1
|
Use of Organic Acid Mixtures Containing 2-Hydroxy-4-(Methylthio) Butanoic Acid (HMTBa) to Mitigate Salmonella enterica, Shiga Toxin-Producing Escherichia coli (STEC) and Aspergillus flavus in Pet Food Kibbles. Animals (Basel) 2023; 13:ani13050877. [PMID: 36899734 PMCID: PMC10000158 DOI: 10.3390/ani13050877] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2023] [Revised: 02/17/2023] [Accepted: 02/24/2023] [Indexed: 03/06/2023] Open
Abstract
Post-processing operations of extruded pet food kibbles involve coating the product with fats and flavorings. These processes increase the risk for cross-contamination with food-borne pathogens such as Salmonella and Shiga toxin-producing Escherichia coli (STEC), and mycotoxin-producing molds such as Aspergillus spp. after the thermal kill step. In this study, the antimicrobial effects of two types of organic acid mixtures containing 2-hydroxy-4-(methylthio) butanoic acid (HMTBa), Activate DA™ and Activate US WD-MAX™, against Salmonella enterica, STEC and Aspergillus flavus when used as a coating on pet food kibbles were evaluated. Using canola oil and dry dog digest as fat and flavor coatings, the efficacy of Activate DA (HMTBa + fumaric acid + benzoic acid) at 0%, 1% and 2%, and Activate US WD-MAX (HMTBa + lactic acid + phosphoric acid) at 0%, 0.5% and 1% was tested on kibbles inoculated with a cocktail of S. enterica serovars (Enteritidis, Heidelberg and Typhimurium) or Shiga toxin-producing E. coli (STEC) serovars (O121, and O26) at 37 °C for 0, 12, 24, 48, 72 h, 30 and 60 days. Similarly, their efficacy was tested against A. flavus at 25 °C for 0, 3, 7, 14, 21, 28 and 35 days. Activate DA at 2% and Activate US WD-MAX at 1% reduced Salmonella counts by ~3 logs after 12 h and 4-4.6 logs after 24 h. Similarly, STEC counts were reduced by ~2 logs and 3 logs after 12 h and 24 h, respectively. Levels of A. flavus did not vary up to 7 days, and afterwards started to decline by >2 logs in 14 days, and up to 3.8-log reduction in 28 days for Activate DA and Activate US WD-MAX at 2% and 1%, respectively. The results suggest that the use of these organic acid mixtures containing HMTBa during kibble coating may mitigate post-processing enteric pathogen and mold contamination in pet food kibbles, with Activate US WD-MAX being effective at a lower concentration (0.5-1%) compared to Activate DA.
Collapse
|
2
|
Quantitative LAMP and PCR Detection of Salmonella in Chicken Samples Collected from Local Markets around Pathum Thani Province, Thailand. INTERNATIONAL JOURNAL OF FOOD SCIENCE 2020; 2020:8833173. [PMID: 32695808 PMCID: PMC7368944 DOI: 10.1155/2020/8833173] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 06/08/2020] [Accepted: 06/23/2020] [Indexed: 02/06/2023]
Abstract
Salmonella is a bacterium that infects people when they consume contaminated food or liquids. To prevent humans from becoming ill, it is useful to have an efficient method of detecting Salmonella before the disease is passed on through the food chain. In this research, the efficiency of Salmonella detection was compared using the following four methods: conventional loop-mediated isothermal amplification (LAMP), PCR, quantitative LAMP (qLAMP), and qPCR. The artificial infection of chicken samples started with incubating of 10 mL of 108 CFU of S. typhimurium for 6 hr. and enriching for 2 hr. to represent real contamination of the samples. The results show that the sensitivity of Salmonella DNA detection in PCR, qPCR, LAMP, and qLAMP were 50 ng, 5 ng, 50 pg, and and 500 fg, respectively. Thirty samples of 10 g chicken were collected from 10 markets in Pathum Thani, Thailand; then, the infection was detected. The conventional LAMP, qLAMP, and qPCR methods detected Salmonella in all the chicken samples. However, the conventional PCR method detected Salmonella infection in only eight of the samples. Overall, the qLAMP method had the highest sensitivity of Salmonella DNA detection.
