scholarly journals Development of a repair-enrichment broth for resuscitation of heat-injured Listeria monocytogenes and Listeria innocua.

1992 ◽  
Vol 58 (1) ◽  
pp. 14-20 ◽  
Author(s):  
S V Busch ◽  
C W Donnelly
Keyword(s):  
Listeria Monocytogenes ◽  
Listeria Innocua ◽  
Enrichment Broth

Detection of Listeria monocytogenes in Samples Containing Listeria innocua

1994 ◽  
Vol 57 (12) ◽  
pp. 1048-1051 ◽  
Author(s):  
MICHAEL S. CURIALE ◽  
CATHERINE LEWUS
Keyword(s):  
Listeria Monocytogenes ◽  
Growth Rates ◽  
Environmental Samples ◽  
Listeria Innocua ◽  
Enrichment Broth ◽  
Selective Media ◽  
Common Culture ◽  
Generation Times ◽  
Secondary Enrichment ◽  
Culture Procedure

A common culture procedure for the detection of Listeria monocytogenes in meats and environmental samples was evaluated in a multilaboratory study using samples inoculated with both Listeria monocytogenes and Listeria innocua. Listeria monocytogenes was recovered from 5.4% of beef broth samples containing between 140 and 1400 L. monocytogenes cells per 25-ml sample in the presence of twice as many L. innocua cells; whereas L. innocua was recovered from all of the samples. Listeria monocytogenes was isolated from 100% of the samples when L. innocua was absent. Similar results were obtained for swab samples containing both L. monocytogenes and L. innocua. Listeria monocytogenes was recovered from 31% of the swabs containing 4.8 L. monocytogenes cells per swab and from 0% of the swabs containing the same number of L. monocytogenes cells and 4 L. innocua cells per swab. When the ratios of L. monocytogenes to L. innocua were 12:1, 120:1 and 1200:1, L. monocytogenes was isolated from 38%, 92% and 85% of the swabs, respectively. The recovery rates were consistent with the differences in growth rates for the two organisms in selective media. The generation times for L. monocytogenes were 74 min in primary enrichment broth and 105 min in modified secondary enrichment broth. Listeria innocua posted generation times of 53 and 81 min in the same two enrichment broths.

Simultaneous Growth of Listeria monocytogenes and Listeria innocua

1993 ◽  
Vol 56 (7) ◽  
pp. 616-618 ◽  
Author(s):  
RUTH L. PETRAN ◽  
KATHERINE M. J. SWANSON
Keyword(s):  
Listeria Monocytogenes ◽  
Yeast Extract ◽  
Environmental Samples ◽  
Culture Media ◽  
Listeria Innocua ◽  
Enrichment Broth ◽  
University Of Vermont ◽  
Simultaneous Growth

Listeria spp. have been isolated from a wide variety of sources, and in many situations Listeria innocua is more commonly found than Listeria monocytogenes. Growth of three L. monocytogenes strains was studied when inoculated simultaneously with a rhamnose negative L. innocua strain into culture media and cheese sauce. Fraser broth (FB), Trypticase™ soy broth plus 0.6% yeast extract (TSB-YE), University of Vermont medium (UVM) modified Listeria enrichment broth, and cheese sauce were inoculated (ca. 102 cells per ml) and incubated for 24 h; FB, TSB-YE, and cheese sauce at 35°C, UVM at 30°C. Growth of four rhamnose-positive, L. innocua strains was also studied in culture media. Growth of L. monocytogenes was similar to that for L. innocua in TSB-YE or cheese sauce. However, in FB and UVM, L. innocua populations were significantly higher than L. monocytogenes. This occurred when media were inoculated individually or simultaneously. This may explain in part why L. innocua is isolated more frequently than L. monocytogenes from foods and environmental samples.

