Single-shot 3D shape measurement based on RGB dot patterns and stereovision: retraction.

The referenced article [Opt. Express30, 28220 (2022)10.1364/OE.466148] has been retracted by the authors.

Inferring the distribution of norovirus in individual oysters below the limit of quantification by pooled sampling.

Norovirus (NoV) in oysters is a food safety risk of much concern. In order to assess the risk of the exposure, the distribution of the number of NoV copies contained in each oyster should be acquired first for comprehensively quantifying the associated risks. However, the part of the distribution below the limit of quantification cannot be obtained directly by laboratory detecting methods, which hampers accurate assessment. To tackle this challenging problem, a systematic method (Distribution Inference Method by Pooled Sampling) is proposed to infer the unobservable part of distribution based upon all measurements of the pooled samples with n = 2. Using convolutional integrals and real-coded genetic algorithm for inferring, this method has neither requirements for the type or properties of the original distribution, nor requirements for historical data, even nor requirements for the relationship between observable and unobservable parts of the distribution. A series of experiments were conducted on simulated datasets of a variety of types, including normal distribution, uniform distribution, gamma distribution, lognormal distribution, zero-inflated Poisson distribution, their combinations, and even their splicing, covering common distribution types in oyster NoV scenario and more general scenarios. The results show that almost all inferred simulation data and their original counterparts passed Kolmogorov-Smirnov tests, which implies that they are essential of the same distribution. Based on this method, a ready-to-use web system was developed for researchers to infer their original distribution with pooled-sampling measurements from the detection of NoV or even other substances.

Quantitative microbiological risk assessment of nontyphoidal Salmonella in ground pork in households in Chengdu, China.

Foodborne disease caused by nontyphoidal Salmonella (NTS) is one of the most important food safety issues worldwide. The objectives of this study were to carry out microbial monitoring on the prevalence of NTS in commercial ground pork, investigate consumption patterns, and conduct a quantitative microbiological risk assessment (QMRA) that considers cross-contamination to determine the risk caused by consuming ground pork and ready-to-eat food contaminated during food handling in the kitchen in Chengdu, China. The food pathway of ground pork was simplified and assumed to be several units according to the actual situation and our survey data, which were collected from our research or references and substituted into the QMRA model for simulation. The results showed that the prevalence of NTS in ground pork purchased in Chengdu was 69.64% (95% confidence interval [CI], 60.2-78.0), with a mean contamination level of -0.164 log CFU/g. After general cooking, NTS in ground pork could be eliminated (contamination level of zero). The estimated probability of causing salmonellosis per day was 9.43E-06 (95% CI: 8.82E-06-1.00E-05), while the estimated salmonellosis cases per million people per year were 3442 (95% CI: 3218-3666). According to the sensitivity analysis, the occurrence of cross-contamination was the most important factor affecting the probability of salmonellosis. To reduce the risk of salmonellosis caused by NTS through ground pork consumption, reasonable hygiene prevention and control measures should be adopted during food preparation to reduce cross-contamination. This study provides valuable information for household cooking and food safety management in China.

A spatially-controlled DNA triangular prism nanomachine for AND-gated intracellular imaging of ATP in acidic microenvironment.

A DNA triangular prism nanomachine (TPN)-based logic device for intracellular AND-gated imaging of adenosine triphosphate (ATP) has been constructed. By using i-motif sequences and ATP-binding aptamers as logic control units, the TPN logic device is qualified to respond to the acidic environment and ATP in cancer cell lysosomes. Once internalized into the lysosome, the specific acidic microenvironment in lysosome causes the i-motif sequence to fold into a tetramer, resulting in compression of DNA tri-prism. Subsequently, the split ATP aptamer located at the tip of the collapsed triangular prism binds stably to ATP, which results in the fluorescent dyes (Cy3 and Cy5) modified at the ends of the split aptamer being in close proximity to each other, allowing Förster Resonance Energy Transfer (FRET) to occur. The FRET signals are excited at a wavelength of 543 nm and can be collected within the emission range of 646-730 nm. This enables the precise imaging of ATP within a cell. We also dynamically operate AND logic gates in living cells by modulating intracellular pH and ATP levels with the help of external drugs. Owing to the AND logic unit on TPN it can simultaneously recognize two targets and give corresponding intelligent logic judgment via imaging signal output. The accuracy of molecular diagnosis of cancer can be improved thus eliminating the false positive signal of single target-based detection. Hence, this space-controlled TPN-based logical sensing platform greatly avoids sensitivity to extracellular targets during the cell entry process, providing a useful tool for high-precision imaging of the cancer cell's endogenous target ATP.

