scholarly journals Bias in the Listeria monocytogenes Enrichment Procedure: Lineage 2 Strains Outcompete Lineage 1 Strains in University of Vermont Selective Enrichments

2005 ◽  
Vol 71 (2) ◽  
pp. 961-967 ◽  
Author(s):  
Jesper Bartholin Bruhn ◽  
Birte Fonnesbech Vogel ◽  
Lone Gram
Keyword(s):  
Growth Rate ◽  
Listeria Monocytogenes ◽  
Brain Heart Infusion ◽  
Selective Medium ◽  
Individual Growth ◽  
Selective Enrichment ◽  
Enrichment Procedure ◽  
True Representation ◽  
Lineage 2 ◽  
University Of Vermont

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.

Delivery of Selective Agents via Time-Delayed Release Tablets Improves Recovery of Listeria monocytogenes Injured by Acid and Nitrite

2014 ◽  
Vol 77 (5) ◽  
pp. 772-780 ◽  
Author(s):  
ESMOND NYARKO ◽  
DENNIS D'AMICO ◽  
PATRICK MACH ◽  
WENSHENG XIA ◽  
CATHERINE DONNELLY
Keyword(s):  
Listeria Monocytogenes ◽  
Cell Populations ◽  
Enrichment Broth ◽  
Selective Enrichment ◽  
Delayed Release ◽  
Selective Agents ◽  
Meat Samples ◽  
Food Sample Analysis ◽  
University Of Vermont ◽  
The U.S

Listeria selective enrichment media are designed to enhance the isolation of the organism and increase the chances of detection. Drawbacks include the requirements for prolonged sample incubation (48 to 72 h) and manual addition of selective agents, which may be a source of contamination. Modified Listeria recovery broth (mLRB) is a proprietary enrichment medium formulated to facilitate the recovery of injured cells; its selective agents are incorporated into a format that allows delayed release until 6 h of incubation. We evaluated the change in cell populations over time for acid- and nitrite-injured Listeria monocytogenes in mLRB with the selective agents added manually at 0 h (mLRBS0) and 6 h (mLRBS6). Recovery of injured cells in mLRB plus time-delayed tablets (mLRBTD) was also compared with that in enrichment media recommended by the U.S. Department of Agriculture (University of Vermont broth), the U.S. Food and Drug Administration (buffered Listeria enrichment broth), and the International Organization for Standardization (demi-Fraser broth). Nitrite- or acid-injured Listeria at approximately 10 CFU/ml were inoculated into each broth medium, and Listeria populations were enumerated at various times from 12 to 48 h of incubation at 37°C. Analysis of variance revealed that acid-injured Listeria populations in mLRBS6 at 24 h were significantly higher (P < 0.05) than those in mLRBS0; however, the differences in populations on these two media were not significant for nitrite-injured cells. Cell populations of four strains of Listeria inoculated into mLRBTD were significantly higher at 24 h than when those strains were enriched in buffered Listeria enrichment broth, demi-Fraser broth, and University of Vermont broth. Comparison between artificially contaminated milk and meat samples with a four-strain cocktail of Listeria resulted in cell populations that were significantly higher (P < 0.05) at 24 h on mLRBTD for contaminated meat than on mLRB for contaminated milk. Delivery of selective agents via time-delayed release tablets into mLRB maximizes recovery of acid- and nitrite-injured Listeria and saves analyst time during food sample analysis.

