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Salazar JK, Fay M, Eckert C, Stewart D, Cranford V, Tortorello ML. Evaluation of Methods of Enrichment and Compositing of Environmental Samples for Detection of Listeria monocytogenes. J Food Prot 2021; 84:639-646. [PMID: 33232458 DOI: 10.4315/jfp-20-276] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 11/21/2020] [Indexed: 11/11/2022]
Abstract
ABSTRACT Various methods exist for the enrichment and detection of Listeria spp. and Listeria monocytogenes from environmental samples. Procedures for the compositing of environmental samples are not as well defined. In this study, different enrichment procedures involving buffered Listeria enrichment broth (BLEB), University of Vermont medium (UVM), and Fraser broth (FB) were evaluated to determine the limits of detection (LODs) for L. monocytogenes from culture and from swabs of stainless steel and to assess the efficacy of composite sampling by wet (pooling of primary enrichments) and dry (pooling of swabs) procedures. For detection of cells in pure culture, the computed values for the LOD at 95% probability (LOD95) using a single-step BLEB or two-step UVM-FB enrichment were 0.33 and 0.49 CFU/225 mL enrichment, respectively. No significant differences in detection were observed for procedures using either two-step BLEB-FB or UVM-FB enrichments for swabs of stainless steel when L. monocytogenes was inoculated at 2 to 6 log CFU; the LOD95 values were 3.82 and 3.62 log CFU per 4-in2 area, respectively. Wet compositing of L. monocytogenes from culture with and without romaine lettuce wash resident microbiota was conducted using BLEB-FB and UVM-FB enrichment methods; both allowed detection of the pathogen at ratios of 1:1, 1:2, 1:4, and 1:7 (1 positive sample to x negative samples) with no loss in sensitivity. From swabs of stainless steel, L. monocytogenes was detected similarly for both wet and dry composites of up to eight samples (1:7) with romaine lettuce wash. However, the BLEB-FB method allowed significantly faster detection (after 24 h of FB incubation) in composites of 1:4 and 1:7 samples compared with the UVM-FB method under the conditions tested. The results of this study provide data to evaluate the efficacies of the different enrichment procedures and aid in assessing the use of wet and dry compositing of environmental samples for use as part of a Listeria control plan in food production and processing facilities. HIGHLIGHTS
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Affiliation(s)
- Joelle K Salazar
- Division of Food Processing Science and Technology, U.S. Food and Drug Administration, 6502 South Archer Road, Bedford Park, Illinois 60501.,(ORCID: https://orcid.org/0000-0002-3587-7588 [J.K.S.])
| | - Megan Fay
- Division of Food Processing Science and Technology, U.S. Food and Drug Administration, 6502 South Archer Road, Bedford Park, Illinois 60501
| | - Christine Eckert
- Institute for Food Safety and Health, Illinois Institute of Technology, 6502 South Archer Road, Bedford Park, Illinois 60501; and
| | - Diana Stewart
- Division of Food Processing Science and Technology, U.S. Food and Drug Administration, 6502 South Archer Road, Bedford Park, Illinois 60501
| | - Vanessa Cranford
- Division of Produce Safety, U.S. Food and Drug Administration, 5001 Campus Drive, College Park, Maryland 20740, USA
| | - Mary Lou Tortorello
- Division of Food Processing Science and Technology, U.S. Food and Drug Administration, 6502 South Archer Road, Bedford Park, Illinois 60501
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Sheth I, Li F, Hur M, Laasri A, De Jesus AJ, Kwon HJ, Macarisin D, Hammack TS, Jinneman K, Chen Y. Comparison of three enrichment schemes for the detection of low levels of desiccation-stressed Listeria spp. from select environmental surfaces. Food Control 2018. [DOI: 10.1016/j.foodcont.2017.08.022] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Martínez-Gonzáles NE, Martínez-Chávez L, Martínez-Cárdenas C, Cabrera-Díaz E, Castillo A. The Polymyxin Ceftazidime Oxford Medium as an alternative selective and differential medium for isolation of Listeria monocytogenes from raw or unpasteurized food. Food Microbiol 2013; 38:44-51. [PMID: 24290624 DOI: 10.1016/j.fm.2013.07.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Revised: 07/11/2013] [Accepted: 07/17/2013] [Indexed: 11/18/2022]
