Rapid qualitative and quantitative detection of Salmonella typhimurium using a single-step dual photometric/fluorometric assay.

A dual-signal photometric/fluorometric assay was established for rapid, qualitative, and quantitative detection of Salmonella typhimurium (S. typhimurium). This method was composed of two parts: (1) a single-step photometric (SSC) assay containing gold nanoparticles (AuNPs), poly-diallyldimethylammonium chloride (PDDA), and S. typhimurium-specific aptamer, and (2) a fluorescence (FL) assay containing carboxyl-modified CdSe/ZnS quantum dots (QDs-COOH). Users just need to drop samples contaminated with S. typhimurium into SSC assay; the apparent color change from red to blue can be observed in a short time (20 min). A smartphone app was developed to read the semiquantitative result. By subsequently adding one drop of FL assay into the reaction mixture, the generated fluorescence intensity reflected the concentration of S. typhimurium. The naked eye limit of detection (LOD) and fluorescent LOD were 103 cfu/mL and 10 cfu/mL, respectively. This method exhibited good selectivity. The reliability and practicability were verified by testing contaminated food, drinking water, and pets' urine.

Surveillance of Listeria monocytogenes: Early Detection, Population Dynamics, and Quasimetagenomic Sequencing during Selective Enrichment.

In this study, we addressed different aspects regarding the implementation of quasimetagenomic sequencing as a hybrid surveillance method in combination with enrichment for early detection of Listeria monocytogenes in the food industry. Different experimental enrichment cultures were used, comprising seven L. monocytogenes strains of different sequence types (STs), with and without a background microbiota community. To assess whether the proportions of the different STs changed over time during enrichment, the growth and population dynamics were assessed using dapE colony sequencing and dapE and 16S rRNA amplicon sequencing. There was a tendency of some STs to have a higher relative abundance during the late stage of enrichment when L. monocytogenes was enriched without background microbiota. When coenriched with background microbiota, the population dynamics of the different STs was more consistent over time. To evaluate the earliest possible time point during enrichment that allows the detection of L. monocytogenes and at the same time the generation of genetic information that enables an estimation regarding the strain diversity in a sample, quasimetagenomic sequencing was performed early during enrichment in the presence of the background microbiota using Oxford Nanopore Technologies Flongle and Illumina MiSeq sequencing. The application of multiple displacement amplification (MDA) enabled detection of L. monocytogenes (and the background microbiota) after only 4 h of enrichment using both applied sequencing approaches. The MiSeq sequencing data additionally enabled the prediction of cooccurring L. monocytogenes strains in the samples. IMPORTANCE We showed that a combination of a short primary enrichment combined with MDA and Nanopore sequencing can accelerate the traditional process of cultivation and identification of L. monocytogenes. The use of Illumina MiSeq sequencing additionally allowed us to predict the presence of cooccurring L. monocytogenes strains. Our results suggest quasimetagenomic sequencing is a valuable and promising hybrid surveillance tool for the food industry that enables faster identification of L. monocytogenes during early enrichment. Routine application of this approach could lead to more efficient and proactive actions in the food industry that prevent contamination and subsequent product recalls and food destruction, economic and reputational losses, and human listeriosis cases.

[Lectins in Viscum:a progress review].

Viscum plants,the evergreen perennial parasitic shrubs or subshrubs,are mainly distributed in tropical and subtropical regions. There are about 70 Viscum species around the world,including 11 species and one variety in China. Mistletoe lectins are typeⅡ ribosome-inactivating proteins( RIPs) extracted from Viscum plants with anticancer and immunoregulatory activities. Many studies have focused on the mistletoe lectins isolated from V. album in Europe and V. album var. coloratum distributed in South Korea,respectively,and several preparations,such as Iscucin Ⓡ,were developed and clinically applied for cancer treatment. Although Viscum plants are widely distributed in China,only a few studies of mistletoe lectins have been reported. The recent progress of mistletoe lectins was reviewed from extraction,purification,quantitative/qualitative detection,molecular structure,pharmacological activities,toxicities,and clinical application,aiming at providing a reference for in-depth research and utilization of mistletoe lectins produced in China.

Recent advances in photoluminescent fluorescent probe technology for food flavor compounds analysis.