Collapse
|
3
|
Zhuang L, Gong J, Ji Y, Tian P, Kong F, Bai H, Gu N, Zhang Y. Lateral flow fluorescent immunoassay based on isothermal amplification for rapid quantitative detection of Salmonella spp. Analyst 2020; 145:2367-2377. [PMID: 32031182 DOI: 10.1039/c9an02011j] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Salmonella spp. are zoonotic pathogens of substantial public health concern. To enable detection in the field or under instrument-free conditions, we developed a rapid and robust lateral flow fluorescent immunoassay based on strand exchange amplification (SEA-LFIA) for the quantitative detection of Salmonella spp. As far as we know, this work is the first report regarding the use of Bst DNA polymerase-assisted SEA for fluorescence sensing to detect Salmonella spp. The SEA method was further confirmed by enzymatic digestion and Sanger dideoxy sequencing. The specificity of SEA-LFIA assay was verified by 89 Salmonella strains (18 Salmonella reference strains and 71 clinical isolates) and 15 non-Salmonella reference strains (different genera). The sensitivity of SEA-LFIA assay was 6 × 100 CFU mL-1 of Salmonella pure culture or 3 × 104 CFU 25 g-1 of artificially spiked raw chicken meat. Using this assay, it was found that 37 (16%) of the 236 samples collected were positive, which was consistent with the results of conventional PCR. The cutoff value is 15 and SEA-LFIA assay only takes ∼30 min without high equipment and reagent cost. In addition, the proposed strategy can be easily extended by redesigning the corresponding amplification primers to detect target analytes. In conclusion, the optimized SEA-LFIA assay is an efficient and specific method for the detection of Salmonella spp., and can potentially serve as a new on-site diagnostic tool in life sciences.
Collapse
Affiliation(s)
- Linlin Zhuang
- State Key Laboratory of Bioelectronics, Jiangsu Key Laboratory for Biomaterials and Devices, School of Biological Science and Medical Engineering and Collaborative Innovation Center of Suzhou Nano Science and Technology, Southeast University, Nanjing 210096, P. R. China.
| | | | | | | | | | | | | | | |
Collapse
|
4
|
Ge B, Domesle KJ, Yang Q, Hammack TS, Wang SS, Deng X, Hu L, Zhang G, Hu Y, Lai X, Chou KX, Dollete JR, Hirneisen KA, La SP, Richter RS, Rai DR, Yousefvand AA, Park PK, Wu CH, Eames T, Kiang D, Sheng J, Wu D, Hahn L, Ledger L, Logie C, You Q, Slavic D, Cai H, Ayers SL, Young SR, Pamboukian R. Multi-Laboratory Validation of a Loop-Mediated Isothermal Amplification Method for Screening Salmonella in Animal Food. Front Microbiol 2019; 10:562. [PMID: 30984125 PMCID: PMC6447708 DOI: 10.3389/fmicb.2019.00562] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 03/05/2019] [Indexed: 11/17/2022] Open
Abstract
Loop-mediated isothermal amplification (LAMP) has gained wide popularity in the detection of Salmonella in foods owing to its simplicity, rapidity, and robustness. This multi-laboratory validation (MLV) study aimed to validate a Salmonella LAMP-based method against the United States Food and Drug Administration (FDA) Bacteriological Analytical Manual (BAM) Chapter 5 Salmonella reference method in a representative animal food matrix (dry dog food). Fourteen independent collaborators from seven laboratories in the United States and Canada participated in the study. Each collaborator received two sets of 24 blind-coded dry dog food samples (eight uninoculated; eight inoculated at a low level, 0.65 MPN/25 g; and eight inoculated at a high level, 3.01 MPN/25 g) and initiated the testing on the same day. The MLV study used an unpaired design where different test portions were analyzed by the LAMP and BAM methods using different preenrichment protocols (buffered peptone water for LAMP and lactose broth for BAM). All LAMP samples were confirmed by culture using the BAM method. BAM samples were also tested by LAMP following lactose broth preenrichment (paired samples). Statistical analysis was carried out by the probability of detection (POD) per AOAC guidelines and by a random intercept logistic regression model. Overall, no significant differences in POD between the Salmonella LAMP and BAM methods were observed with either unpaired or paired samples, indicating the methods were comparable. LAMP testing following preenrichment in buffered peptone water or lactose broth also resulted in insignificant POD differences (P > 0.05). The MLV study strongly supports the utility and applicability of this rapid and reliable LAMP method in routine regulatory screening of Salmonella in animal food.