Quantitative Evaluation of Three Selective Enrichment Broths and Agars Used in Recovering Listeria Microorganisms

1990 ◽  
Vol 53 (2) ◽  
pp. 105-110 ◽  
Author(s):  
JOSE FERNANDEZ-GARAYZABAL ◽  
CONSTANTIN GEMGEORGIS
Keyword(s):  
Brain Heart Infusion ◽  
Superior Performance ◽  
Enrichment Broth ◽  
Selective Enrichment ◽  
Naturally Occurring ◽  
Listeria Ivanovii ◽  
Soft Cheese ◽  
Meat Samples ◽  
Listeria Seeligeri ◽  
University Of Vermont

Three selective enrichment broths (FDA, University of Vermont and Dominguez Rodriguez) and lithium chloride-phenylethanol-moxolactam (LPM) agar, modified McBride (MMA) agar, Listeria selective agar (LSAM of Dominguez-Rodriguez), and Brain Heart Infusion (BHI) agar (as reference) were evaluated for their suitability to support the growth of six different species/strains of Listeria (Listeria monocytogenes Scott A, L. monocytogenes V7, L. monocytogenes VPH-1, Listeria innocua, Listeria seeligeri, and Listeria ivanovii). All Listeria strains grew faster and yielded a higher number of cells in FDA enrichment broth. Based on MPN studies, 1 to 2.1 cells of L. monocytogenes and L. innocua were needed for visible colony formation, on all three selective and BHI agars after 48 h incubation of 37°C. The LPM agar was more inhibitory for L. seeligeri and L. ivanovii requiring 9.6 and 917 cells, respectively, as compared to 1 to 2.7 cells for the other agars. The effectiveness of a particular combination among the selective enrichment broths and agars for recovering L. monocytogenes Scott A from inoculated cheese and meat samples was quantitated. Any enrichment broth combined with plating on LPM or LSAM agar gave 100% Listeria recovery as compared to 50 to 67% for plating on MMA agar. Both LPM and LSAM agars have also shown a superior performance to MMA agar in the recovery of naturally occurring Listeria from soft cheese and raw meat. The use of a secondary broth enrichment step improved the recovery of Listeria spp. from meat samples.

Molecular Characterization of Listeria monocytogenes in white meat samples from Punjab, India

2017 ◽  
Author(s):  
Simranpreet Kaur ◽  
Randhir Singh ◽  
Mandeep Kaur Sran ◽  
J.P. S. Gill
Keyword(s):  
Public Health ◽  
Listeria Monocytogenes ◽  
White Meat ◽  
Selective Enrichment ◽  
Retail Outlets ◽  
Meat Samples ◽  
Pcr Targeting ◽  
University Of Vermont

A study was undertaken to assess the prevalence of Listeria monocytogenes in white meats in the Punjab, India. A total of 335 samples including 115 samples of chicken, 75 samples of pork and 145 samples of fish were collected from retail outlets. Isolation of the pathogen was done by selective enrichment in University of Vermont Medium I and II and plating onto PALCAM agar. The recovered Listeria isolates were subjected to in-vitro pathogenicity assays and multiplex PCR targeting virulence-associated genes (prfA, plcA, actA, hlyA and iap) of L. monocytogenes. A total of thirty one (31) L. monocytogenes strains were isolated from meat samples with the prevalence of L. monocytogenes as 9.2%. Maximum prevalence was seen in fish (19.3%) followed by chicken (1.7%) and pork (1.3%). All isolates recovered from the study exhibited pathogenicity in in-vitro pathogenicity assays as well as possessed all the virulence related genes. Thus, the presence of pathogenic strains of L. monocytogenes in white meats with a prevalence of 9.2% appeared to be a cause for concern with profound public health implications.

Selective Enrichment Media Affect the Antibody-Based Detection of Stress-Exposed Listeria monocytogenes due to Differential Expression of Antibody-Reactive Antigens Identified by Protein Sequencing

2006 ◽  
Vol 69 (8) ◽  
pp. 1879-1886 ◽  
Author(s):  
TAO GENG ◽  
BYOUNG-KWON HAHM ◽  
ARUN K. BHUNIA
Keyword(s):  
Listeria Monocytogenes ◽  
Differential Expression ◽  
Brain Heart Infusion ◽  
Antigen Expression ◽  
Surface Proteins ◽  
Protein Sequencing ◽  
Enzyme Linked Immunosorbent Assay ◽  
Selective Enrichment ◽  
Elevated Expression ◽  
Detection Of Stress

