scholarly journals Determination of Listeria monocytogenes numbers at less than 10 cfu/g

2017 ◽  
Vol 56 (1) ◽  
pp. 25-30 ◽  
Author(s):  
K. Hunt ◽  
M. Vacelet ◽  
K. Jordan
Keyword(s):  
Listeria Monocytogenes ◽  
Detection Limit ◽  
Agar Plate ◽  
Foodborne Pathogen ◽  
Petri Dish ◽  
Food Samples ◽  
Plate Method ◽  
Pure Cultures ◽  
Response Current

AbstractListeria monocytogenes is a foodborne pathogen that causes a relatively rare foodborne disease called listeriosis, with a high mortality rate of 20%-30% and an undefined dose response. Current European Union regulations permit up to 100 colony-forming units (cfu)/g in food at the end of its shelf life, where the food has been shown not to support the growth of this pathogenic bacterium. Therefore, enumeration of L. monocytogenes at low numbers in food is important. The objective of this study was to reduce the detection limit of L. monocytogenes in food by a factor of 10. The International Organisation for Standardisation (ISO) 11290-2 method for enumeration of L. monocytogenes in food recommends spreading 0.1 mL of a 1:10 dilution of the food on the surface of an agar plate (detection limit 100 cfu/g), or 1.0 mL spread in equal parts on the surface of three agar plates (detection limit: 10 cfu/g). The pour-plate method (using 1 or 10 mL of an appropriate dilution) was compared to the spread-plate method using the ISO-approved chromogenic medium Agar Listeria according to Ottaviani and Agosti (ALOA). Using the pour-plate method, the colony morphology and halo formation were similar to the spread-plate method from pure cultures and inoculated foods. Using the pour-plate method in a 140 mm Petri dish, 10 mL of a 1:10 dilution of food allowed determination of numbers as low as 1 cfu/g. Applying this method, L. monocytogenes in naturally contaminated food samples were enumerated at numbers as low as 1-9 cfu/g.

Two-Day Yeast and Mold Enumeration Using the ISO-GRID® Membrane Filtration System in Conjunction with YM-11 Agar

1996 ◽  
Vol 59 (4) ◽  
pp. 416-419 ◽  
Author(s):  
PHYLLIS ENTIS ◽  
IRINA LERNER
Keyword(s):  
Membrane Filtration ◽  
Culture Medium ◽  
Food Product ◽  
Food Samples ◽  
Potato Dextrose Agar ◽  
Plate Method ◽  
Product Categories ◽  
Filtration System ◽  
Pure Cultures ◽  
Yeasts And Molds

A 2-day yeast and mold enumeration procedure using the ISO-GRID® membrane filtration system in conjunction with a new culture medium, YM-11 agar, was compared to the conventional 5-day pour plate method using antibiotic-supplemented potato dextrose agar. Performance of the new method was evaluated using both pure cultures of yeasts and molds and 275 food samples, representing 25 different food products. The 2-day ISO-GRID® method yielded counts equivalent to or significantly higher than the 5-day pour plate method in 23 of the 25 food product categories.

scholarly journals A new method for rapid detection of Listeria monocytogenes in food

2000 ◽  
Vol 18 (No. 3) ◽  
pp. 103-109 ◽  
Author(s):  
K. Zdeňková ◽  
K. Demnerová ◽  
G. Jeníková ◽  
J. Pazlarová
Keyword(s):  
Listeria Monocytogenes ◽  
Pcr Primers ◽  
Immunomagnetic Separation ◽  
Food Samples ◽  
Special Importance ◽  
Ground Meat ◽  
Specific Detection ◽  
Gene Encoding ◽  
Pcr Method

Listeria monocytogenes represents serious danger for human health. Thus detection of this pathogen in food, which represents its main means of entry into the organism, is a topic of special importance. The original classic methods for the determination of Listeria monocytogenes are in general laborious and time-consuming procedures. In order to address this issue we developed a new rapid method for specific detection of Listeria monocytogenes in food samples. The method consists of three steps: i) enrichment of food microflora (16 h), ii) selective isolation of Listeria sp. exploiting immunomagnetic separation (2–3 h) followed by iii) precise identification of Listeria sp. and Listeria monocytogenes using duplex PCR. PCR primers specific to part of 16S rRNA were used in order to identify the members of Listeria genus. The specific identification of Listeria monocytogenes was accomplished exploiting a pair of primers specific to gene encoding invasion-associated protein – iap (4–5 h). Amplification products, 1003 bp and 593 bp respectively, were separated by electrophoresis and visualized by UV detection. The optimized IMS-PCR method was used to test the presence of Listeria sp. and Listeria monocytogenes in food samples (ground meat, low-fat milk and cheese [olomoucké tvarůžky]). A comparison of the efficiency of the bacteria enrichment step by IMS and centrifugation was also performed. The analysis time including enrichment is less than 24 h. The detection limit for Listeria monocytogenes was found between 101–102 cfu per 25 g of food sample.