Collapse
Affiliation(s)
- Beilei Ge
- Division of Animal and Food Microbiology, Office of Research, Center for Veterinary Medicine, United States Food and Drug Administration, Laurel, MD, United States
| | - Kelly J. Domesle
- Division of Animal and Food Microbiology, Office of Research, Center for Veterinary Medicine, United States Food and Drug Administration, Laurel, MD, United States
| | - Qianru Yang
- Division of Animal and Food Microbiology, Office of Research, Center for Veterinary Medicine, United States Food and Drug Administration, Laurel, MD, United States
| | - Thomas S. Hammack
- Office of Regulatory Science, Center for Food Safety and Applied Nutrition, United States Food and Drug Administration, College Park, MD, United States
| | - Shizhen S. Wang
- Office of Analytics and Outreach, Center for Food Safety and Applied Nutrition, United States Food and Drug Administration, College Park, MD, United States
| | - Xiaohong Deng
- Office of Regulatory Science, Center for Food Safety and Applied Nutrition, United States Food and Drug Administration, College Park, MD, United States
| | - Lijun Hu
- Office of Regulatory Science, Center for Food Safety and Applied Nutrition, United States Food and Drug Administration, College Park, MD, United States
| | - Guodong Zhang
- Office of Regulatory Science, Center for Food Safety and Applied Nutrition, United States Food and Drug Administration, College Park, MD, United States
| | - Yuan Hu
- Northeast Food and Feed Laboratory, Office of Regulatory Affairs, United States Food and Drug Administration, Jamaica, NY, United States
| | - Xiaokuang Lai
- Northeast Food and Feed Laboratory, Office of Regulatory Affairs, United States Food and Drug Administration, Jamaica, NY, United States
| | - Kyson X. Chou
- Pacific Southwest Food and Feed Laboratory, Office of Regulatory Affairs, United States Food and Drug Administration, Irvine, CA, United States
| | - Jan Ryan Dollete
- Pacific Southwest Food and Feed Laboratory, Office of Regulatory Affairs, United States Food and Drug Administration, Irvine, CA, United States
| | - Kirsten A. Hirneisen
- Pacific Southwest Food and Feed Laboratory, Office of Regulatory Affairs, United States Food and Drug Administration, Irvine, CA, United States
| | - Sammie P. La
- Pacific Southwest Food and Feed Laboratory, Office of Regulatory Affairs, United States Food and Drug Administration, Irvine, CA, United States
| | - Richelle S. Richter
- Pacific Southwest Food and Feed Laboratory, Office of Regulatory Affairs, United States Food and Drug Administration, Irvine, CA, United States
| | - Diyo R. Rai
- San Francisco Laboratory, Office of Regulatory Affairs, United States Food and Drug Administration, Alameda, CA, United States
| | - Azadeh A. Yousefvand
- San Francisco Laboratory, Office of Regulatory Affairs, United States Food and Drug Administration, Alameda, CA, United States
| | - Paul K. Park
- Food and Drug Laboratory Branch, California Department of Public Health, Richmond, CA, United States
| | - Cindy H. Wu
- Food and Drug Laboratory Branch, California Department of Public Health, Richmond, CA, United States
| | - Tameji Eames
- Food and Drug Laboratory Branch, California Department of Public Health, Richmond, CA, United States
| | - David Kiang
- Food and Drug Laboratory Branch, California Department of Public Health, Richmond, CA, United States
| | - Ju Sheng
- Office of Indiana State Chemist, Purdue University, West Lafayette, IN, United States
| | - Dancia Wu
- Office of Indiana State Chemist, Purdue University, West Lafayette, IN, United States
| | - Lori Hahn
- Animal Health Laboratory, University of Guelph, Guelph, ON, Canada
| | - Lisa Ledger
- Animal Health Laboratory, University of Guelph, Guelph, ON, Canada
