, Pouillot R, S Burall L, Strain EA, Van Doren JM, De Jesus AJ, Laasri A, Wang H, Ali L, Tatavarthy A, Zhang G, Hu L, Day J, Sheth I, Kang J, Sahu S, Srinivasan D, Brown EW, Parish M, Zink DL, Datta AR, Hammack TS, Macarisin D. Comparative evaluation of direct plating and most probable number for enumeration of low levels of Listeria monocytogenes in naturally contaminated ice cream products. Int J Food Microbiol 2016; 241:15-22. [PMID: 27741432 DOI: 10.1016/j.ijfoodmicro.2016.09.021] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Revised: 07/11/2016] [Accepted: 09/24/2016] [Indexed: 11/25/2022]
Abstract
A precise and accurate method for enumeration of low level of Listeria monocytogenes in foods is critical to a variety of studies. In this study, paired comparison of most probable number (MPN) and direct plating enumeration of L. monocytogenes was conducted on a total of 1730 outbreak-associated ice cream samples that were naturally contaminated with low level of L. monocytogenes. MPN was performed on all 1730 samples. Direct plating was performed on all samples using the RAPID'L.mono (RLM) agar (1600 samples) and agar Listeria Ottaviani and Agosti (ALOA; 130 samples). Probabilistic analysis with Bayesian inference model was used to compare paired direct plating and MPN estimates of L. monocytogenes in ice cream samples because assumptions implicit in ordinary least squares (OLS) linear regression analyses were not met for such a comparison. The probabilistic analysis revealed good agreement between the MPN and direct plating estimates, and this agreement showed that the MPN schemes and direct plating schemes using ALOA or RLM evaluated in the present study were suitable for enumerating low levels of L. monocytogenes in these ice cream samples. The statistical analysis further revealed that OLS linear regression analyses of direct plating and MPN data did introduce bias that incorrectly characterized systematic differences between estimates from the two methods.
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Affiliation(s)
- Yi Chen
- Office of Regulatory Science, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD 20740, USA.
| | - Régis Pouillot
- Office of Analytics and Outreach, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD 20740, USA
| | - Laurel S Burall
- Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, Food and Drug Administration, Laurel, MD 20708, USA
| | - Errol A Strain
- Office of Analytics and Outreach, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD 20740, USA
| | - Jane M Van Doren
- Office of Analytics and Outreach, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD 20740, USA
| | - Antonio J De Jesus
- Office of Regulatory Science, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD 20740, USA
| | - Anna Laasri
- Office of Regulatory Science, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD 20740, USA
| | - Hua Wang
- Office of Regulatory Science, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD 20740, USA
| | - Laila Ali
- Office of Regulatory Science, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD 20740, USA
| | - Aparna Tatavarthy
- Office of Regulatory Science, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD 20740, USA
| | - Guodong Zhang
- Office of Regulatory Science, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD 20740, USA
| | - Lijun Hu
- Office of Regulatory Science, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD 20740, USA
| | - James Day
- Office of Regulatory Science, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD 20740, USA
| | - Ishani Sheth
- Office of Regulatory Science, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD 20740, USA
| | - Jihun Kang
- Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, Food and Drug Administration, Laurel, MD 20708, USA
| | - Surasri Sahu
- Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, Food and Drug Administration, Laurel, MD 20708, USA
| | - Devayani Srinivasan
- Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, Food and Drug Administration, Laurel, MD 20708, USA
| | - Eric W Brown
- Office of Regulatory Science, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD 20740, USA
| | - Mickey Parish
- Office of the Center Director, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD 20740, USA
| | - Donald L Zink
- Office of the Center Director, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD 20740, USA
| | - Atin R Datta
- Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, Food and Drug Administration, Laurel, MD 20708, USA
| | - Thomas S Hammack
- Office of Regulatory Science, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD 20740, USA
| | - Dumitru Macarisin
- Office of Regulatory Science, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD 20740, USA