The real-time, precise qualitative and quantitative sensing of food flavor compounds is crucial for ensuring food safety, quality, and consumer acceptance. As indicators for food flavor labeling, it is vital to delve deep into the specific ingredient and content of food flavor compounds to assess the food flavor quality, but still facing huge challenges. Photoluminescent fluorescent probe technology, with fast detection and high sensitivity, has shown immense potentials in detecting food flavor compounds. In this review, the classification and optical sensing mechanism of photoluminescent fluorescent probe technology are described in detail. Besides, challenges in applying photoluminescent fluorescent probe technology to analyze food flavor compounds are outlined to indicate future research directions. We hope this review can provide an insight for the applications of photoluminescent fluorescent probe technology in the evaluation of food flavor quality in future.

LSPR Tunable Ag@PDMS SERS Substrate for High Sensitivity and Uniformity Detection of Dye Molecules.

At present, the use of efficient and cost-effective methods to construct plasmonic surface-enhanced Raman scattering (SERS) substrates of high sensitivity, uniformity and reproducibility is still crucial to satisfy the practical application of SERS technology. In this paper, a localized surface plasmonic resonance (LSPR) tunable flexible Ag@PDMS substrate was successfully constructed by the low-cost bio-template-stripping method and magnetron sputtering technology. The theory proves that the local electromagnetic field enhancement and "hot spot" distribution is adjustable by modifying the size of the optical cavity unit in the periodicity nanocavity array structure. Experimentally, using rhodamine 6G (R6G) as the target analyte, the SERS performance of optimal Ag@PDMS substrate (Ag film thickness for 315 nm) was researched in detail, which the minimum detection limit was 10-11 M and the enhancement factor was calculated as 8.03 × 108, indicating its high sensitivity. The relative standard deviation (RSD) was calculated as 10.38%, showing that the prepared substrate had excellent electromagnetic field enhancement uniformity. At last, the trace detection of Crystal violet (CV, LOD = 10-9 M) and the simultaneous detection of three common dyes (R6G, CV and Methylene blue (MB) mixture) were also realized. This result suggests that the SERS substrate has a good application prospect in the quantitative and qualitative detection of dye molecules.

A colloidal gold immunochromatography for the detection of flumioxazin residues in fruits.

In this study, an excellent monoclonal antibody (mAb) was produced that could sensitively and specifically recognize Flu in fruit samples. The mAb belonged to the IgG2 subclass and had a half-inhibitory concentration (IC50 ) of 0.59 ng/ml and a limit of detection (LOD) of 0.13 ng/ml. A cross-reactivity test revealed that the mAb had good specificity for Flu. A gold nanoparticle-based lateral-flow immunochromatographic (ICA) strip was used for the rapid screening of Flu in fruit samples. The method had a visual cut-off value of 10 µg/kg for Flu in three different fruit samples when evaluated with the naked eye. The LODs were 5.25, 3.13, and 4.64 µg/kg for Flu in apples, grapes, and oranges, respectively, as obtained with the aid of a strip scan reader. Therefore, this ICA strip assay represented a potential tool for the detection of Flu in fruit samples.

Biofilm-forming microorganisms causing hospital-acquired infections from intravenous catheter: A systematic review.

The high prevalence of nosocomial infections is related to the use of medical insertion devices such as central venous catheters (CVCs). Most of the microorganisms causing nosocomial infections are biofilm producers, this characteristic allows them to adhere to abiotic surfaces and cause initial catheter infections that can lead to bloodstream infections. Our main goal in this systematic review was to evaluate the prevalence of biofilm among CVC-related infections, particularly among Intensive Care Unit (ICU) patients, in the studies applying different in vitro and in vivo methodologies. All studies reporting clinical isolates from patients with catheter-related nosocomial infections and biofilm evaluation published up to 24 June 2022 in the PubMed and Scopus databases were included. Twenty-five studies met the eligibility criteria and were included in this systematic review for analysis. Different methodologies were applied in the assessment of biofilm-forming microorganisms including in vitro assays, catheter-infected in vitro, and in vivo mouse models. The present study showed that between 59 and 100% of clinical isolates were able to form biofilms, and the prevalence rate of biofilm formation varied significantly between studies from different countries and regions. Among the clinical isolates collected in our study set, a wide variety of microorganisms including Gram-positive strains, Gram-negative strains, and Candida albicans were found. Many authors studied resistance mechanisms and genes related to biofilm development and surface adherence properties. In some cases, the studies also evaluated biofilm inhibition assays using various kinds of catheter coatings.