Electrocatalysis and Sensitive Determination of Sudan I at Fe3O4/Graphene Modified Glassy Carbon Electrodes

2013 ◽  
Vol 401-403 ◽  
pp. 775-778
Author(s):  
Su Xing Luo ◽  
Yuan Hui Wu ◽  
Hua Gou
Keyword(s):  
Iron Oxide ◽  
Detection Limit ◽  
Electrochemical Method ◽  
Food Samples ◽  
Carbon Electrodes ◽  
Glassy Carbon Electrodes ◽  
Sudan I ◽  
Anodic Peak Current ◽  
Sensitive Determination

The iron oxide/graphene (Fe3O4/rGO) nanocomposite modified electrode and the electrochemical properties of Sudan I were investigated. It was found the anodic peak current of Sudan I was linear with the concentration of Sudan I from 0.008 μM to 6 μM with a detection limit of 0.0005 μM (S/N=3). The regression equation was: Ipa (μA)=-0.8151-0.9651c (μM), R=0.9934. It was convenient and excellent sensitive electrochemical method for Sudan I determination. This electrochemical method was successfully applied to determine Sudan I in food samples.

scholarly journals Application of casein agar plate method for the determination of protease activity.

Eisei kagaku ◽  
1988 ◽  
Vol 34 (3) ◽  
pp. 241-247 ◽  
Author(s):  
KATSUSHI YOKOTA ◽  
NAOMI FURUSAWA ◽  
TETSUYA ABE ◽  
SEIKO TAKENAKA
Keyword(s):  
Protease Activity ◽  
Agar Plate ◽  
Plate Method

scholarly journals Real-Time PCR Method for the Rapid Detection and Quantification of Pathogenic Staphylococcus Species Based on Novel Molecular Target Genes

Foods ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 2839
Author(s):  
Eiseul Kim ◽  
Seung-Min Yang ◽  
Ji-Eun Won ◽  
Da-Young Kim ◽  
Da-Som Kim ◽  
...  
Keyword(s):  
Real Time ◽  
Target Genes ◽  
Foodborne Pathogen ◽  
Food Contamination ◽  
Disease Outbreaks ◽  
Molecular Target ◽  
Food Samples ◽  
Staphylococcus Capitis ◽  
Rapid Monitoring ◽  
Pure Cultures

Coagulase-positive Staphylococcus aureus is a foodborne pathogen considered one of the causes of food-related disease outbreaks. Like S. aureus, Staphylococcus capitis, Staphylococcus caprae, and S. epidermidis are opportunistic pathogens causing clinical infections and food contamination. The objective of our study was to develop a rapid, accurate, and monitoring technique to detect four Staphylococcus species in food. Four novel molecular targets (GntR family transcriptional regulator for S. aureus, phosphomannomutase for S. epidermidis, FAD-dependent urate hydroxylase for S. capitis, and Gram-positive signal peptide protein for S. caprae) were mined based on pan-genome analysis. Primers targeting molecular target genes showed 100% specificity for 100 non-target reference strains. The detection limit in pure cultures and artificially contaminated food samples was 102 colony-forming unit/mL for S. aureus, S. capitis, S. caprae, and S. epidermidis. Moreover, real-time polymerase chain reaction successfully detected strains isolated from various food matrices. Thus, our method allows an accurate and rapid monitoring of Staphylococcus species and may help control staphylococcal contamination of food.

scholarly journals In vitro antimicrobial activity of plant active components against Pseudomonas lundensis and Listeria monocytogenes

2020 ◽  
Author(s):  
Khabat Noori Hussein ◽  
Tímea Molnár ◽  
Richard Pinter ◽  
Adrienn Toth ◽  
Emna Ayari ◽  
...  
Keyword(s):  
Antimicrobial Activity ◽  
Listeria Monocytogenes ◽  
Inhibitory Concentration ◽  
Agar Plate ◽  
Diffusion Method ◽  
Active Components ◽  
Plate Method ◽  
Gradient Plate ◽  
Strong Antimicrobial Activity

AbstractThis work aimed to study the antimicrobial activity of eight various components of plant origin on the growth of Pseudomonas lundensis and Listeria monocytogenes. Different in vitro methods were used: agar plate diffusion, micro atmosphere, agar hole diffusion, micro-dilution, and gradient-plate method. In the first agar plate assay, p-cymene and γ-terpinene did not inhibit the growth of the tested bacteria therefore they were not used in further experiments. Both α-pinene and limonene were only partially effective, but these were screened only for their partial inhibition. The other four components completely inhibited the growth of the tested bacteria. Using the agar-well diffusion method showed that carvacrol and thymol were found to be the most effective active components, thymol had minimum inhibitory concentration (MIC) at 1.563 mg/mL, however, in the case of carvacrol, MIC was 7.813 μL/mL. Additionally, eugenol and camphor show the same results but in higher concentrations. Gradient plate method was used to determine MIC values, in which it has been proved that carvacrol and thymol possess strong antimicrobial activity, no growth of tested bacteria was observed with carvacrol (100 μL/mL), while thymol exhibited MIC of 1.887 mg/mL against P. lundensis and 0.943 mg/mL needed to show complete inhibition of Listeria monocytogenes. Further experiments are needed to determine the optimum concentrations of the active components against P. lundensis and L. monocytogenes.