Abstract
The Polymyxin Ceftazidime Oxford Medium (PCOM) was developed to recover Listeria monocytogenes from raw or unpasteurized foods. It contains esculin-ferric ammonium citrate as indicator system for Listeria growth, and ceftazidime and polymyxin B as selective agents, which are available in several Latin American countries. Comparison of PCOM, Modified Oxford Medium (MOX) and Tryptic Soy agar with 0.6% yeast extract (TSAYE) indicated that both selective media were equally effective at recovering four individual strains of L. monocytogenes (Scott A, V7, California and broccoli), and a mixture of these strains (LMM) (P > 0.05). The ability of PCOM, MOX, TSAYE and TSAYE supplemented with 4% NaCl to recover heat, acid and freeze-damaged LMM was similar for all media (P > 0.05). The PCOM proved to be effective at isolating colonies of LMM from inoculated raw beef chunks, unpasteurized orange juice, cabbage, and Mexican-style cheese by direct plating and by the US Department of Agriculture's Food Safety and Inspection Service enrichment method. Differentiation of L. monocytogenes colonies was easier on PCOM than on MOX for foods with high levels of background microbiota. Based on the evaluations performed on foods naturally contaminated with L. monocytogenes, PCOM was a more economical alternative than MOX for selective and differential isolation of Listeria from raw or unpasteurized foods.
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Affiliation(s)
- N E Martínez-Gonzáles
- Departamento de Farmacobiología, Universidad de Guadalajara, Boulevard Marcelino García Barragán 1451, Guadalajara, Jalisco 44430, Mexico
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Bruhn JB, Vogel BF, Gram L. Bias in the Listeria monocytogenes enrichment procedure: lineage 2 strains outcompete lineage 1 strains in University of Vermont selective enrichments. Appl Environ Microbiol 2005; 71:961-7. [PMID: 15691954 PMCID: PMC546678 DOI: 10.1128/aem.71.2.961-967.2005] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2004] [Accepted: 09/28/2004] [Indexed: 11/20/2022] Open
Abstract
Listeria monocytogenes can be isolated from a range of food products and may cause food-borne outbreaks or sporadic cases of listeriosis. L. monocytogenes is divided into three genetic lineages and 13 serotypes. Strains of three serotypes (1/2a, 1/2b, and 4b) are associated with most human cases of listeriosis. Of these, strains of serotypes 1/2b and 4b belong to lineage 1, whereas strains of serotype 1/2a and many other strains isolated from foods belong to lineage 2. L. monocytogenes is isolated from foods by selective enrichment procedures and from patients by nonselective methods. The aim of the present study was to investigate if the selective enrichment procedure results in a true representation of the subtypes of L. monocytogenes present in a sample. Eight L. monocytogenes strains (four lineage 1 strains and four lineage 2 strains) and one Listeria innocua strain grew with identical growth rates in the nonselective medium brain heart infusion (BHI), but differed in their growth rate in the selective medium University of Vermont medium I (UVM I). When coinoculated in UVM I, some strains completely outgrew other strains. This outcome was dependent on the lineage of L. monocytogenes rather than the individual growth rate of the strains. When inoculated at identical cell densities in UVM I, L. innocua outcompeted L. monocytogenes lineage 1 strains but not lineage 2 strains. In addition, lineage 2 L. monocytogenes strains outcompeted lineage 1 L. monocytogenes strains in all combinations tested, indicating a bias in strains selected by the enrichment procedures. Bias also occurred when coinoculating two lineage 2 or lineage 1 strains; however, it did not appear to correlate with origin (clinical versus food). Identical coinoculation experiments in BHI suggested that the selective compounds in UVM I and II influenced this bias. The results of the present study demonstrate that the selective procedures used for isolation of L. monocytogenes may not allow a true representation of the types present in foods. Our results could have a significant impact on epidemiological studies, as lineage 1 strains, which are often isolated from clinical cases of listeriosis, may be suppressed during enrichment by other L. monocytogenes lineages present in a food sample.