| | - Cynthia Logie
- Animal Health Laboratory, University of Guelph, Guelph, ON, Canada
| | - Qiu You
- Animal Health Laboratory, University of Guelph, Guelph, ON, Canada
| | - Durda Slavic
- Animal Health Laboratory, University of Guelph, Guelph, ON, Canada
| | - Hugh Cai
- Animal Health Laboratory, University of Guelph, Guelph, ON, Canada
| | - Sherry L. Ayers
- Division of Animal and Food Microbiology, Office of Research, Center for Veterinary Medicine, United States Food and Drug Administration, Laurel, MD, United States
| | - Shenia R. Young
- Division of Animal and Food Microbiology, Office of Research, Center for Veterinary Medicine, United States Food and Drug Administration, Laurel, MD, United States
| | - Ruiqing Pamboukian
- Office of Regulatory Science, Office of Regulatory Affairs, United States Food and Drug Administration, Rockville, MD, United States
| |
Collapse
|
5
|
Hu L, Deng X, Brown EW, Hammack TS, Ma LM, Zhang G. Evaluation of Roka Atlas Salmonella method for the detection of Salmonella in egg products in comparison with culture method, real-time PCR and isothermal amplification assays. Food Control 2018. [DOI: 10.1016/j.foodcont.2018.06.039] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
|
6
|
Akyol I. Development and application of RTi-PCR method for common food pathogen presence and quantity in beef, sheep and chicken meat. Meat Sci 2018; 137:9-15. [DOI: 10.1016/j.meatsci.2017.11.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 10/22/2017] [Accepted: 11/01/2017] [Indexed: 10/18/2022]
|
7
|
Domesle KJ, Yang Q, Hammack TS, Ge B. Validation of a Salmonella loop-mediated isothermal amplification assay in animal food. Int J Food Microbiol 2017; 264:63-76. [PMID: 29121500 DOI: 10.1016/j.ijfoodmicro.2017.10.020] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 10/12/2017] [Accepted: 10/16/2017] [Indexed: 12/18/2022]
Abstract
Loop-mediated isothermal amplification (LAMP) has emerged as a promising alternative to PCR for pathogen detection in food testing and clinical diagnostics. This study aimed to validate a Salmonella LAMP method run on both turbidimetry (LAMP I) and fluorescence (LAMP II) platforms in representative animal food commodities. The U.S. Food and Drug Administration (FDA)'s culture-based Bacteriological Analytical Manual (BAM) method was used as the reference method and a real-time quantitative PCR (qPCR) assay was also performed. The method comparison study followed the FDA's microbiological methods validation guidelines, which align well with those from the AOAC International and ISO. Both LAMP assays were 100% specific among 300 strains (247 Salmonella of 185 serovars and 53 non-Salmonella) tested. The detection limits ranged from 1.3 to 28 cells for six Salmonella strains of various serovars. Six commodities consisting of four animal feed items (cattle feed, chicken feed, horse feed, and swine feed) and two pet food items (dry cat food and dry dog food) all yielded satisfactory results. Compared to the BAM method, the relative levels of detection (RLODs) for LAMP I ranged from 0.317 to 1 with a combined value of 0.610, while those for LAMP II ranged from 0.394 to 1.152 with a combined value of 0.783, which all fell within the acceptability limit (2.5) for an unpaired study. This also suggests that LAMP was more sensitive than the BAM method at detecting low-level Salmonella contamination in animal food and results were available 3days sooner. The performance of LAMP on both platforms was comparable to that of qPCR but notably faster, particularly LAMP II. Given the importance of Salmonella in animal food safety, the LAMP assays validated in this study holds great promise as a rapid, reliable, and robust method for routine screening of Salmonella in these commodities.