scholarly journals Rapid Determination of Listeria monocytogenes by Automated Enzyme-Linked Immunoassay and Nonradioactive DNA Probe

2000 ◽  
Vol 83 (1) ◽  
pp. 86-88 ◽  
Author(s):  
Khalil F Kerdahi ◽  
Philip F Istafanos
Keyword(s):  
Listeria Monocytogenes ◽  
Rapid Determination ◽  
Food Samples ◽  
Dna Probe ◽  
Negative Results ◽  
Smoked Salmon ◽  
Colony Forming Units ◽  
Low Levels ◽  
Analytical Time

Abstract A rapid and reliable analytical method was developed to detect and confirm the presence of Listeria monocytogenes in raw and partially processed foods. Forty-nine food samples (25 mixed cut vegetable salad, 12 smoked salmon, and 12 sterile smoked salmon) were individually inoculated with high levels [10–100 colony forming units (cfu)/25 g sample] and low levels (1–10 cfu/25 g sample) of L. monocytogenes, and were screened using the Vitek Immuno Diagnostic Assay (VIDAS) Listeria monocytogenes (VIDAS LMO)]. Positive test results were confirmed as L. monocytogenes by nonradioactive DNA probe. All samples inoculated with high levels of L. monocytogenes were detected by VIDAS and 96% were confirmed as L. monocytogenes by DNA probe. VIDAS LMO detected 89% of samples inoculated with low levels of L. monocytogenes, and 87% of these were confirmed as positive by DNA probe. In addition, 12 other samples (4 from each of mixed cut vegetable salad, smoked salmon, and sterile smoked salmon) were inoculated with high levels of L. ivanovii, L. seeligeri, L. welshimeri, L. innocua, L. grayi, and L. murrayi. Samples were assayed by the same protocol and all gave negative results. Compared with the cultural method, the VIDAS LMO nonradioactive DNA probe combination is highly specific, discriminates between L. monocytogenes and all other Listeria species, and reduces analytical time.

Digestion of Food Samples for Total Mercury Determination

1985 ◽  
Vol 68 (5) ◽  
pp. 891-893
Author(s):  
Hon Way Louie ◽  
Danny Go ◽  
Mara Fedczina ◽  
Kevin Judd ◽  
John Dalins
Keyword(s):  
Detection Limit ◽  
Total Mercury ◽  
Inorganic Mercury ◽  
Food Samples ◽  
National Bureau ◽  
Mercury Determination ◽  
Albacore Tuna ◽  
Wide Range

Abstract A method of digestion by using a mixture of hydrochloric, nitric, and sulfuric acids has been developed for the determination of total mercury in a wide range of food samples. Good recoveries of mercury were obtained from NBS (National Bureau of Standards) Albacore Tuna and from food samples spiked with inorganic mercury. A detection limit of 0.01g mercury/g can be obtained.

scholarly journals Identification, subtyping and virulence determination of Listeria monocytogenes, an important foodborne pathogen

2006 ◽  
Vol 55 (6) ◽  
pp. 645-659 ◽  
Author(s):  
Dongyou Liu
Keyword(s):  
Listeria Monocytogenes ◽  
Molecular Mechanisms ◽  
Clinical Symptoms ◽  
Foodborne Pathogen ◽  
Future Research ◽  
Pathogenic Potential ◽  
Treatment Regimens ◽  
Detection And Identification ◽  
Control And Prevention

Listeria monocytogenes is an opportunistic intracellular pathogen that has become an important cause of human foodborne infections worldwide. Given its close relationship to other Listeria species and its tendency to produce non-specific clinical symptoms, the availability of rapid, sensitive and specific diagnostic tests for the differentiation of L. monocytogenes from other Listeria species is helpful for selecting appropriate treatment regimens. In addition, with L. monocytogenes comprising a diversity of strains of varying pathogenicity, the ability to precisely track the strains involved in listeriosis outbreaks and speedily determine their pathogenic potential is critical for the control and prevention of further occurrences of this deadly disease. Extensive research in recent decades has revealed significant insights regarding the molecular mechanisms of L. monocytogenes infection. This in turn has facilitated the development of laboratory procedures for enhanced detection and identification of L. monocytogenes, and has also contributed to the implementation of improved control and prevention strategies against listeriosis. The purpose of this review is to summarize recent progress in the species-specific identification, subtyping and virulence determination of L. monocytogenes strains, and to discuss future research needs pertaining to these important areas of listeriosis.

Sign in / Sign up

Export Citation Format

Share Document