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Luedtke BE, Bosilevac JM. Comparison of methods for the enumeration of enterohemorrhagic Escherichia coli from veal hides and carcasses. Front Microbiol 2015; 6:1062. [PMID: 26483780 PMCID: PMC4586433 DOI: 10.3389/fmicb.2015.01062] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 09/15/2015] [Indexed: 11/13/2022] Open
Abstract
The increased association of enterohemorrhagic Escherichia coli (EHEC) with veal calves has led the United States Department of Agriculture Food Safety and Inspection Service to report results of veal meat contaminated with the Top 7 serogroups separately from beef cattle. However, detection methods that can also provide concentration for determining the prevalence and abundance of EHEC associated with veal are lacking. Here we compared the ability of qPCR and a molecular based most probable number assay (MPN) to detect and enumerate EHEC from veal hides at the abattoir and the resulting pre-intervention carcasses. In addition, digital PCR (dPCR) was used to analyze select samples. The qPCR assay was able to enumerate total EHEC in 32% of the hide samples with a range of approximately 34 to 91,412 CFUs/100 cm2 (95% CI 4-113,460 CFUs/100 cm2). Using the MPN assay, total EHEC was enumerable in 48% of the hide samples and ranged from approximately 1 to greater than 17,022 CFUs/100 cm2 (95% CI 0.4–72,000 CFUs/100 cm2). The carcass samples had lower amounts of EHEC with a range of approximately 4–275 CFUs/100 cm2 (95% CI 3–953 CFUs/100 cm2) from 17% of samples with an enumerable amount of EHEC by qPCR. For the MPN assay, the carcass samples ranged from 0.1 to 1 CFUs/100 cm2 (95% CI 0.02–4 CFUs/100 cm2) from 29% of the samples. The correlation coefficient between the qPCR and MPN enumeration methods indicated a moderate relation (R2 = 0.39) for the hide samples while the carcass samples had no relation (R2 = 0.002), which was likely due to most samples having an amount of total EHEC below the reliable limit of quantification for qPCR. Interestingly, after enrichment, 81% of the hide samples and 94% of the carcass samples had a detectable amount of total EHEC by qPCR. From our analysis, the MPN assay provided a higher percentage of enumerable hide and carcass samples, however determining an appropriate dilution range and the limited throughput offer additional challenges.
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Affiliation(s)
- Brandon E Luedtke
- U. S. Department of Agriculture, Agricultural Research Service, Roman L. Hruska U. S. Meat Animal Research Center Clay Center, NE, USA
| | - Joseph M Bosilevac
- U. S. Department of Agriculture, Agricultural Research Service, Roman L. Hruska U. S. Meat Animal Research Center Clay Center, NE, USA
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Noll LW, Shridhar PB, Shi X, An B, Cernicchiaro N, Renter DG, Nagaraja TG, Bai J. A Four-Plex Real-Time PCR Assay, Based on rfbE, stx1, stx2, and eae Genes, for the Detection and Quantification of Shiga Toxin-Producing Escherichia coli O157 in Cattle Feces. Foodborne Pathog Dis 2015; 12:787-94. [PMID: 26317538 DOI: 10.1089/fpd.2015.1951] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Several real-time polymerase chain reaction (PCR) assays have been developed to detect and quantify Shiga toxin-producing Escherichia coli (STEC) O157:H7, but none have targeted the O-antigen specific gene (rfbEO157) in combination with the three major virulence genes, stx1, stx2, and eae. Our objectives were to develop and validate a four-plex, quantitative PCR (mqPCR) assay targeting rfbE(O157), stx1, stx2, and eae for the detection and quantification of STEC O157 in cattle feces, and compare the applicability of the assay to detect STEC O157 to a culture method and conventional PCR (cPCR) targeting the same four genes. Specificity of the mqPCR assay to differentially detect the four genes was confirmed with strains of O157 and non-O157 STEC with different profiles of target genes. In cattle feces spiked with pure cultures, detection limits were 2.8×10(4) and 2.8×10(0) colony-forming units/g before and after enrichment, respectively. Detection of STEC O157 in feedlot cattle fecal samples (n=278) was compared between mqPCR, cPCR, and a culture method. The mqPCR detected 48.9% (136/278) of samples as positive for E. coli O157. Of the 100 samples that were randomly picked from 136 mqPCR-positive samples, 35 and 48 tested positive by cPCR and culture method, respectively. Of the 100 samples randomly chosen from 142 mqPCR-negative samples, all were negative by cPCR, but 21 samples tested positive by the culture method. McNemar's chi-square tests indicated significant disagreement between the proportions of positive samples detected by the three methods. In conclusion, the mqPCR assay that targets four genes is a novel and more sensitive method than the cPCR or culture method to detect STEC O157 in cattle feces. However, the use of real-time PCR as a screening method to identify positive samples and then subjecting only positive samples to a culture method may underestimate the presence of STEC O157 in fecal samples.