Collapse
Affiliation(s)
- Kelly J Domesle
- Division of Animal and Food Microbiology, Office of Research, Center for Veterinary Medicine, U.S. Food and Drug Administration, 8401 Muirkirk Road, Laurel, MD 20708, USA
| | - Qianru Yang
- Division of Animal and Food Microbiology, Office of Research, Center for Veterinary Medicine, U.S. Food and Drug Administration, 8401 Muirkirk Road, Laurel, MD 20708, USA
| | - Thomas S Hammack
- Division of Microbiology, Office of Regulatory Science, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, 5001 Campus Drive, College Park, MD 20740, USA
| | - Beilei Ge
- Division of Animal and Food Microbiology, Office of Research, Center for Veterinary Medicine, U.S. Food and Drug Administration, 8401 Muirkirk Road, Laurel, MD 20708, USA.
| |
Collapse
|
8
|
Yang Q, Domesle KJ, Wang F, Ge B. Rapid detection of Salmonella in food and feed by coupling loop-mediated isothermal amplification with bioluminescent assay in real-time. BMC Microbiol 2016; 16:112. [PMID: 27316515 PMCID: PMC4912795 DOI: 10.1186/s12866-016-0730-7] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Accepted: 06/06/2016] [Indexed: 11/15/2022] Open
Abstract
Background Salmonella is among the most significant pathogens causing food and feed safety concerns. This study examined the rapid detection of Salmonella in various types of food and feed samples by coupling loop-mediated isothermal amplification (LAMP) with a novel reporter, bioluminescent assay in real-time (BART). Performance of the LAMP-BART assay was compared to a conventional LAMP and the commercially available 3M Molecular Detection Assay (MDA) Salmonella. Results The LAMP-BART assay was 100 % specific among 178 strains (151 Salmonella and 27 non-Salmonella) tested. The detection limits were 36 cells per reaction in pure culture and 104 to 106 CFU per 25 g in spiked food and feed samples without enrichment, which were comparable to those of the conventional LAMP and 3M MDA Salmonella but 5–10 min faster. Ground turkey showed a strong inhibition on 3M MDA Salmonella, requiring at least 108 CFU per 25 g for detection. The correlation between Salmonella cell numbers and LAMP-BART signals was high (R2 = 0.941–0.962), suggesting good quantification capability. After 24 h enrichment, all three assays accurately detected 1 to 3 CFU per 25 g of Salmonella among five types of food (cantaloupe, ground beef, ground turkey, shell eggs, and tomato) and three types of feed (cattle feed, chicken feed, and dry dog food) examined. However, 101 CFU per 25 g was required for cattle feed when tested by 3M MDA Salmonella. Conclusions The Salmonella LAMP-BART assay was rapid, specific, sensitive, quantitative, and robust. Upon further validation, it may become a valuable tool for routine screening of Salmonella in various types of food and feed samples.
Collapse
Affiliation(s)
- Qianru Yang
- Division of Animal and Food Microbiology, Office of Research, Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, MD, 20708, USA.,Department of Food Science, Louisiana State University Agricultural Center, Baton Rouge, LA, 70803, USA
| | - Kelly J Domesle
- Division of Animal and Food Microbiology, Office of Research, Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, MD, 20708, USA
| | - Fei Wang
- Division of Animal and Food Microbiology, Office of Research, Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, MD, 20708, USA.,Department of Nutrition and Food Science, University of Maryland, College Park, MD, 20742, USA
| | - Beilei Ge
- Division of Animal and Food Microbiology, Office of Research, Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, MD, 20708, USA.
