Assessment of different selective agar media for enumeration and isolation ofListeriafrom dairy products

1988 ◽  
Vol 55 (4) ◽  
pp. 579-583 ◽  
Author(s):  
Lucas Dominguez ◽  
José Francisco Fernández ◽  
Victor Briones ◽  
José Luis Blanco ◽  
Guillermo Suárez
Keyword(s):  
Dairy Products ◽  
Agar Medium ◽  
Raw Milk ◽  
Superior Performance ◽  
Direct Plating ◽  
Selective Agar ◽  
Natural Microflora ◽  
Agar Media ◽  
The Difference ◽  
Better Than

SummaryDifferent selective agar media were compared for the recovery and isolation of five species ofListeriafrom raw milk and cheese. The selective media examined were Beerens medium, MacBride medium and that described by Dominguezet al.(1984) with 6 mg/1 acriflavine, listeria selective agar medium (LSAM), and LSAM with 12 mg/1 acriflavine (LSAM × 2A); a non-selective yeast glucose Lemco agar was included for comparison. When the difference between listeria and the natural microflora of raw milk and cheese was 102cfu/ml, listeria could be isolated by direct plating on all media tested. When it was lower than 103–104cfu/ml, listeria were isolated by direct plating only on LSAM and LSAM × 2A. When the difference was greater than 104cfu/ml, a previous enrichment was necessary to isolate them. LSAM and LSAM × 2A media performed better than the other media tested for isolating listeria by direct plating and improved their isolation from dairy products. This superior performance was evaluated by the ability of these media to support colony formation of different species ofListeriatested, the easy recognition of these colonies from those formed by other microorganisms and by their capacity to inhibit the natural microflora of these foods.

Procedures for Recovery of Stressed and Injured Cells of Yersinia Enterocolitica from Meat and Meat Products

1989 ◽  
Vol 52 (5) ◽  
pp. 360-362 ◽  
Author(s):  
ZHEKO KOUNEV
Keyword(s):  
Yersinia Enterocolitica ◽  
Agar Medium ◽  
Alkali Treatment ◽  
Meat Products ◽  
The Other ◽  
Step Procedure ◽  
Selective Agar ◽  
Agar Media ◽  
Phosphate Buffered Saline

A new three-step procedure (TSP) for the recovery of Yersinia enterocolitica 0:3 from frozen meat, salted and dried meat products, raw dried meat products, and cooked perishable sausages, has been developed. The TSP is based mainly on enrichment in 0.15 M phosphate-buffered saline at 25°C. In the TSP, selected dilutions of samples are enriched for 1, 2, 3, 4, 24, and 48 h and then plated onto nonselective and selective agar media after or without alkali treatment. Additional enrichment was performed with half of the samples at 25°C for 24 h, and the rest at 4°C for up to 2 wk, followed by alkali treatment and plating on selective agar medium. Recovery of Y. enterocolitica was better using the TSP than the other method used for isolating the organism from meats.

scholarly journals Antimicrobial resistance of bacterial isolates from dierent dairy products and their emergence in the food chain

2018 ◽  
Vol 11 (1) ◽  
pp. 45-57
Author(s):  
É. György ◽  
É. Laslo
Keyword(s):  
Risk Factors ◽  
Antibiotic Resistance ◽  
Foodborne Pathogens ◽  
Dairy Products ◽  
Preventive Measures ◽  
Agar Medium ◽  
Bacterial Isolates ◽  
E Coli ◽  
Selective Agar ◽  
Overall Resistance

Abstract The antibiotic resistance of foodborne pathogens represents a healthcare concern globally. This phenomenon has an increasing impact on medicine and economy. A total of 26 spoilage and pathogenic bacterial isolates originating from different dairy products have been screened against eight different antibiotics. Based on the type of the selective agar medium used for their isolation, the isolates were: five staphylococci isolates, six Vibrio isolates, two Pseudomonas sp. isolates, three Salmonella isolates, five E. coli isolates, and five coliform isolates. The overall resistance to the tested antimicrobials of the bacterial isolates was 31.73%, the majority being susceptible. Based on the results, there are isolates with multiple antibiotic patterns that can be possible risk factors and may call for preventive measures.

Un milieu gélosé pour le dénombrement direct de Staphylococcus aureus : milieu au plasma de porc pour S. aureus (PPSA)

1976 ◽  
Vol 22 (11) ◽  
pp. 1603-1611 ◽  
Author(s):  
J-J. Devoyod ◽  
Liliane Millet ◽  
G. Mocquot
Keyword(s):  
Staphylococcus Aureus ◽  
Dairy Products ◽  
Agar Medium ◽  
Egg Yolk ◽  
Plasma Medium ◽  
Large Numbers ◽  
Selective Agar ◽  
Coagulase Positive Staphylococci

A selective agar medium (pork plasma medium for S. aureus (PPSA)) enables the direct enumeration of coagulase-positive staphylococci. This medium is based on the Baird-Parker agar without egg yolk and is supplemented with pig plasma. Colonies of Staphylococcus aureus are surrounded by a halo of precipitated fibrin. When foods such as dairy products contain large numbers of egg yolk – negative strains of S. aureus, the PPSA agar has the advantage over egg yolk containing media such as Baird-Parker agar that fewer suspect colonies have to be confirmed.