Development of a Novel Listeria Enrichment Broth for the Isolation of Pathogenic Listeria

2017 ◽  
Vol 80 (10) ◽  
pp. 1768-1776 ◽  
Author(s):  
Dongxin Liu ◽  
Yan Wang ◽  
Yi Wang ◽  
Lu Zhang ◽  
Lijuan Luo ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Listeria Innocua ◽  
International Organization ◽  
The Novel ◽  
Isolation Rate ◽  
Enrichment Broth ◽  
Aerobic Conditions ◽  
Enrichment Medium ◽  
Listeria Ivanovii ◽  
Secondary Enrichment

ABSTRACT Listeriosis, the disease caused by pathogenic Listeria species, can present severe symptoms in susceptible people. The goal of this study was to develop a novel enrichment broth, Listeria allose enrichment broth (LAEB), to improve isolation of Listeria monocytogenes and Listeria ivanovii from samples through incorporating a specific carbohydrate and reducing inhibitor concentrations. Other coexisting bacteria, particularly Listeria innocua, can interfere with the isolation of pathogenic Listeria in such ways as overgrowth of L. innocua and the generation of inhibitory metabolites. The incorporation of allose into the novel LAEB was effective for slowing the growth of L. innocua and other nontarget microorganisms. We determined that 35°C and pH 7.0 under aerobic conditions are optimal for Listeria growth in this medium. The novelty of the use of LAEB is the single enrichment procedure at 35°C for 24 h, obviating the need for a secondary enrichment medium. In 50 simulated samples, the sensitivity of the LAEB method (86%) was higher than that of the International Organization for Standardization (EN ISO) method (70%). In 142 naturally contaminated samples tested, the isolation rate for pathogenic Listeria with the LAEB method was 26.0% (37 of 142 samples), which was significantly higher than the 17.6% (25 of 142 samples) for the EN ISO method. Higher isolation rates and a quicker and easier protocol make the novel LAEB method an appropriate alternative for the isolation of pathogenic Listeria.

scholarly journals Postenrichment Population Differentials Using Buffered Listeria Enrichment Broth: Implications of the Presence of Listeria innocua on Listeria monocytogenes in Food Test Samples†

2013 ◽  
Vol 76 (11) ◽  
pp. 1854-1862 ◽  
Author(s):  
ASHLEY L. KEYS ◽  
RACHEL C. DAILEY ◽  
ANTHONY D. HITCHINS ◽  
R. DERIKE SMILEY
Keyword(s):  
Growth Rate ◽  
Listeria Monocytogenes ◽  
Listeria Innocua ◽  
Population Differences ◽  
Enrichment Broth ◽  
Listeria Species ◽  
Plating Method ◽  
Low Levels ◽  
Pathogen Recovery ◽  
Enrichment Step

The recovery of low levels of Listeria monocytogenes from foods is complicated by the presence of competing microorganisms. Nonpathogenic species of Listeria pose a particular problem because variation in growth rate during the enrichment step can produce more colonies of these nontarget cells on selective and/or differential media, resulting in a preferential recovery of nonpathogens, especially Listeria innocua. To gauge the extent of this statistical barrier to pathogen recovery, 10 isolates each of L. monocytogenes and L. innocua were propagated together from approximately equal initial levels using the current U.S. Food and Drug Administration's enrichment procedure. In the 100 isolate pairs, an average 1.3-log decrease was found in the 48-h enrichment L. monocytogenes population when L. innocua was present. In 98 of the 100 isolate pairs, L. innocua reached higher levels at 48 h than did L. monocytogenes, with a difference of 0.2 to 2.4 log CFU/ml. The significance of these population differences was apparent by an increase in the difficulty of isolating L. monocytogenes by the streak plating method. L. monocytogenes went completely undetected in 18 of 30 enrichment cultures even after colony isolation was attempted on Oxoid chromogenic Listeria agar. This finding suggests that although both Listeria species were present on the plate, the population differential between them restricted L. monocytogenes to areas of the plate with confluent growth and that isolated individual colonies were only L. innocua.

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.

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