Selective enrichment broths are frequently used to recover stressed Listeria cells to detectable levels, but the ability of antibodies to detect these cells from various commonly used enrichment media is unknown. In this study, a polyclonal (PAb) and monoclonal (MAb) antibody were used to examine the variation in antigen expression on healthy or stress-recovered Listeria monocytogenes cells grown in brain heart infusion broth, buffered Listeria enrichment broth (BLEB), Listeria repair broth (LRB), University of Vermont medium (UVM), and Fraser broth (FB) for immunodetection. Indirect enzyme-linked immunosorbent assay (ELISA) data showed that L. monocytogenes subjected to stresses (acid, cold, heat, and salt) and then grown in BLEB gave the highest reaction with the anti-Listeria PAb while those grown in LRB gave the highest reaction with the MAb C11E9. Cells grown in UVM and FB gave poor ELISA values with both antibodies. Western blotting with PAb revealed differential expression of surface proteins of 62, 58, 50, 43, and 30 kDa on L. monocytogenes cells, with most proteins displaying elevated expression in BLEB and LRB but reduced or no expression in UVM or FB. Similar differential expressions were noticed for C11E9. PAb-reactive proteins were identified as putative LPXTG-motif cell-wall anchor-domain protein (62 kDa; lmo0610), flavocytochrome C fumarate reductase chain A homolog protein (58 kDa; lmo0355), enolase (50 kDa; lmo2455), glyceraldehyde 3-phosphate dehydrogenase (43 kDa; lmo2459), and hypothetical phospho-sugar binding protein (30 kDa; lmo0041), respectively, and the MAb-reactive 66-kDa protein was confirmed to be N-acetylmuramidase (lmo2691). In conclusion, BLEB and LRB favorably supported increased expression of antigens and proved to be superior to UVM and FB for immunodetection of stressed L. monocytogenes cells.

Comparison of Procedures for Isolating Listeria monocytogenes in Soft, Surface-Ripened Cheese

1987 ◽  
Vol 50 (1) ◽  
pp. 4-6 ◽  
Author(s):  
MICHAEL P. DOYLE ◽  
JEAN L. SCHOENI
Keyword(s):  
Listeria Monocytogenes ◽  
Drug Administration ◽  
Food And Drug Administration ◽  
Cheese Sample ◽  
Selective Enrichment ◽  
Appl Environ ◽  
Enrichment Procedure ◽  
Soft Surface

Ninety samples of soft, surface-ripened cheese from a lot previously identified to contain Listeria were assayed for Listeria monocytogenes by three procedures. These included: (a) cold enrichment, (b) the Food and Drug Administration enrichment procedure, and (c) the selective enrichment procedure of Doyle and Schoeni (Appl. Environ. Microbiol. 15:1127, 1986). L. monocytogenes was isolated from 41 of the 90 cheese samples. The organism was isolated from only 9 of the 41 L. monocytogenes-positive samples by more than one procedure. Most isolations (21) were made by the cold enrichment procedure, with 16 and 13 isolations made by the FDA and Doyle-Schoeni procedures, respectively. In most instances, the organism was isolated from a cheese sample by only one procedure.

scholarly journals PSIX-18 Laurate and its glycerol monoester, monolaurin, as potential additives to control Listeria monocytogenes and tetracycline resistant Enterococcus faecalis in air-exposed silage

2020 ◽  
Vol 98 (Supplement_4) ◽  
pp. 414-415
Author(s):  
Yamicela Castillo-Castillo ◽  
Marina Ontiveros ◽  
Eric J Scholljegerdes ◽  
Robin Anderson ◽  
Claudio Arzola-Alvarez ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Enterococcus Faecalis ◽  
Brain Heart Infusion ◽  
Bactericidal Effect ◽  
Complete Elimination ◽  
Gram Positive Bacteria ◽  
Viable Cells ◽  
Colony Forming Units ◽  
Feed Value ◽  
Risk Infection