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Affiliation(s)
- Jesper Bartholin Bruhn
- Danish Institute for Fisheries Research, Department of Seafood Research, Søltofts Plads, c/o Technical University of Denmark, Bldg. 221, DK-2800 Kongens Lyngby, Denmark.
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Osborne CM, Bremer PJ. Development of a technique to quantify the effectiveness of enrichment regimes in recovering "stressed" Listeria cells. J Food Prot 2002; 65:1122-8. [PMID: 12117245 DOI: 10.4315/0362-028x-65.7.1122] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A rapid, reliable microwell plate method based on the most probable number (MPN) technique was used to determine the effectiveness of five enrichment regimes in the recovery and enumeration of Listeria spp. cells from five seafood products. The products tested were chosen to reflect conditions under which cells were exposed to the "stresses" associated with a variety of food-processing techniques, such as treatments involving an ethanol-based marinade, lowered pH (acetic acid), heat, sugar and salt brine (Gravilax), or frozen storage. Either Listeria monocytogenes and Listeria innocua were present in food samples as natural contaminants or L monocytogenes was added in the laboratory. Listeria repair broth (LRB), buffered Listeria enrichment broth, Listeria enrichment broth (LEB), Fraser broth, and University of Vermont modified Listeria enrichment broth were used to recover Listeria cells. The effectiveness of these enrichment regimes was found to be dependent on the type of stresses the cells had been exposed to. After exposure to ethanol, recovery of L monocytogenes cells was inhibited in enrichment regimes involving a nonselective period of resuscitation. On exposure to acetic acid, there were no significant differences (P < 0.05) between any of the regimes used. With heat-stressed cells, LRB recovered significantly fewer (P < 0.05) cells than did any other medium. On exposure to osmotic stress (elevated sugar and salt concentrations), LEB recovered the fewest cells. The largest number of cells was recovered from frozen fish (Hoki [Macruronus novazelandiae]) fillets with LRB. No single enrichment regime was consistently the most effective.
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Affiliation(s)
- C M Osborne
- Seafood Research Laboratory, New Zealand Institute for Crop & Food Research Limited, Nelson New Zealand, Port Nelson.
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Pinto M, Burri S, Mena C, Almeida G, Carneiro L, Teixeira P, Gibbs PA. Comparison of Oxford Agar, PALCAM and Listeria monocytogenes Blood Agar for the recovery of L. monocytogenes from foods and environmental samples. Food Control 2001. [DOI: 10.1016/s0956-7135(01)00052-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Comparison of PALCAM and modified Oxford plating media for isolation of Listeria species in poultry meat following UVM II or Fraser secondary enrichment broths. Food Microbiol 2001. [DOI: 10.1006/fmic.2001.0446] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Bremer PJ, Monk I, Osborne CM. Survival of Listeria monocytogenes attached to stainless steel surfaces in the presence or absence of Flavobacterium spp. J Food Prot 2001; 64:1369-76. [PMID: 11563514 DOI: 10.4315/0362-028x-64.9.1369] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Contaminated surfaces of food processing equipment are believed to be a significant source of Listeria monocytogenes to foods. However, very little is known about the survival of Listeria in processing environments. In a mixed bacterial biofilm of L. monocytogenes and Flavobacterium spp., the number of L. monocytogenes cells attaching to stainless steel increased significantly compared to when L. monocytogenes was in a pure culture. The L. monocytogenes cells in the mixed biofilms were also recoverable for significantly longer exposure periods. On colonized coupons held at 15 degrees C and 75% humidity, decimal reduction times were 1.2 and 18.7 days for L. monocytogenes in pure and mixed biofilms, respectively. With increasing exposure time, the proportion of cells that were sublethally injured (defined as an inability to grow on selective agar) increased from 8.1% of the recoverable cell population at day 0 to 91.4% after 40 days' exposure. At 4 and -20 degrees C, decimal reduction times for L. monocytogenes in pure culture were 2.8 and 1.4 days, respectively, and in mixed culture, 10.5 and 14.4 days, respectively. The enhanced colonization and survival of L. monocytogenes on "unclean" surfaces increase the persistence of this pathogen in food processing environments, while the increase in the percentage of sublethally injured cells in the population with time may decrease the ability of enrichment regimes to detect it.