INFLUENCE OF REFRIGERATED STORAGE ON DYE REDUCTION TIME OF MILKS

1952 ◽  
Vol 15 (1) ◽  
pp. 8-12 ◽  
Author(s):  
C. K. Johns
Keyword(s):  
Methylene Blue ◽  
Close Agreement ◽  
Raw Milk ◽  
Refrigerated Storage ◽  
Methylene Blue Reduction ◽  
Dye Reduction ◽  
Standard Plate ◽  
Plate Counts ◽  
The Difference ◽  
Better Than

Working with 100 weigh-can samples from 5 dairies it was found that icing for even 2 hours slightly retarded reduction of methylene blue; after 23 hours the effect was somewhat greater when the dye was present, but not when it was added just before incubation. With resazurin, on the other hand, there was better agreement when the dye was present during overnight storage. In no instance was the difference statistically significant. Methylene blue reduction times were in surprisingly close agreement with standard plate counts on the raw milk, while the correlation between reduction times (raw) and plate counts after laboratory pasteurization was better than was expected.

scholarly journals Development of New HS–SPME–GC–MS Technique to the Measurement of Volatile Terpenoid Profile of Milk

2021 ◽  
Author(s):  
Rita Székelyhidi ◽  
Erika Hanczné Lakatos ◽  
Beatrix Sik ◽  
Zsolt Ajtony
Keyword(s):  
Milk Fat ◽  
Dairy Products ◽  
Goat Milk ◽  
Raw Milk ◽  
Methyl Chavicol ◽  
Dairy Animals ◽  
Feeding Methods ◽  
Volatile Terpenoids ◽  
Better Than

AbstractThis study presented the development of such a HS–SPME–GC–MS technique, with the use of which, directly from the raw milk sample matrix, both qualitatively and quantitatively; the volatile terpenoids (α-pinene, sabinene, β-pinene, p-cymene, limonene, linalool, α-thujene, camphor, menthol, methyl chavicol, caryophyllene E, α-humulene) can be determined, derived from herbs eaten by the dairy animals by different feeding methods. Repeatability was less than 10% in the case of milk fat samples. The estimated limits of quantitation were between 2 and 16 ng/g. The lowest values were 2 ng/g for p-cymene and methyl chavicol; the highest value was 16 ng/g for caryophyllene. In the case of goat milk, the repeatability was better than 8% except for α-thujene. The estimated limits of quantitation were between 1 and 8 ng/g. The lowest values were 1 ng/g for β-pinene, p-cymene and limonene, and the highest value was 8 ng/g for linalool. In milk fat, the highest concentration was identified in caryophyllene E (470 ng/g) and α-humulene (430 ng/g), while the lowest concentration was in p-cymene (2 ng/g) and camphor (2 ng/g). In goat milk, limonene was present in all samples, but its amount varied depending on the type of consumed herb. Methyl chavicol and caryophyllene E were detected in goat’s milk only in one case. The former was detected in sage milk at 2.09 ng/g and the latter in tarragon milk at 2.28 ng/g. We have also successfully demonstrated that the feed consumed by dairy animals also affects the quality of dairy products.

Comparison of Three M17 Media for the Enumeration of Streptococcus thermophilus in Fermented Dairy Products

1992 ◽  
Vol 55 (12) ◽  
pp. 999-1002 ◽  
Author(s):  
R. JORDANO ◽  
CRISTINA E. SERRANO ◽  
MARÍA TORRES ◽  
J. SALMERON
Keyword(s):  
Dairy Products ◽  
Streptococcus Thermophilus ◽  
Fermented Milk ◽  
Fermented Dairy Products ◽  
Agar Media ◽  
The Difference ◽  
Fermented Dairy ◽  
Made In

Three M17 agar media for the enumeration of Streptococcus thermophilus in fermented dairy products, such as yogurt and other commercial fermented milk, were compared: CM785 Oxoid®, 15108 Merck®, and a M17 made in the laboratory. In all cases, the highest counts were taken on Oxoid® medium. The difference between the averages of the counts on the Oxoid® M17 and the laboratory-made M17 is significant, (P ≤ 0.05). However, the difference between the counts on the Oxoid® and Merck® media is not significant.

scholarly journals Studies on the isolation of Salmonella dublin

1975 ◽  
Vol 74 (3) ◽  
pp. 369-374 ◽  
Author(s):  
R. W. S. Harvey ◽  
T. H. Price
Keyword(s):  
Brilliant Green ◽  
The Other ◽  
Macconkey Agar ◽  
Salmonella Dublin ◽  
Selective Agar ◽  
Agar Media ◽  
Better Than