Abstract Silages can harbor pathogenic and antimicrobial resistant microbes which risk infection of food-producing animals. Livestock producers need effective yet environmentally friendly interventions to preserve the feed value of these fermented materials. Medium chain fatty acids such as laurate and its glycerol monoester, monolaurin, are potent inhibitors of many Gram-positive bacteria and when tested at 5 mg/mL in anaerobic cultures (n = 3/treatment) inoculated with 105 colony forming units (CFU) of Listeria monocytogenes and grown at 37oC in ½ strength Brain Heart infusion broth achieved near complete elimination of viable cells after 6 h compared to a 2.2 ± 0.1 log10 CFU/mL increase observed in controls. Culture of a tetracycline-resistant Enterococcus faecalis with 5 mg laurate/mL likewise achieved near complete elimination of viable cells (5 log10 CFU/mL) by 6 h incubation. The bactericidal effect of 5 mg monolaurin was less against E. faecalis, achieving a decrease of 1.8 ± 0.2 log10 CFU/mL and not decreased further after 24 h. When tested against air-exposed silage, pH 7.53 (4 g), mixed with 4 mL water, 5 mg laurate or monolaurin decreased viability of experimentally-inoculated L. monocytogenes (105 CFU/g silage) more (P < 0.05) than untreated controls after 24 h aerobic incubation (22oC), with viable counts being decreased 6.3 ± 0.1, 5.9 ± 0.8 and 4.5 ± 0.1 log10 CFU/g, respectively. In contrast, viable recovery of the experimentally-inoculated (105 CFU/g) tetracycline-resistant E. faecalis was reduced more (P < 0.05) than controls (decreased 0.7 ± 0.1 log10 CFU/g) after 6 h incubation when similarly tested with laurate and monolaurin (1.7 ± 0.5 and 3.0 ± 0.9 log10 CFU/g, respectively) but counts after 24 h were similar, decreasing on average 2.0 ± 0.5 log10 CFU/g). Results indicate laurate and monolaurin may be useful in killing L. monocytogenes and tetracycline-resistant E. faecalis during silage feed-out.

Ecophenotypic plasticity in shell growth direction of asari clam Ruditapes philippinarum

2021 ◽  
pp. 1-6
Author(s):  
Takeshi Tomiyama
Keyword(s):  
Growth Rate ◽  
Shell Growth ◽  
Shell Height ◽  
Growth Direction ◽  
Ruditapes Philippinarum ◽  
Shell Morphology ◽  
Individual Growth ◽  
Shell Size ◽  
Internal Factors ◽  
Suitable Habitats

Abstract Asari clam (or Manila clam) Ruditapes philippinarum is an important bivalve for local fisheries. This species exhibits a large variation in shell morphology, and the shell roundness tends to be greater in more unsuitable habitats. To test whether the increments in shell size parameters (length, height and width) were affected solely by environmental conditions or by internal factors such as initial shell shapes or growth rate, a field caging experiment was conducted at two different sites of unsuitable and suitable habitats in Matsukawaura Lagoon, Japan, where shell shapes of wild clams were significantly different between the habitats. In the experiment, clams were released from the two sites to the same site or to the other site and were re-collected after 3, 6 and 12 months of caging. Caged clams originating from unsuitable habitats and released to suitable habitats showed a reduction in shell height relative to shell length, while clams from suitable habitats introduced to unsuitable habitats showed marked increases in both shell height and width. Generalized linear mixed models suggested that the increase in shell height was affected largely by the release habitat (environment) whereas the increase in shell width was affected largely by the individual growth rate. These results suggest that marginal growths in shell height and width respond differently to external and internal factors of clams, resulting in plasticity in their shell shapes according to the environments to which they are translocated.

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