scholarly journals Identifying Suitable Listeria innocua Strains as Surrogates for Listeria monocytogenes for Horticultural Products

2019 ◽  
Vol 10 ◽  
Author(s):  
Vathsala Mohan ◽  
Reginald Wibisono ◽  
Lana de Hoop ◽  
Graeme Summers ◽  
Graham C. Fletcher
Keyword(s):  
Listeria Monocytogenes ◽  
Listeria Innocua ◽  
Horticultural Products

scholarly journals Identifying suitableListeria innocuastrains as surrogates forListeria monocytogenesfor horticultural products

2019 ◽  
Author(s):  
Vathsala Mohan ◽  
Reginald Wibisono ◽  
Lana de Hoop ◽  
Graeme Summers ◽  
Graham C Fletcher
Keyword(s):  
Listeria Monocytogenes ◽  
Thermal Inactivation ◽  
Listeria Innocua ◽  
Peroxyacetic Acid ◽  
Safety Risks ◽  
Horticultural Products ◽  
Different Strains ◽  
The Individual ◽  
Uv C ◽  
Strain Dependent

AbstractWe conducted a laboratory-based study testing nineListeria innocuastrains independently and a cocktail of 11Listeria monocytogenesstrains. The aim was to identify suitableL. innocuastrain(s) to modelL. monocytogenesin inactivation experiments. Three separate inactivation procedures and a hurdle combination of the three were employed: thermal inactivation (55°C), UV-C irradiation (245 nm) and chemical sanitiser (Tsunami™ 100, a mixture of acetic acid, peroxyacetic acid and hydrogen peroxide). The responses were strain dependent in the case ofL. innocuawith different strains responding differently to different regimes.L. innocuaisolates generally responded differently to theL. monocytogenescocktail and had different responses among themselves. In the thermal inactivation treatment, inactivation of all strains including theL. monocytogenescocktail plateaued after 120 minutes. Chemical sanitiser, inactivation could be achieved at concentrations of 10 and 20 ppm with inactivation increasing with contact time up to 8 minutes, beyond which there was no significant benefit. Although most of theL. innocuastrains in the study responded similarly toL. monocytogeneswhen subjected to a single inactivation treatment, when the treatments were applied as hurdle, allL. innocuastrains except PFR16D08 were more sensitive than theL. monocytogenescocktail. PFR16D08 almost matched the resistance of theL. monocytogenescocktail but was much more resistant to the individual treaments. A cocktail of twoL. innocuastrains (PFR 05A07 and PFR 05A10) had the closest responses to the hurdle treatment to those of theL. monocytogenescocktail and is therefore recommended for hurdle experiments.ImportanceOwing to researcher safety risks it is often difficult to use actual pathogens, such asListeria monocytogenes, to explore different inactivation procedures under field conditions. Organisms that are closely related to the pathogen but without its virulence are therefore used as surrogates for the actual pathogen. However, this assumes that the surrogate will behave in a similar manner to the pathogen and it is difficult to predict the responses of the surrogate compared to the actual pathogen. This study compares the responses of individual and combined “cocktails” of strains of non-pathogenicListeria innocuato different inactivation procedures when compared to the response of a cocktail ofL. monocytogenes. Our study highlights the importance of evaluating a number of strains when choosing surrogates.

scholarly journals Thermal inactivation and growth potential of Listeria monocytogenes in smoked tench

2016 ◽  
Vol 5 (3) ◽  
Author(s):  
Raffaella Branciari ◽  
Andrea Valiani ◽  
Raffaella Franceschini ◽  
David Ranucci ◽  
Alessia Lupattelli ◽  
...  
Keyword(s):  
Experimental Study ◽  
Listeria Monocytogenes ◽  
Thermal Inactivation ◽  
Challenge Test ◽  
Listeria Innocua ◽  
Growth Potential ◽  
Post Processing ◽  
Colony Forming Unit ◽  
Post Process ◽  
Hygiene Measures

An experimental study for the evaluation of <em>Listeria monocytogenes</em> inactivation during a hot smoking process in tench was performed using <em>Listeria innocua</em> strains. Furthermore, the survival of <em>L. monocytogenes</em> in smoked tench was determined after post-processing in contaminated samples, evaluating the growth potential during storage. <em>L. innocua</em> was not detected after the smoking process. In the challenge test, the growth potential of <em>L. monocytogenes</em> was 5.68 log colony forming unit g<sup>−1</sup>. The results showed that hot smoking at an inner temperature around 72°C is able to eliminate the microorganism. Nevertheless, the product is able to support the growth of the pathogen if post-process contamination occurs, as the food is suitable for <em>Listeria</em> multiplication. Product recontamination should be prevented by means of appropriate application of hygiene measures.

scholarly journals Antibacterial activity of plant extracts against Listeria monocytogenes isolated from ready-to-eat salads

2020 ◽  
Vol 13 (1) ◽  
pp. 131-143
Author(s):  
É. György ◽  
É. Laslo ◽  
E. Csató
Keyword(s):  
Listeria Monocytogenes ◽  
Essential Oils ◽  
Antibacterial Effect ◽  
Storage Conditions ◽  
Inhibitory Effect ◽  
Listeria Innocua ◽  
Foodborne Diseases ◽  
Bacterial Strains ◽  
Antibacterial Effects ◽  
Growth Environment