SUMMARYAbattoir drain swabs, bovine faeces and a few other veterinary samples were examined for the presence of Salmonella dublin. Three selective agar media and four enrichment broths were investigated. The two most efficient plating media were deoxycholate citrate agar and brilliant green MacConkey agar. Wilson and Blair's bismuth sulphite agar (de Loureiro's modification) was least successful. Selenite F broth, whether incubated at 37 or 43° C., was better than the other enrichment broths used which contained a triphenyl methane dye as one of the selective ingredients.

scholarly journals Isolation of Shigella sonnei by fluid media

1976 ◽  
Vol 77 (3) ◽  
pp. 341-348 ◽  
Author(s):  
T. H. Price
Keyword(s):  
Shigella Sonnei ◽  
Nutrient Broth ◽  
The Other ◽  
Direct Plating ◽  
Human Faeces ◽  
Fluid Media ◽  
The Difference ◽  
Better Than

SUMMARYSelenite F broth prepared in the laboratory from single ingredients was found to be significantly more efficient than nutrient broth in the isolation of Shigella sonnei from human faeces. It was more efficient than direct plating on deoxycholate citrate agar for diagnosing Sonne dysentery in a local outbreak. The difference was significant. There was, however, no significant advantage for enrichment over direct plating when stools posted from Bristol to Cardiff were examined.Laboratory prepared selenite F broth was preferable to the same medium purchased commercially from two different firms. The product of one firm was significantly better than that of the other.Two methods of sterilization of laboratory prepared selenite F broth were studied. Seitz filtered selenite was less inhibitory to the growth of small numbers of Shigella sonnei. Sterilization by heating in free steam for periods of 15 mm and over impaired the ability of selenite F broth to allow multiplication of small numbers of Shigella sonnei.

scholarly journals COMPARISON OF SLOVAK DAIRY PRODUCTS WITH AND WITHOUT ADDED VALUE SOLD BY COMMERCIAL CHAINS

2018 ◽  
Author(s):  
Marek Petriľák ◽  
Ing. Elena Horská ◽  
Jozef Šumichrast ◽  
Jozef Palkovič
Keyword(s):  
Dairy Products ◽  
Raw Materials ◽  
Raw Milk ◽  
Raw Material ◽  
Added Value ◽  
Cottage Cheese ◽  
Retail Chains ◽  
The Difference ◽  
Processed Products ◽  
Milk And Dairy Products

The share of products with higher added value is constantly decreasing in Slovakia's agri-food exports and the share of basic agricultural raw materials with low added value is increasing. Commercial retail chains sell especially products without added value. On the other side, products that have undergone a processing are imported from abroad. According to the latest survey of the Slovak Food Chamber of Agriculture in 2016, the share of Slovak products on retailers and retail chains is only 39.91%, with 38.9% in 2015 and 2014.with increase of only 1%. Most of the agri-food products produced in Slovakia are at most represented in commodities: eggs, milk, honey and at least in the following categories: processed vegetables, packaged meat and processed fruit. The main objective of presented paper is to show, that Slovak farmers rather sell raw milk instead of selling added value processed products. A big difference can be found between milk and dairy products, where up to 20% is the difference in the representation of these products in the commercial chains. This fact means, that the Slovak farmers produce enough milk, but it is convenient for them to sell milk as a raw material instead of processing it in their own direction and selling the processed products. Raw milk is exported abroad and then comes back to the Slovak market with an added value as processed product. The survey, which was carried out on all trade chains, showed that the share of Slovak milk in the chain is 63%. An important finding is also the presence of individual dairy products that are produced in Slovakia. The result of the survey showed that the largest share of Slovak dairy products in the domestic market is 51% cottage cheese and sweet / sour cream 55% lowest ripening cheese 40%and processed cheese and cheese spread 43%.

Removal of inelastically scattered electrons substantially increases phase contrast on frozen-hydrated molecules

1987 ◽  
Vol 45 ◽  
pp. 652-653
Author(s):  
John P. Langmore ◽  
Brian D. Athey
Keyword(s):  
Electron Diffraction ◽  
Phase Contrast ◽  
Low Dose ◽  
Dark Field ◽  
Biological Structure ◽  
Bright Field ◽  
Low Contrast ◽  
Negative Stain ◽  
The Difference ◽  
Better Than

Although electron diffraction indicates better than 0.3nm preservation of biological structure in vitreous ice, the imaging of molecules in ice is limited by low contrast. Thus, low-dose images of frozen-hydrated molecules have significantly more noise than images of air-dried or negatively-stained molecules. We have addressed the question of the origins of this loss of contrast. One unavoidable effect is the reduction in scattering contrast between a molecule and the background. In effect, the difference in scattering power between a molecule and its background is 2-5 times less in a layer of ice than in vacuum or negative stain. A second, previously unrecognized, effect is the large, incoherent background of inelastic scattering from the ice. This background reduces both scattering and phase contrast by an additional factor of about 3, as shown in this paper. We have used energy filtration on the Zeiss EM902 in order to eliminate this second effect, and also increase scattering contrast in bright-field and dark-field.

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