| |
Collapse
|
9
|
Heyse S, Hanna LF, Woolston J, Sulakvelidze A, Charbonneau D. Bacteriophage cocktail for biocontrol of Salmonella in dried pet food. J Food Prot 2015; 78:97-103. [PMID: 25581183 DOI: 10.4315/0362-028x.jfp-14-041] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Human salmonellosis has been associated with contaminated pet foods and treats. Therefore, there is interest in identifying novel approaches for reducing the risk of Salmonella contamination within pet food manufacturing environments. The use of lytic bacteriophages shows promise as a safe and effective way to mitigate Salmonella contamination in various food products. Bacteriophages are safe, natural, highly targeted antibacterial agents that specifically kill bacteria and can be targeted to kill food pathogens without affecting other microbiota. In this study, we show that a cocktail containing six bacteriophages had a broadspectrum activity in vitro against a library of 930 Salmonella enterica strains representing 44 known serovars. The cocktail was effective against 95% of the strains in this tested library. In liquid culture dose-ranging experiments, bacteriophage cocktail concentrations of ≥10(8) PFU/ml inactivated more than 90% of the Salmonella population (10(1) to 10(3) CFU/ml). Dried pet food inoculated with a mixture containing equal proportions of Salmonella serovars Enteritidis (ATCC 4931), Montevideo (ATCC 8387), Senftenberg (ATCC 8400), and Typhimurium (ATCC 13311) and then surface treated with the six-bacteriophage cocktail (≥2.5 ± 1.5 × 10(6) PFU/g) achieved a greater than 1-log (P < 0.001) reduction compared with the phosphate-buffered saline-treated control in measured viable Salmonella within 60 min. Moreover, this bacteriophage cocktail reduced natural contamination in samples taken from an undistributed lot of commercial dried dog food that tested positive for Salmonella. Our results indicate that bacteriophage biocontrol of S. enterica in dried pet food is technically feasible.
Collapse
Affiliation(s)
- Serena Heyse
- The Procter & Gamble Company, 8700 Mason-Montgomery Road, Mason, Ohio 45040, USA
| | - Leigh Farris Hanna
- The Procter & Gamble Company, 8700 Mason-Montgomery Road, Mason, Ohio 45040, USA
| | - Joelle Woolston
- Intralytix, Inc., 701 East Pratt Street, Baltimore, Maryland 21202, USA
| | | | - Duane Charbonneau
- The Procter & Gamble Company, 8700 Mason-Montgomery Road, Mason, Ohio 45040, USA.
| |
Collapse
|
10
|
Zhang G, Thau E, Brown EW, Hammack TS. Comparison of a novel strategy for the detection and isolation of Salmonella in shell eggs with the Food and Drug Administration Bacteriological Analytical Manual method. Poult Sci 2014; 92:3266-74. [PMID: 24235238 DOI: 10.3382/ps.2013-03380] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The current FDA Bacteriological Analytical Manual (BAM) method for the detection of Salmonella in eggs requires 2 wk to complete. The objective of this project was to improve the BAM method for the detection and isolation of Salmonella in whole shell eggs. A novel protocol, using 1,000 g of liquid eggs for direct preenrichment with 2 L of tryptic soy broth (TSB) followed by enrichment using Rappaport-Vassiliadis and Tetrathionate broths, was compared with the standard BAM method, which requires 96 h room temperature incubation of whole shell egg samples followed by preenrichment in TSB supplemented with FeSO4. Four Salmonella ser. Enteritidis (4 phage types) and one Salmonella ser. Heidelberg isolates were used in the study. Bulk inoculated pooled liquid eggs, weighing 52 or 56 kg (approximately 1,100 eggs) were used in each trial. Twenty 1,000-g test portions were withdrawn from the pooled eggs for both the alternative and the reference methods. Test portions were inoculated with Salmonella at 1 to 5 cfu/1,000 g eggs. Two replicates were performed for each isolate. In the 8 trials conducted with Salmonella ser. Enteritidis, the alternative method was significantly (P < 0.05) more productive than the reference method in 3 trials, and significantly (P < 0.05) less productive than the reference method in 1 trial. There were no significant (P < 0.05) differences between the 2 methods for the other 4 trials. For Salmonella ser. Heidelberg, combined data from 2 trials showed the alternative method was significantly (P < 0.05) more efficient than the BAM method. We have concluded that the alternative method, described herein, has the potential to replace the current BAM culture method for detection and isolation of Salmonella from shell eggs based on the following factors: 1) the alternative method is 4 d shorter than the reference method; 2) it uses regular TSB instead of the more complicated TSB supplemented with FeSO4; and 3) it was equivalent or superior to the reference method in 9 out of 10 trials for the detection of Salmonella in shell eggs.
Collapse
Affiliation(s)
- Guodong Zhang
- Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD 20740
| | | | | | | |
Collapse
|