Abstract Ready-to-eat salads are becoming more and more popular. However, due to their ingredients, they represent a suitable growth environment for different microbes. In the prevention of foodborne diseases, hygienic food preparation and appropriate storage conditions are very important. During this study, ten different ready-to-eat salads were analysed for the presence of Listeria monocytogenes. Five different selective agar mediums were used for the enumeration and isolation of Listeria monocytogenes. The isolated bacterial strains were subjected to morphological and biochemical confirmation tests. The antibacterial effects of five different freshly squeezed vegetable juices (carrots, celery, beets, horseradish, and onions) and of five essential oils (dill, thyme, oregano, lemongrass, and sage) were determined against Listeria monocytogenes, Listeria innocua, and L. monocytogenes strains isolated from ready-to-eat salads. Based on the results obtained from fresh vegetable juices, carrot juice exerted the highest antibacterial effect, while the others showed no or slight inhibitory effect (horseradish, beets, onions) against Listeria species. Among the essential oils, thyme, lemongrass, and oregano showed the strongest antibacterial effect against the studied Listeria species.

Occurrence of Listeria monocytogenes in Milk and Dairy Products Produced or Imported Into Morocco

1993 ◽  
Vol 56 (3) ◽  
pp. 256-259 ◽  
Author(s):  
A. EL MARRAKCHI ◽  
A. HAMAMA ◽  
F. EL OTHMANI
Keyword(s):  
Listeria Monocytogenes ◽  
Dairy Products ◽  
Raw Milk ◽  
Listeria Innocua ◽  
Pasteurized Milk ◽  
Listeria Species ◽  
Fresh Cheese ◽  
Milk And Dairy Products

Examination of 227 samples of milk and dairy products for Listeria monocytogenes showed that raw milk and some Moroccan traditionally made dairy products such as Iben and raib (fermented milks) and jben (fresh cheese) were contaminated with this pathogen. L. monocytogenes was the only Listeria species isolated except in one case in which it was associated with Listeria innocua. Pasteurized milk, fresh cream, and fresh and ripened cheeses (industrially made) were free from L. monocytogenes.

Some Chemical and Bacteriological Characteristics of Regional Cheeses from Asturias, Spain

1996 ◽  
Vol 59 (5) ◽  
pp. 509-515 ◽  
Author(s):  
ABELARDO MARGOLLES ◽  
ANA RODRIGUEZ ◽  
CLARA G. de los REYES-GAVILAN
Keyword(s):  
Listeria Monocytogenes ◽  
Listeria Innocua ◽  
Chemical Characteristics ◽  
Salmonella Spp ◽  
Cheese Making ◽  
Ph Values ◽  
Plate Counts ◽  
Coagulase Positive Staphylococci ◽  
Enrichment Methods

One hundred and one samples of six representative short-ripened cheeses (five homemade and one industrially manufactured) were collected over 1 year in several supermarkets in Asturias and analyzed for mesophilic plate counts, coliforms, enterobacteria, coagulase-positive staphylococci, the presence of species of Salmonella and Listeria, pH, moisture, NaCl, and aw. Chemical characteristics varied, largely depending on the type of cheese. The percentages of moisture and NaCl ranged from 36.11 to 48.91 and from 1.16 to 2.08 respectively. The aw values were between 0.95 and 0.99. Acidification was quite efficient, all cheeses having mean pH values between 4.56 and 5.39. None of the samples yielded Salmonella spp. Coagulase-positive staphylococci were detected in two cheeses, in one reaching levels up to 106 CFU/g. Listeria spp. contaminated 11.8% of the cheeses, with Listeria monocytogenes isolated from 8.91 % and Listeria innocua from 4.95% of the samples. The distribution of Listeria spp. varied largely depending on the type of cheese: 41% of the samples contaminated with L. monocytogeneswere obtained from one type of cheese which had the lowest pH and NaCl values and the highest aw and moisture levels of the cheeses analyzed. However, L. monocytogenes was absent from another type of cheese, which showed intermediate chemical characteristics. High levels of coliforms and enterobacteria (4 to 5 log CFU/ml) were detected in the five homemade cheeses and were statistically associated with the presence of Listeria spp. and L. monocytogenes. Cold enrichment was unsuccessful for the recovery of Listeria spp. from the cheeses analyzed, while a combination of different enrichment methods resulted in the best procedure for detecting all positive samples. This study shows that L. monocytogenes and coagulase-positive staphylococci are present in short-ripened cheeses consumed in Asturias. Adequate measures to prevent contamination during cheese making will probably result in safer products.

Incidence of Listeria monocytogenes in Silage and Its Subsequent Control by Specific and Nonspecific Antagonism

1990 ◽  
Vol 53 (8) ◽  
pp. 642-647 ◽  
Author(s):  
CURTT M. PERRY ◽  
CATHERINE W. DONNELLY
Keyword(s):  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Lactic Acid Bacteria ◽  
Acid Production ◽  
Lactic Acid Production ◽  
Dairy Farms ◽  
Listeria Innocua ◽  
Listeria Species

Silage samples representing approximately 10% of Vermont's dairy farms were tested for the presence of Listeria species. Listeria innocua was isolated from 15.3% of the silage samples, while Listeria monocytogenes was isolated from 2.9% of the examined samples. As silage pH increased, the incidence of Listeria increased concomitantly. Seventy-eight mesophilic lactic acid bacteria, indigenous to silage, were screened for specific and nonspecific antagonism against four L. monocytogenes indicator strains. Most of the silage isolates demonstrated nonspecific inhibition via lactic acid production against the L. monocytogenes indicator strains. None of the indigenous silage isolates tested in this survey demonstrated specific antagonism via production of bacteriocinogenic compounds.

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