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Affiliation(s)
- P J Bremer
- New Zealand Institute for Crop & Food Research Limited, Food Science, University of Otago, Dunedin.
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Comparison of two pre-enrichments broths for recovering Listeria spp. from salmon (Salmo salar) and salmon-trout (Oncorhynchus mykiss). Food Control 2001. [DOI: 10.1016/s0956-7135(01)00034-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Abstract
The heat resistance data on Listeria monocytogenes in culture media and foods are summarized. Most heat resistance data for foods have been obtained in dairy, meat, poultry, and egg products. Limited data have been published on seafood, fruits, and vegetables. The methodologies employed have evolved over time; hence data from earlier experiments are not directly comparable to more recent studies. Many factors influence the heat resistance of L. monocytogenes. Variation exists among different strains in their ability to withstand heat treatment. In addition, heat resistance is influenced by age of the culture, growth conditions, recovery media, and characteristics of foods such as salt content, a(w), acidity, and the presence of other inhibitors. Listeriae are more heat resistant than most other nonspore-forming foodborne pathogens, and thus, processing recommendations based on data from experiments with Salmonella spp. or pathogenic Escherichia coli may not be sufficient to eliminate similar numbers of L. monocytogenes. The data provided in this review may prove useful for food processors in determining appropriate times and temperatures for producing foods free of vegetative pathogens.
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Affiliation(s)
- M E Doyle
- Food Research Institute, University of Wisconsin, Madison 53706, USA
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Suh JH, Knabel SJ. Comparison of different enrichment broths and background flora for detection of heat-injured Listeria monocytogenes in whole milk. J Food Prot 2001; 64:30-6. [PMID: 11198438 DOI: 10.4315/0362-028x-64.1.30] [Citation(s) in RCA: 13] [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
Various primary enrichment broths, including University of Vermont medium (UVM), Listeria enrichment broth (LEB), modified LEB, and aerobic and anaerobic L-PALCAMY, were compared with aerobic and anaerobic Pennsylvania State University (PSU) broths for the detection of severely heat-injured (62.8 degrees C for 5, 10, or 15 min; no colony appearance after heat injury on aerobic Trypticase soy agar containing 0.6% yeast extract and modified Oxford medium) Listeria monocytogenes Scott A. Anaerobic conditions were produced by adding L-cysteine and then purging the headspace with N2. The effect of uninjured background flora (10(3) CFU/ml of Enterococcus faecium) on frequency of detection was examined. Anaerobic PSU broth resulted in the lowest false-positive rate and the highest frequency of detection of severely heat-injured L. monocytogenes compared with UVM, LEB, and modified LEB (P < 0.05). The presence of E. faecium significantly enhanced the detection of heat-injured (10 min at 62.8 degrees C) L. monocytogenes in aerobic and anaerobic PSU and aerobic and anaerobic L-PALCAMY broths (P < 0.05). The highest concentration of uninjured E. faecium (>10(6) CFU/ml) inhibited the detection of heat-injured L. monocytogenes (P < 0.05). A heat-resistant, LiCl-tolerant Lactobacillus isolate from raw milk increased the rate of both false-positive and false-negative reactions.