Molecular and biochemical characterization of two 4-coumarate: CoA ligase genes in tea plant (Camellia sinensis).

KEY MESSAGE: Two 4-coumarate: CoA ligase genes in tea plant involved in phenylpropanoids biosynthesis and response to environmental stresses. Tea plant is rich in flavonoids benefiting human health. Lignin is essential for tea plant growth. Both flavonoids and lignin defend plants from stresses. The biosynthesis of lignin and flavonoids shares a key intermediate, 4-coumaroyl-CoA, which is formed from 4-coumaric acid catalyzed by 4-coumaric acid: CoA ligase (4CL). Herein, we report two 4CL paralogs from tea plant, Cs4CL1 and Cs4CL2, which are a member of class I and II of this gene family, respectively. Cs4CL1 was mainly expressed in roots and stems, while Cs4CL2 was mainly expressed in leaves. The promoter of Cs4CL1 had AC, nine types of light sensitive (LSE), four types of stress-inducible (SIE), and two types of meristem-specific elements (MSE). The promoter of Cs4CL2 also had AC and nine types of LSEs, but only had two types of SIEs and did not have MSEs. In addition, the LSEs varied in the two promoters. Based on the different features of regulatory elements, three stress treatments were tested to understand their expression responses to different conditions. The resulting data indicated that the expression of Cs4CL1 was sensitive to mechanical wounding, while the expression of Cs4CL2 was UV-B-inducible. Enzymatic assays showed that both recombinant Cs4CL1 and Cs4CL2 transformed 4-coumaric acid (CM), ferulic acid (FR), and caffeic acid (CF) to their corresponding CoA ethers. Kinetic analysis indicated that the recombinant Cs4CL1 preferred to catalyze CF, while the recombinant Cs4CL2 favored to catalyze CM. The overexpression of both Cs4CL1 and Cs4CL2 increased the levels of chlorogenic acid and total lignin in transgenic tobacco seedlings. In addition, the overexpression of Cs4CL2 consistently increased the levels of three flavonoid compounds. These findings indicate the differences of Cs4CL1 and Cs4CL2 in the phenylpropanoid metabolism.

Single-shot 3D shape measurement based on RGB dot patterns and stereovision.

One-shot projection structured light 3D measurement is a method to establish the stereo matching relationship and reconstruct 3D shape by projecting one pattern. However, the traditional stereo matching algorithm does not solve the problem of low matching accuracy and matching efficiency, which fundamentally limits the accuracy of 3D measurement. As the projector and imaging systems have daily higher resolution and imaging quality, RGB dots projection has more application prospects because of its ability to establish a stereo matching relationship through one projection. In this work, we proposed a single-shot 3D measurement method using line clustering stereo matching, and model correction methods. The projected RGB dots are extracted by slope differenced distribution and area constrained erosion method. Area constrained erosion can solve the problem of the segmented connected blobs caused by insufficient projection resolution. The clustering stereo matching method is utilized to coarse match the segmented center red points. A model correction method is utilized to restore and constrain the pattern that cannot be imaged. Experimental results demonstrated that our method achieves the best accuracy of about 0.089mm, better than the traditional disparity and RGB line method, which may shed light on the proposed method can accurately reconstruct the 3D surface.

Ultrasensitive Uracil-DNA Glycosylase Activity Assay and Its Inhibitor Screening Based on Primer Remodeling Jointly via Repair Enzyme and Polymerase.