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Affiliation(s)
- Lance W Noll
- 1 Department of Diagnostic Medicine/Pathobiology, Kansas State University , Manhattan, Kansas
| | - Pragathi B Shridhar
- 1 Department of Diagnostic Medicine/Pathobiology, Kansas State University , Manhattan, Kansas
| | - Xiaorong Shi
- 1 Department of Diagnostic Medicine/Pathobiology, Kansas State University , Manhattan, Kansas
| | - Baoyan An
- 2 Department of Veterinary Diagnostic Laboratory, College of Veterinary Medicine, Kansas State University , Manhattan, Kansas
| | - Natalia Cernicchiaro
- 1 Department of Diagnostic Medicine/Pathobiology, Kansas State University , Manhattan, Kansas
| | - David G Renter
- 1 Department of Diagnostic Medicine/Pathobiology, Kansas State University , Manhattan, Kansas
| | - Tiruvoor G Nagaraja
- 1 Department of Diagnostic Medicine/Pathobiology, Kansas State University , Manhattan, Kansas
| | - Jianfa Bai
- 2 Department of Veterinary Diagnostic Laboratory, College of Veterinary Medicine, Kansas State University , Manhattan, Kansas
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Development of a quantitative real time PCR assay to detect and enumerate Escherichia coli O157 and O26 serogroups in bovine recto-anal swabs. J Microbiol Methods 2015; 114:9-15. [DOI: 10.1016/j.mimet.2015.04.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 04/16/2015] [Accepted: 04/16/2015] [Indexed: 01/29/2023]
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Jacob ME, Bai J, Renter DG, Rogers AT, Shi X, Nagaraja TG. Comparing real-time and conventional PCR to culture-based methods for detecting and quantifying Escherichia coli O157 in cattle feces. J Food Prot 2014; 77:314-9. [PMID: 24490927 DOI: 10.4315/0362-028x.jfp-13-304] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Detection of Escherichia coli O157 in cattle feces has traditionally used culture-based methods; PCR-based methods have been suggested as an alternative. We aimed to determine if multiplex real-time (mq) or conventional PCR methods could reliably detect cattle naturally shedding high (≥10(4) CFU/g of feces) and low (∼10(2) CFU/g of feces) concentrations of E. coli O157. Feces were collected from pens of feedlot cattle and evaluated for E. coli O157 by culture methods. Samples were categorized as (i) high shedders, (ii) immunomagnetic separation (IMS) positive after enrichment, or (iii) culture negative. DNA was extracted pre- and postenrichment from 100 fecal samples from each category (high shedder, IMS positive, culture negative) and subjected to mqPCR and conventional PCR assays based on detecting three genes, rfbE, stx1, and stx2. In feces from cattle determined to be E. coli O157 high shedders by culture, 37% were positive by mqPCR prior to enrichment; 85% of samples were positive after enrichment. In IMS-positive samples, 4% were positive by mqPCR prior to enrichment, while 43% were positive after enrichment. In culture-negative feces, 7% were positive by mqPCR prior to enrichment, and 40% were positive after enrichment. The proportion of high shedder-positive and culture-positive (high shedder and IMS) samples were significantly different from mqPCR-positive samples before and after enrichment (P < 0.01). Similar results were observed for conventional PCR. Our data suggest that mqPCR and conventional PCR are most useful in identifying high shedder animals and may not be an appropriate substitute to culture-based methods for detection of E. coli O157 in cattle feces.
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Affiliation(s)
- M E Jacob
- Department of Population Health and Pathobiology, North Carolina State University, 1060 William Moore Drive, College of Veterinary Medicine, Raleigh, North Carolina 27607, USA.
| | - J Bai
- Department of Diagnostic Medicine/Pathobiology, Kansas State University, 1800 Denison Avenue, Manhattan, Kansas 66506, USA
| | - D G Renter
- Department of Diagnostic Medicine/Pathobiology, Kansas State University, 1800 Denison Avenue, Manhattan, Kansas 66506, USA
| | - A T Rogers
- Department of Population Health and Pathobiology, North Carolina State University, 1060 William Moore Drive, College of Veterinary Medicine, Raleigh, North Carolina 27607, USA
| | - X Shi
- Department of Diagnostic Medicine/Pathobiology, Kansas State University, 1800 Denison Avenue, Manhattan, Kansas 66506, USA
| | - T G Nagaraja
- Department of Diagnostic Medicine/Pathobiology, Kansas State University, 1800 Denison Avenue, Manhattan, Kansas 66506, USA
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Jacob ME, Shi X, An B, Nagaraja TG, Bai J. Evaluation of a multiplex real-time polymerase chain reaction for the quantification of Escherichia coli O157 in cattle feces. Foodborne Pathog Dis 2011; 9:79-85. [PMID: 22047056 DOI: 10.1089/fpd.2011.0947] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Cattle are asymptomatic reservoirs for Escherichia coli O157, a major foodborne pathogen. The organism generally colonizes the hindgut of cattle and is shed in the feces at low concentrations. The objective of this research was to evaluate a multiplex, real-time polymerase chain reaction (mqPCR) assay for quantification of E. coli O157 in cattle feces using stx1, stx2, and rfbE gene targets. Primer efficiency and analytical sensitivity of the assay were evaluated with a single or pooled (five strain) culture of E. coli O157. In pure culture, the minimum detection limit of the assay was 1.4×10(3) CFU/mL and 3.6×10(3) CFU/mL for the single and five-strain mixture of E. coli O157, respectively. Diagnostic sensitivity was analyzed using DNA extracted from cattle feces spiked with E. coli O157. In feces spiked with the pooled mixture of five E. coli O157 strains, the minimum detection limit was 3.6×10(4) CFU/g. We also evaluated the assay with feces from cattle experimentally inoculated with E. coli O157 by comparing the results to a culture-based method. For the majority of samples tested, the concentration of E. coli O157 detected by the real-time and culture methods was within one log difference. However, the assay could only be evaluated for cattle shedding high concentrations of E. coli O157. In conclusion, the mqPCR quantifying E. coli O157 in cattle feces using stx1, stx2, and rfbE gene targets may have use in detecting and quantifying super shedders, but is not applicable for quantification in animals shedding low concentrations (10(2) to 10(3) CFU/g feces).