Glucose oxidase-induced colorimetric immunoassay for qualitative detection of danofloxacin based on iron (â ¡) chelation reaction with phenanthroline.

In this study, we developed a competitive colorimetric immunoassay for qualitative detection of DAN based on oxidation of iron (Ⅱ) (Fe2+) in the presence of glucose oxidase (GOx) and color change induced by Fe2+-phenanthroline (Phen) chromogenic system. Streptavidin (SA) acted as a linker between biotinylated anti-DAN-monoantibody (bio-mAb) and biotinylated GOx (bio-GOx) to form the immunocomplexes bio-mAb-SA-bio-GOx. In the absence of DAN, the immunocomplexes bio-mAb-SA-bio-GOx combining with coated DAN-ovalbumin (DAN-OVA) will be immobilized and catalyze glucose to produce H2O2. Fe2+ is oxidized to Fe3+ by H2O2, giving rise to a colorless result. In the presence of DAN, Fe2+ produces a chelation reaction with Phen, leading to orange-red color. Under optimal conditions, the detection limit (LOD) by naked eyes was 2.5 ng mL-1 in milk, chicken, beef, and pork samples. Low LOD, no matrix effect, and no signal reader requirement make it possibly applied to quickly screen DAN on site.

Lectins in Viscum:a progress review / 中国中药杂志

Viscum plants,the evergreen perennial parasitic shrubs or subshrubs,are mainly distributed in tropical and subtropical regions. There are about 70 Viscum species around the world,including 11 species and one variety in China. Mistletoe lectins are typeⅡ ribosome-inactivating proteins( RIPs) extracted from Viscum plants with anticancer and immunoregulatory activities. Many studies have focused on the mistletoe lectins isolated from V. album in Europe and V. album var. coloratum distributed in South Korea,respectively,and several preparations,such as Iscucin Ⓡ,were developed and clinically applied for cancer treatment. Although Viscum plants are widely distributed in China,only a few studies of mistletoe lectins have been reported. The recent progress of mistletoe lectins was reviewed from extraction,purification,quantitative/qualitative detection,molecular structure,pharmacological activities,toxicities,and clinical application,aiming at providing a reference for in-depth research and utilization of mistletoe lectins produced in China.

Inter-laboratory validation study of two immunochemical methods for detection of processed ruminant proteins.

In order to facilitate safe re-introduction of non-ruminant processed animal proteins (PAPs) in aqua feed, two immunoassays have been tested in an interlaboratory study for their capability to detect ruminant PAPs processed under European conditions. The sensitivity of the MELISA-TEK assay was improved by applying a specific extraction kit. Six approved blank pork and poultry samples were adulterated to produce 15 samples spiked at 0.5%, 1.0% and 2.0% with ruminant material, sterilised at either 133 °C or 137 °C. Fourteen participants investigated the 6 blanks and 15 spiked samples, making 21 samples for the final test. For both assays specificity and sensitivity were at 97% or higher. Concordance and accordance were higher than 95% with one exception. The results indicate that both assays provided correct results at 0.5% and higher for the detecting ruminant PAPs (sterilised at 133 °C) in non-ruminant PAPs. Given the 2% upper limit of ruminant PAPs in non-ruminant PAPs for avoiding an increase in BSE incidents, these methods are fit for monitoring non-ruminant PAPs intended for aqua feed.

Comparison of the effects of microfluidic paper-based immunoassay and traditional Western blot on the detection of target proteins / 基础医学与临床

Objective To achieve the goal of the qualitatively and relatively quantitatively analyze of the target pro-tein in a time-saving,labor-saving and reagents-saving way by the microfluidic paper-based immunoassay. Methods We chose MGMT as the target protein and compared the qualitative and semi-quantitative results of the MGMT ex-pression in the MCF7 cells which was treated with MGMT inhibitor, lomeguatrib, in both the traditional Western blot and the paper chip immunoassay. Results Microfluidic paper-based immunoassay can make the qualitative and relative quantitative detection on protein expression. Compared to the sensitivity of 1-5 ng of the traditional Western blot,the microfluidic paper-based immunoassay could detect as low as 10-25 pg of the protein. The sensitivity could be improved by 3 orders of magnitude. The entire operational duration took only 1 hour with less costed rea-gents being consumed. It maked the high-throughput protein detection as sensitive as the reverse phase protein as-says (RPPA) does. Conclusions The paper chip immunoassay could be performed qualitatively and semi-quanti-tatively to detect protein expression,and is more effective than that of traditional Western blot.