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Affiliation(s)
- J H Suh
- Department of Food Science, The Pennsylvania State University, University Park 16802, USA
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Suh JH, Knabel SJ. Comparison of different reducing agents for enhanced detection of heat-injured Listeria monocytogenes. J Food Prot 2000; 63:1058-63. [PMID: 10945581 DOI: 10.4315/0362-028x-63.8.1058] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The effect of different reducing agents (L-cysteine, Oxyrase, and Enterococcus faecium) and their combinations on the detection of heat-injured (62.8 degrees C, 7.5 min or 10 min) Listeria monocytogenes was examined. The incorporation of L-Cysteine (0.5 g/liter) yielded higher percentage detection than any of the other reducing agents (P < 0.05). The combination of Oxyrase (10 U/ml) and E. faecium (10(3) CFU/ml) synergistically enhanced the detection of L. monocytogenes heat-injured for 10 min at 62.8 degrees C (P < 0.05). Simultaneous addition of L-cysteine (0.5 g/liter) and Oxyrase (10 U/ml) significantly lowered the recovery of heat-injured L. monocytogenes (P < 0.05). Higher activities of Oxyrase (50 U/ml) inhibited the detection of heat-injured L. monocytogenes (P < 0.05). The rates of depletion of relative percentage O2 were in the order: L-cysteine (0.5 g/liter; 6.63%/ min) > Oxyrase (10 U/ml; 5.00%/min) > E. faecium (10(8) CFU/ml; 1.66%/min) > E. faecium (10(3) CFU/ml; 0.20%/min). The final levels of redox potential (Eh) achieved were -110.5 mV, -100 mV, -83.5 mV, and -25 mV for E. faecium (10(8) CFU/ml), L-cysteine, Oxyrase, and E. faecium (10(3) CFU/ml), respectively.
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Affiliation(s)
- J H Suh
- Department of Biotechnology, Yonsei University, South Korea
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Duarte G, Vaz-Velho M, Capell C, Gibbs P. Efficiency of four secondary enrichment protocols in differentiation and isolation of Listeria spp. and Listeria monocytogenes from smoked fish processing chains. Int J Food Microbiol 1999; 52:163-8. [PMID: 10733247 DOI: 10.1016/s0168-1605(99)00121-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Four secondary enrichment protocols (conventional methods: UVM II, Fraser 24 h and Fraser 48 h: Impedimetric method: Listeria electrical detection medium) were studied for their ability to isolate Listeria spp. and Listeria monocytogenes from fish and environmental samples collected along the processing chain of cold-smoked fish. From all methods, Listeria spp. and L. monocytogenes were respectively present in 56 and 34 of 315 samples analysed. Fraser broth incubated for 48 h gave the fewest false negative Listeria spp. results [4/56; (7.1%)], but concurrently only 15/34 (44.1%) samples were correctly identified as containing L. monocytogenes, Listeria electrical detection (LED) medium detected only 36/56 (64.3%) Listeria spp. positive samples. Despite this lower isolation rate, LED identified 20/34 (58.8%) L. monocytogenes positive samples correctly and gave fewer false positive results. The overall conclusion was that more than one isolation method is needed to accurately estimate L. monocytogenes contamination rates.
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Affiliation(s)
- G Duarte
- Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Porto, Portugal.
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WILLIAMS ROBERTC, GOLDEN DAVIDA. SUITABILITY OF SELECTIVE MEDIA FOR RECOVERY AND ENUMERATION OF SUBLETHALLY HEAT- AND ACID-INJURED LISTERIA MONOCYTOGENES. ACTA ACUST UNITED AC 1998. [DOI: 10.1111/j.1745-4581.1998.tb00211.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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