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Affiliation(s)
- Megan E Jacob
- Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA
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Stephens TP, McAllister TA, Stanford K. Perineal swabs reveal effect of super shedders on the transmission of Escherichia coli O157:H7 in commercial feedlots1. J Anim Sci 2009; 87:4151-60. [DOI: 10.2527/jas.2009-1967] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Thomson DU, Loneragan GH, Thornton AB, Lechtenberg KF, Emery DA, Burkhardt DT, Nagaraja TG. Use of a Siderophore Receptor and Porin Proteins-Based Vaccine to Control the Burden ofEscherichia coliO157:H7 in Feedlot Cattle. Foodborne Pathog Dis 2009; 6:871-7. [DOI: 10.1089/fpd.2009.0290] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Daniel U. Thomson
- Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas
| | - Guy H. Loneragan
- Department of Agricultural Sciences, West Texas A&M University, Canyon, Texas
| | - Ashley B. Thornton
- Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas
| | | | | | | | - Triuvoor G. Nagaraja
- Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas
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Jenkins M, Endale D, Fisher D, Gay P. Most probable number methodology for quantifying dilute concentrations and fluxes ofEscherichia coliO157:H7 in surface waters. J Appl Microbiol 2009; 106:572-9. [DOI: 10.1111/j.1365-2672.2008.04028.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Fox JT, Renter DG, Sanderson MW, Nutsch AL, Shi X, Nagaraja TG. Associations between the presence and magnitude of Escherichia coli O157 in feces at harvest and contamination of preintervention beef carcasses. J Food Prot 2008; 71:1761-7. [PMID: 18810859 DOI: 10.4315/0362-028x-71.9.1761] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
To quantify associations at slaughter between Escherichia coli O157 carcass contamination, fecal-positive animals, and high-shedding animals within truckloads of finished cattle, we sampled up to 32 cattle from each of 50 truckloads arriving at a commercial abattoir in the Midwest United States during a 5-week summer period. Carcass swab samples collected pre-evisceration and fecal samples collected postevisceration were matched within animals and analyzed for the presence of E. coli O157, using enrichment, immunomagnetic separation, and plating on selective media (IMS). In addition, a direct plating procedure was performed on feces to identify high-shedding animals. E. coli O157 was isolated from 39 (2.6%) of 1,503 carcass samples in 15 (30%) truckloads, and 127 (8.5%) of 1,495 fecal samples in 37 (74%) truckloads. Fifty-five (3.7%) high-shedding animals were detected from 26 (52%) truckloads. Truckload high-shedder (Spearman rank-order correlation coefficient [r(s)] = 0.68), IMS-positive (r(s) = 0.48), and combined fecal (r(s) = 0.61) prevalence were significantly correlated with carcass prevalence. The probability of isolating E. coli O157 from a carcass was not significantly associated with the high-shedder or fecal IMS status of the animal from which the carcass was derived. However, the probability of carcass contamination was significantly associated with all truckload-level measures of fecal E. coli O157, particularly whether or not a high shedder was present within the truckload (odds ratio = 16.2; 95% confidence interval, 6.3-43.6). Our results suggest that high shedders within a truckload at slaughter could be a target for mitigation strategies to reduce the probability of preevisceration carcass contamination.
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Affiliation(s)
- J T Fox
- Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas 66506-5606, USA
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