Comparison of the effects of microfluidic paper-based immunoassay and traditional Western blot on the detection of target proteins / 基础医学与临床

Objective To achieve the goal of the qualitatively and relatively quantitatively analyze of the target pro-tein in a time-saving,labor-saving and reagents-saving way by the microfluidic paper-based immunoassay. Methods We chose MGMT as the target protein and compared the qualitative and semi-quantitative results of the MGMT ex-pression in the MCF7 cells which was treated with MGMT inhibitor, lomeguatrib, in both the traditional Western blot and the paper chip immunoassay. Results Microfluidic paper-based immunoassay can make the qualitative and relative quantitative detection on protein expression. Compared to the sensitivity of 1-5 ng of the traditional Western blot,the microfluidic paper-based immunoassay could detect as low as 10-25 pg of the protein. The sensitivity could be improved by 3 orders of magnitude. The entire operational duration took only 1 hour with less costed rea-gents being consumed. It maked the high-throughput protein detection as sensitive as the reverse phase protein as-says (RPPA) does. Conclusions The paper chip immunoassay could be performed qualitatively and semi-quanti-tatively to detect protein expression,and is more effective than that of traditional Western blot.

Research on qualitative detection methods in medical equipment safety and quality control / 中国医学装备

Objective:To complete the medical equipment''s quality control on the premise of the lack of professional testing equipment.Methods: According to the working principle of instrument, to come up with corresponding simple and effective way to carry on the daily quality inspection, and make a qualitative conclusion that whether the instrument is qualified.Results:Effectively to ensure the safety and quality of medical equipment, medical equipment each year the average measurement test pass rate above 95% (bureau of quality and technical supervision measurement test results per year); perfectness ratio is around 98%.Conclusion: In the case of lack of professional testing equipment, through the integrated use of various effective means, can do the qualitative check that whether the performance of all sorts of equipment is qualified , achieve the goal of quality control.

Study on quality control of ELISA method for screening TORCH infection / 国际检验医学杂志

Objective Onto investigate the indoor quality control method for qualitatively detecting the laboratory indicators of TORCH infection (rubella virus IgG ,cytomegalovirus IgG and IgM ,toxoplasma IgG and IgM ) .Methods The statistical method , normal distribution data ,ratio and standard deviation of positive rate detected by the ELISA method were adopted ,1+2s was set as the out of control rules ,the semi Lerey‐Jennings quality control chart was drawn;the direct probability calculation method was a‐dopted for the non‐normal distribution data and small probability event .The testing data of 57 batches were retrospectively ana‐lyzed .Results The positive rate of rubella virus IgG was 86 .66% ,cytomegalovirus IgG/IgM positive rates were 98 .87% and 0 .13% ,toxoplasma gondii IgG/IgM positive rates were 2 .43% and 1 .71% ,the data of 151 ,3 ,5 ,176 ,27 samples had the critical value range of five indicators .The number of out of control was once for cytomegalovirus IgG ,once and 4 times for Toxoplasma gondii IgG/IgM .Conclusion The indoor quality control for the ELISA qualitative detection of TORCH infection can adopt the data of daily detection positive rate or negative rate for monitoring the false positive .The critical value range of specimens should be fur‐ther conducted the recheck or confirmation experiment .

Rapid Detection of Porcine Circovirus 2 Based on Double Molecular Beacons / 分析化学

A double-molecular beacons (DMB) based assay was developed for porcine circovirus 2(PCV2) detection. Two single-stranded DNA molecular beacons which could specifically hybridize with PCV2 genome DNA respectively in different sequence were designed according to the characteristics of the PCV2 genome sequences. The fluorescence signal was amplified 80 times by DMB, which was 2-4 times higher than that of single molecular beacon. Under the optimal conditions of 10 mmol/L MgCl2 , 20 mmol/L Tris-HCl (pH=8. 0), 40 ℃ and 30 min incubation time of DNA with DMB, the enlargement factor was increased linearly with DNA concentration over the range from 2 nmol/L to 200 nmol/L, with a detection limit of 1 nmol/L. The method was applied to detect PCV2 in genome of 18 swine fever samples and 8 PCV2 positive cases were found, which were confirmed by PCR method.