The development of isothermal nucleic acid amplification techniques has great significance for highly sensitive biosensing in modern biology and biomedicine. A facile and robust exponential rolling circle amplification (RCA) strategy is proposed based on primer-remodeling amplification jointly via a repair enzyme and polymerase, and uracil-DNA glycosylase (UDG) is selected as a model analyte. Two kinds of complexes, complex I and complex II, are preprepared by hybridizing a circular template (CT) with a uracil-containing hairpin probe and tetrahydrofuran abasic site mimic (AP site)-embedded fluorescence-quenched probe (AFP), respectively. The target UDG specifically binds to complex I, resulting in the generation of an AP site, followed by cleavage via endonuclease IV (Endo IV) and the successive trimming of unmatched 3' terminus via phi29 DNA polymerase, thus producing a useable primer-CT complex that actuates the primary RCA. Then, numerous complex II anneal with the first-generation RCA product (RP), generating a complex II-RP assembly containing AP sites within the DNA duplex. With the aid of Endo IV and phi29, AFP, as a pre-primer in complex II, is converted into a mature primer to initiate additional rounds of RCA. So, countless AFPs are cleaved, releasing remarkably strong fluorescent signals. The biosensor is demonstrated to enable rapid and accurate detection of the UDG activity with an improved detection limit as low as 4.7 × 10-5 U·mL-1. Moreover, this biosensor is successfully applied for UDG inhibitor screening and complicated biological samples analysis. Compared to the previous exponential RCA methods, our proposed strategy offers additional advantages, including excellent stability, optional design of CT, and simplified operating steps. Therefore, this proposed strategy may create a useful and practical platform for ultrasensitive detection of low levels of analytes in clinical diagnosis and fundamental biomedicine research.

Prevalence, Antimicrobial Resistance, and Molecular Characteristics of Staphylococcus aureus and Methicillin-Resistant Staphylococcus aureus from Retail Ice Cream in Shaanxi Province, China.

Staphylococcus aureus (S. aureus) is one of the major opportunistic foodborne pathogens as well as a source of human and animal infections. As surveillance of S. aureus and methicillin-resistant Staphylococcus aureus (MRSA) is limited in ice cream, a total of 240 ice cream samples were collected from three cities in Shaanxi province, China, and screened for S. aureus. All isolates were characterized by antimicrobial susceptibility testing, staphylococcal protein A typing, multilocus sequence typing, enterobacterial repetitive intergenic consensus typing, virulence, and resistance genes. S. aureus was recovered from 10 (4.2%) ice cream samples (13 isolates) with average count from 10 to 100 colony-forming units per gram in all cases. Resistance to amoxicillin/clavulanic acid, penicillin, and trimethoprim/sulfamethoxazole (each 100.0%) was most frequently observed, followed by ampicillin (76.9%), erythromycin (46.2%), ceftriaxone (30.8%), and cefoxitin (15.4%). A total of five types of antimicrobial resistance genes were detected, including ß-lactam (blaZ and mecA), macrolide (ermB and ermC), tetracycline (tetK), aminoglycoside [aac(6')/aph(2') and aph(3')-III], and trimethoprim (dfrG). All of the strains harbored at least one staphylococcal enterotoxins gene. The commonly detected virulence genes were selw and hld (100.0%), followed by selx (92.3%); hla (84.6%); pvl (76.9%); seg, sem, and sen (each 38.5%); sei, seo, and hlb (each 30.8%); sea, seb, selu, and sely (each 23.1%); sed, sej, sek, sep, and seq (each 15.4%); and ser (7.7%). ST5-t002, ST7-t091, and ST5225-t4911 (each 15.4%) were the predominant clones, followed by ST5-t045/t105, ST6-t701/t15417, ST25-t078, ST188-t189, and ST398-t034 (each 7.7%). Among the 13 strains of S. aureus, 2 isolates were detected as MRSA (15.4%), and the molecular type belonged to ST5225-IVa-t4911. Using a 98.8% similarity cutoff, the 13 isolates were divided into 5 clusters (I-1 to I-5). These results demonstrated that the prevalence of S. aureus and MRSA was low in ice cream. However, these isolates exhibited a high level of potential pathogenicity, which represents a potential health hazard for consumers.

Accurate and Nonpurified Identification of Extracellular Vesicles Using Dual-Binding Recognition Mode.

Circulating extracellular vesicles (EVs) are promising biomarkers for the early diagnosis and prognosis of cancer in a non-invasive manner. However, the rapid and accurate identification of EVs in complex biological samples is technically challenging, which is attributed to the requirement of extensive sample purification and unsatisfactory detection accuracy due to the disturbance of interfering proteins. Herein, a simultaneous binding of double-positive EV membrane protein-based recognition mode (DRM) is proposed. By the combination of DRM-mediated toehold activation and G-quadruplex DNAZyme-catalyzed etching of Au@Ag nanorods (Au@Ag NRs), we have developed an accurate, non-purified, low-cost, and visual strategy for EV identification. The synchronous binding of double-positive proteins on EV membranes is validated by confocal laser scanning microscopy analysis. This approach exhibits excellent specificity and sensitivity toward EVs ranging from 1.0 × 105 to 1.0 × 109 particles/mL with a detection limit of 6.31 × 104 particles/mL. Moreover, we have successfully realized non-purified EV quantification in complex biological media. In addition, target-initiated catalyzed hairpin assembly (CHA) is integrated with G-quadruplex DNAZyme-catalyzed color variation of Au@Ag NRs; thus, low-background EV detection can be achieved by the naked eye. Furthermore, our strategy is easy to adapt to high-throughput formats by using an automatic microplate reader, which could be expected to meet the requirements for high-throughput detection of clinical samples. With its capacities of rapidness, portability, affordability, high throughput, non-purification, and visual detection, this strategy could provide a practical tool for accurate identification of EVs and early diagnosis of cancer.

A three-dimensional dynamic DNA walker-mediated branching hybridization chain reaction for the ultrasensitive fluorescence sensing of ampicillin.

In this study, a novel, rapid and ultrasensitive fluorescence strategy using the three-dimensional (3D) dynamic DNA walker (DW)-induced branched hybridization chain reaction (bHCR) has been proposed for the detection of ampicillin (AMP). The sensing system was composed of an Nt·Bbvcl-powered DNA walker blocked by an AMP aptamer, hairpin-shaped DNA track probe (TP) and four kinds of metastable hairpin probes as the substrates of bHCR, which triggered the formation of the split G-quadruplex as the signal molecule. Due to the reasonable design, the specific binding between AMP and its aptamer activated the DW, and the DW moved on the surface of the gold nanoparticles (AuNPs) with the help of Nt·Bbvcl to produce primer probes (PPs), which induced bHCR. The products of the bHCR gathered two split G-quadruplex sequences together to form one complete G-quadruplex. The formed G-quadruplex emitted a strong fluorescence signal in the presence of thioflavin-T (ThT) to achieve the purpose of detecting AMP. The sensitivity of this method was greatly improved by the use of the 3D DNA walker and bHCR. The split G-quadruplex enhanced the signal-to-noise ratio (SNR). Under the optimal experimental conditions, a good correlation was obtained between the fluorescence intensity of the sensing system and the concentration of AMP ranging from 5 pM to 500 nM with a limit of detection (LOD) of 3.68 pM. Simultaneously, the method has been applied to the detection of antibiotics in spiked milk samples with satisfactory results.

Target-swiped DNA lock for electrochemical sensing of miRNAs based on DNAzyme-assisted primer-generation amplification.

As an extremely important post-transcriptional regulator, miRNAs are involved in a variety of crucial biological processes, and the abnormal expressions of miRNAs are closely related to a variety of diseases. In this work, for the first time, we designed a nucleic acid lock nanostructure for specific detection of miRNA-21, which changes the self-structure to "active conformation" by binding the target, in order to generate triggers to initiate the subsequent reaction. Emphatically, this flexible nucleic acid lock is capable of self-cleaving without the assistance of external component, overcoming the disadvantages of the complex design and requiring protease assistance in traditional nanostructure. Moreover, the combination of DNAzyme and RCA technology not only greatly improves the efficiency of signal amplification but also enables primer generation to simultaneous cascade RCA amplification. Additionally, the electrochemical detection technology based on silver nanoclusters overcomes the shortcomings of traditional detection methods such as low sensitivity and complex operation. The detection limit achieved was 9.3 aM with a wide dynamic response ranging from 10 aM to 100 pM (at the DPV peak of - 0.5 V), which is comparable to most of the reported studies. Therefore, our work provided an ultra-sensitive way for the detection of miRNAs using nanostructures and revealed an effective means for disease theranostics and cancer diagnosis. In this work, for the first time, we designed a nucleic acid lock nanostructure based on its self-structural transformation for the specific detection of miRNA. And the combination of DNAzyme and cascade RCA reaction greatly improved the signal amplification efficiency.

[Preliminary quantitative risk assessment of the effect of Salmonella on human health in retail fresh pork].

OBJECTIVE: A quantitative microbiological risk assessment was conducted for Salmonella spp. in fresh pork from retail stores to consumers in China in order to provide evidence for adopting effective risk management measures. METHODS: The national food safety and risk monitoring data was used to estimate the initial contamination level of Salmonella in the retail fresh pork. The growth model and the cross-contamination model of Salmonella were referenced from the ComBase data base and scientific literature, respectively. Then the human health risk was predicted by the consumption of Salmonella-contaminated fresh pork and the Beta-Poisson dose-response model. RESULTS: The number of Salmonellosis per year among 1 million residents due to fresh pork was estimated to be 4748.The sensitivity analysis showed that the risk of Salmonellosis was mainly and positively correlated with the preparation rate of ready to eat food, the consumption quantity of pork, the initial contamination level of Salmonella in fresh pork, and the proportion of improper cleaning of knives and chopping boards. When the contamination level of Salmonella in fresh pork is controlled below 1 CFU/g, the average probability of illness will be reduced by 59.39%; the average probability of illness will be reduced by 58.97% by increasing the ratio of complete cleaning of chopping boards or the separation ratio of chopping boards for raw and ready-to-eat food to 90%. CONCLUSION: The risk could be effectively reduced by controlling the concentration of Salmonella contamination in retail pork or improving hygiene practices.

Antibiotic Resistance Patterns of Staphylococcus aureus Isolates from Retail Foods in Mainland China: A Meta-Analysis.

Foodborne Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), is increasingly threatening human health. Pooled prevalence rates of S. aureus contamination have been extensively studied in retail food products in mainland China, but data regarding antibiotic resistance rates of S. aureus remain scattered. This study was designed to collect researches published between 2007 and 2017 in mainland China and to evaluate the antibiotic resistance of S. aureus from retail foods using a meta-analytic approach. We systematically searched the China National Knowledge Infrastructure (CNKI) and Web of Science databases to identify peer-reviewed literature. A number of multilevel random-effects models were fitted to estimate mean occurrence rates of antibiotic-resistant S. aureus, and subgroup analyses were performed to compare antibiotic resistance rates of S. aureus throughout the years and among the methods to determine the antimicrobial susceptibility. Among the considered antibiotics, S. aureus showed the highest resistance rate to penicillin G (87%, 95% confidence interval [CI] 83-90%), followed by ampicillin (72%, 95% CI 62-81%) and erythromycin (41%, 95% CI 36-46%). MRSA showed the highest resistance rate to ampicillin (98%, 95% CI 89-100%), followed by oxacillin (97%, 95% CI 80-100%) and penicillin G (96%, 95% CI 89-99%). Multidrug resistance (MDR) of S. aureus was most frequently observed to three antibiotics (17%, 95% CI 12-22%), and MRSA showed the highest resistance rate to four antibiotics (24%, 95% CI 5-67%). Subgroup analyses results proved that sources of heterogeneity among studies were neither publication year nor detection method. In conclusion, the meta-analysis showed that ß-lactam antibiotics resistance of S. aureus and MRSA strains isolated from retail foods remained the most serious, and MDR of S. aureus and MRSA were also observed. Therefore, it is important to monitor the antibiotic resistance of S. aureus and MRSA in food chain, and food safety measures should be taken to reduce the transmission of this bacterium from foods to human beings.

[Epidemic condition and molecular subtyping of ciprofloxacin and cefotaxime co-resistant Salmonella Indiana isolated from retail chicken carcasses in six provinces, China].

OBJECTIVE: To elucidate the epidemic condition and molecular subtyping of ciprofloxacin and cefotaxime co-resistant Salmonella Indiana (S. Indiana) isolated from retail chicken carcasses in six provinces of China. METHODS: A total of 2 647 Salmonella strains isolated from retail chicken carcasses collected from six provinces of China were subjected to antimicrobial susceptibility testing. All Salmonella isolates co-resistant to ciprofloxacin and cefotaxime were further characterized by serotyping, extended-spectrum beta-lactamases (ESBLs) producing strains screening and pulsed field gel electrophoresis (PFGE) typing. RESULTS: Among 2 629 Salmonella isolates tested, 227 (8.52%) isolates were co-resistant to ciprofloxacin and ceftazidime/cefotaxime (Beijing: 11.67% (99/874), Jilin: 8.20% (60/726), