scholarly journals Resistance of Listeria monocytogenes biofilms to disinfectants 326

2010 ◽  
Vol 28 (No. 4) ◽  
pp. 326-332 ◽  
Author(s):  
S. Purkrtová ◽  
H. Turoňová ◽  
T. Pilchová ◽  
K. Demnerová ◽  
J. Pazlarová
Keyword(s):  
Listeria Monocytogenes ◽  
Reference Strain ◽  
Model Organism ◽  
Model System ◽  
Optimal Conditions ◽  
Microtiter Plates ◽  
Peptone Water ◽  
Optimal Values ◽  
Biofilm Development ◽  
Chloride Treatment

We studied the optimal conditions for the biofilm development by Listeria monocytogenes on a model system represented by microtiter plates, and also for determined some effective disinfectant agents. Listeria monocytogenes ATCC 13932 and an industrial isolate of Listeria monocytogenes Lm-24 were compared as to their abilities to form biofilms. The starting concentration of the cells leading to the most reproducible results was 0.5 McFarland. The temperatures tested ranged between 8°C to 37°C, the optimal values to form biofilm in buffered peptone water (BPW) with 0.05% glucose were 25°C and 30°C. Under comparable conditions the persistent strain L. monocytogenes Lm-24 constituted more massive biofilm than did the reference strain. The following disinfectants were applied: Savo, Merades Alco, benzalalkonium chloride. A persistent industry in isolate Listeria monocytogenes Lm-24 was used as the model organism for these tests. Benzalalkonium chloride treatment was found to be the most efficient way to damage the biofilm. One minute treatment with 500 mg/l was lethal for the biofilm cells, and that with 125 mg/l for planctonic cells. Savo suppresed the viability of the biofilm cells only by about 20% on average while being lethal for planctonic cells. Merades Alco exhibited only a weak effect on both the biofilm and planctonic cells.

scholarly journals Design of an Experimental Viscoelastic Food Model System for Studying Zygosaccharomyces bailii Spoilage in Acidic Sauces

2009 ◽  
Vol 75 (22) ◽  
pp. 7060-7069 ◽  
Author(s):  
L. Mertens ◽  
A. H. Geeraerd ◽  
T. D. T. Dang ◽  
A. Vermeulen ◽  
K. Serneels ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Viscoelastic Behavior ◽  
Model System ◽  
Gelling Agent ◽  
Glycerol Concentration ◽  
Zygosaccharomyces Bailii ◽  
Microtiter Plates ◽  
Absorbance Detection ◽  
Food Structure ◽  
Food Model

ABSTRACT Within the field of predictive microbiology, the number of studies that quantify the effect of food structure on microbial behavior is very limited. This is mainly due to impracticalities related to the use of a nonliquid growth medium. In this study, an experimental food model system for studying yeast spoilage in acid sauces was developed by selecting a suitable thickening/gelling agent. In a first step, a variety of thickening/gelling agents was screened, with respect to the main physicochemical (pH, water activity, and acetic acid and sugar concentrations) and rheological (weak gel viscoelastic behavior and presence of a yield stress) characteristics of acid sauces. Second, the rheological behavior of the selected thickening/gelling agent, Carbopol 980, was extensively studied within the following range of conditions: pH 4.0 to 5.0, acetic acid concentration of 0 to 1.0% (vol/vol), glycerol concentration of 0 to 15% (wt/vol), and Carbopol concentration of 1.0 to 1.5% (wt/vol). Finally, the applicability of the model system was illustrated by performing growth experiments in microtiter plates for Zygosaccharomyces bailii at 0, 0.5, 1.0, and 1.5% (wt/vol) Carbopol, 5% (wt/vol) glycerol, 0% (vol/vol) acetic acid, and pH 5.0. A shift from planktonic growth to growth in colonies was observed when the Carbopol concentration increased from 0.5 to 1.0%. The applicability of the model system was illustrated by estimating μmax at 0.5% Carbopol from absorbance detection times.

Influence of partial inactivation on growth of Listeria monocytogenes under sub-optimal conditions of increased NaCl concentration or increased acidity

2009 ◽  
Vol 10 (2) ◽  
pp. 267-271 ◽  
Author(s):  
Andreja Rajkovic ◽  
Mieke Uyttendaele ◽  
Nancy Van Houteghem ◽  
Sandra Maria Osés Gómez ◽  
Johan Debevere ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Optimal Conditions ◽  
Nacl Concentration ◽  
Partial Inactivation

Listeria monocytogenes: silage, sandwiches and science

2005 ◽  
Vol 6 (2) ◽  
pp. 211-217 ◽  
Author(s):  
Charles J. Czuprynski
Keyword(s):  
Listeria Monocytogenes ◽  
Murine Model ◽  
Pathogenic Bacteria ◽  
Model Organism ◽  
Intracellular Pathogen ◽  
Innate And Adaptive Immunity ◽  
Potential Vector ◽  
Broad Array ◽  
Common Framework ◽  
Substantial Risk

AbstractListeria monocytogenesis amongst the most intriguing and well studied of the pathogenic bacteria. However, the understanding and perspective one has ofL. monocytogenesdepends to a large extent on the microbiological issues with which one is faced as a part of your professional duties. The focus of the veterinary clinician or investigator is likely to be foremost on the neurologic (circling disease) and reproductive diseasesL. monocytogenescauses. To the food microbiologist, the principal concern is to prevent introduction ofL. monocytogenesinto food products, or to identify its presence and prevent its multiplication to numbers of organisms that are likely to pose a substantial risk to humans who ingest the product. To the cellular immunologist, listeriosis represents a robust murine model that helped to elucidate many important concepts in innate and adaptive immunity, andL. monocytogenesis a potential vector for delivery of novel vaccines. To the student of molecular pathogenesis,L. monocytogenesis a powerful and well-characterized model organism for studying the cellular microbiology of an intracellular pathogen. In this brief overview, I will attempt to highlight some of the classical observations, and contemporary insights, onL. monocytogenesand listeriosis, and integrate these perspectives into a common framework. By so doing, I hope to provide those with one perspective on listeriosis with an appreciation of the broad array of problems and issues faced by those who focus on some other aspect ofL. monocytogenesand its pathogenesis.

Gene Transcription Patterns of pH- and Salt-Stressed Listeria monocytogenes Cells in Simulated Gastric and Pancreatic Conditions

2014 ◽  
Vol 77 (2) ◽  
pp. 254-261 ◽  
Author(s):  
MARIOS MATARAGAS ◽  
ANNA GREPPI ◽  
KALLIOPI RANTSIOU ◽  
LUCA COCOLIN
Keyword(s):  
Life Cycle ◽  
Listeria Monocytogenes ◽  
Reference Strain ◽  
Expression Patterns ◽  
Wild Strain ◽  
Hostile Environment ◽  
Fermented Sausage ◽  
Laboratory Reference ◽  
Serotype 1 ◽  
Serotype 4B

A Listeria monocytogenes subgenomic array, targeting 54 genes involved in the adhesion, adaptation, intracellular life cycle, invasion, and regulation of the infection cycle was used to investigate the gene expression patterns of acid- and salt-stressed Listeria cells after exposure to conditions similar to those in gastric and pancreatic fluids. Three L. monocytogenes strains, one laboratory reference strain (EGDe) and two food isolates (wild strain 12 isolated from milk and wild strain 3 isolated from fermented sausage), were used during the studies. Differences in the expressed genes were observed between the gastric and pancreatic treatments and also between the serotypes. Increased transcripts were observed of the genes belonging to the adaptation and regulation group for serotype 4b (strain 12) and to the invasion and regulation group for serotype 1/2a (strain EGDe). Interestingly, no significantly differentially expressed genes were found for serotype 3c (strain 3) in most cases. The genes related to adaptation (serotype 1/2a) and to intracellular life cycle and invasion (serotype 4b) were down-regulated in order to cope with the hostile environment of the gastric and pancreatic fluids. These findings may provide experimental evidence for the dominance of serotypes 1/2a and 4b in clinical cases of listeriosis and for the sporadic occurrence of serotype 3c.

scholarly journals An Effective Counterselection System for Listeria monocytogenes and Its Use To Characterize the Monocin Genomic Region of Strain 10403S

2016 ◽  
Vol 83 (6) ◽  
Author(s):  
Tal Argov ◽  
Lev Rabinovich ◽  
Nadejda Sigal ◽  
Anat A. Herskovits
Keyword(s):  
Listeria Monocytogenes ◽  
Point Mutations ◽  
Model Organism ◽  
Trna Synthetase ◽  
Genomic Region ◽  
Selection Marker ◽  
Content Type ◽  
Allelic Exchange ◽  
Suicide Vector ◽  
Screening Systems

ABSTRACT Construction of Listeria monocytogenes mutants by allelic exchange has been laborious and time-consuming due to lack of proficient selection markers for the final recombination event, that is, a marker conveying substance sensitivity to the bacteria bearing it, enabling the exclusion of merodiploids and selection for plasmid loss. In order to address this issue, we engineered a counterselection marker based on a mutated phenylalanyl-tRNA synthetase gene (pheS*). This mutation renders the phenylalanine-binding site of the enzyme more promiscuous and allows the binding of the toxic p-chloro-phenylalanine analog (p-Cl-phe) as a substrate. When pheS* is introduced into L. monocytogenes and highly expressed under control of a constitutively active promoter, the bacteria become sensitive to p-Cl-phe supplemented in the medium. This enabled us to utilize pheS* as a negative selection marker and generate a novel, efficient suicide vector for allelic exchange in L. monocytogenes. We used this vector to investigate the monocin genomic region in L. monocytogenes strain 10403S by constructing deletion mutants of the region. We have found this region to be active and to cause bacterial lysis upon mitomycin C treatment. The future applications of such an effective counterselection system, which does not require any background genomic alterations, are vast, as it can be modularly used in various selection systems (e.g., genetic screens). We expect this counterselection marker to be a valuable genetic tool in research on L. monocytogenes. IMPORTANCE L. monocytogenes is an opportunistic intracellular pathogen and a widely studied model organism. An efficient counterselection marker is a long-standing need in Listeria research for improving the ability to design and perform various genetic manipulations and screening systems for different purposes. We report the construction and utilization of an efficient suicide vector for allelic exchange which can be conjugated, leaves no marker in the bacterial chromosome, and does not require the use of sometimes leaky inducible promoters. This highly efficient genome editing tool for L. monocytogenes will allow for rapid sequential mutagenesis, introduction of point mutations, and design of screening systems. We anticipate that it will be extensively used by the research community and yield novel insights into the diverse fields studied using this model organism.

scholarly journals Ultrasonic Cleaning of Conveyor Belt Materials Using Listeria monocytogenes as a Model Organism

2007 ◽  
Vol 70 (3) ◽  
pp. 758-761 ◽  
Author(s):  
RIINA TOLVANEN ◽  
JANNE LUNDÉN ◽  
HANNU KORKEALA ◽  
GUN WIRTANEN
Keyword(s):  
Stainless Steel ◽  
Listeria Monocytogenes ◽  
Model Organism ◽  
Conveyor Belt ◽  
Difficult Problem ◽  
Cleaning Efficiency ◽  
Ultrasonic Cleaning ◽  
Plastic Materials ◽  
Significant Difference ◽  
Logarithmic Reduction

Persistent Listeria monocytogenes contamination of food industry equipment is a difficult problem to solve. Ultrasonic cleaning offers new possibilities for cleaning conveyors and other equipment that are not easy to clean. Ultrasonic cleaning was tested on three conveyor belt materials: polypropylene, acetal, and stainless steel (cold-rolled, AISI 304). Cleaning efficiency was tested at two temperatures (30 and 45°C) and two cleaning times (30 and 60 s) with two cleaning detergents (KOH, and NaOH combined with KOH). Conveyor belt materials were soiled with milk-based soil and L. monocytogenes strains V1, V3, and B9, and then incubated for 72 h to attach bacteria to surfaces. Ultrasonic cleaning treatments reduced L. monocytogenes counts on stainless steel 4.61 to 5.90 log units; on acetal, 3.37 to 5.55 log units; and on polypropylene, 2.31 to 4.40 log units. The logarithmic reduction differences were statistically analyzed by analysis of variance using Statistical Package for the Social Sciences software. The logarithmic reduction was significantly greater in stainless steel than in plastic materials (P < 0.001 for polypropylene, P = 0.023 for acetal). Higher temperatures enhanced the cleaning efficiency in tested materials. No significant difference occurred between cleaning times. The logarithmic reduction was significantly higher (P = 0.013) in cleaning treatments with potassium hydroxide detergent. In this study, ultrasonic cleaning was efficient for cleaning conveyor belt materials.

scholarly journals Establishment of Neurospora crassa as a model organism for fungal virology

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Shinji Honda ◽  
Ana Eusebio-Cope ◽  
Shuhei Miyashita ◽  
Ayumi Yokoyama ◽  
Annisa Aulia ◽  
...  
Keyword(s):  
Viral Replication ◽  
Neurospora Crassa ◽  
Rna Viruses ◽  
Model Organism ◽  
Model System ◽  
Double Stranded Rna ◽  
Antiviral Responses ◽  
Positive Sense ◽  
Host Virus Interactions ◽  
Virus Interactions

Abstract The filamentous fungus Neurospora crassa is used as a model organism for genetics, developmental biology and molecular biology. Remarkably, it is not known to host or to be susceptible to infection with any viruses. Here, we identify diverse RNA viruses in N. crassa and other Neurospora species, and show that N. crassa supports the replication of these viruses as well as some viruses from other fungi. Several encapsidated double-stranded RNA viruses and capsid-less positive-sense single-stranded RNA viruses can be experimentally introduced into N. crassa protoplasts or spheroplasts. This allowed us to examine viral replication and RNAi-mediated antiviral responses in this organism. We show that viral infection upregulates the transcription of RNAi components, and that Dicer proteins (DCL-1, DCL-2) and an Argonaute (QDE-2) participate in suppression of viral replication. Our study thus establishes N. crassa as a model system for the study of host-virus interactions.

scholarly journals Rosmarinic Acid Interaction with Planktonic and Biofilm Staphylococcus aureus

2013 ◽  
Vol 8 (12) ◽  
pp. 1934578X1300801 ◽  
Author(s):  
Lívia Slobodníková ◽  
Silvia Fialová ◽  
Helena Hupková ◽  
Daniel Grančai
Keyword(s):  
Staphylococcus Aureus ◽  
Rosmarinic Acid ◽  
Antibacterial Activities ◽  
Microtiter Plate ◽  
Dependent Manner ◽  
Early Stages ◽  
Microtiter Plates ◽  
Sole Agent ◽  
The Subject ◽  
Biofilm Development

The subject of study was the evaluation of antibacterial activities of rosmarinic acid (RA) on clinical Staphylococcus aureus strains obtained from catheter-related infections. Minimal inhibitory (MIC) and minimal bactericidal concentrations (MBC) of RA were tested by broth microdilution assay. Biofilm-eradication activity was detected on 24-hour biofilm in microtiter plates using a regrowth technique; activity on biofilm formation was measured by a microtiter plate method after RA application to bacterial samples after 0, 1, 3 and 6 hours of biofilm development. RA had antimicrobial activity on all tested strains in concentrations from 625 to 1250 μg.mL−1 (MICs equal to MBCs). No biofilm-eradication activity on 24-hour biofilm was observed in the tested range of concentrations (from 156 to 5000 μg.mL−1). Subinhibitory RA concentrations suppressed the biofilm production, when applied at early stages of its development. Concentrations lower than subinhibitory stimulated the biofilm mass production in a concentration- and time-dependent manner. Considering our results, RA could be a candidate for a topical antimicrobial agent with killing activity on planktonic forms of bacteria and suppressing activity in the early stages of biofilm development, but probably not for the therapy of catheter-related infections as a sole agent.

Evaluation of Nisin-Coated Cellulose Casings for the Control of Listeria monocytogenes Inoculated onto the Surface of Commercially Prepared Frankfurters†‡

2004 ◽  
Vol 67 (5) ◽  
pp. 1017-1021 ◽  
Author(s):  
JOHN B. LUCHANSKY ◽  
JEFFREY E. CALL
Keyword(s):  
Listeria Monocytogenes ◽  
Surface Area ◽  
Internal Surface ◽  
Refrigerated Storage ◽  
Internal Surface Area ◽  
Appreciable Increase ◽  
Potassium Lactate ◽  
Selective Agar ◽  
Peptone Water ◽  
Sodium Diacetate

Commercially prepared frankfurters were formulated with and without ~1.4% potassium lactate and 0.1% sodium diacetate and were subsequently processed in cellulose casings coated with and without nisin (~50,000 IU per square inch of internal surface area) to control the outgrowth of Listeria monocytogenes during refrigerated storage. The frankfurters were inoculated with ~5 log CFU per package of a five-strain mixture of L. monocytogenes and then vacuum sealed before being stored at 4° C for 60 to 90 days. Surviving organisms were recovered and enumerated by rinsing each package with 18 ml of sterile 0.1% peptone water and plating onto MOX selective agar. The data for each of two trials were averaged. In packages that contained frankfurters formulated with potassium lactate and sodium diacetate and prepared in nisin-coated casings, L. monocytogenes levels decreased by 1.15 log CFU per package after 90 days of storage. L. monocytogenes levels decreased by 0.95 log CFU per package in frankfurters that were prepared in casings that were not coated with nisin. In packages of frankfurters that were formulated without potassium lactate and sodium diacetate and prepared in nisin-coated casings, L. monocytogenes levels decreased by 0.88 log CFU per package after 15 days of storage but then increased appreciablythereafter over a 60-day period of refrigerated storage. There was also an appreciable increase in pathogen numbers during 60 days of storage in otherwise similar frankfurters formulated without potassium lactate and sodium diacetate prepared in casings that were not coated with nisin. These data confirm that potassium lactate and sodium diacetate display listeriostatic activity as an ingredient of commercial frankfurters. These data also establish that cellulose casings coated with nisin display only moderate antilisterial activity in vacuum-sealed packages of commercially prepared frankfurters during storage at 4° C.

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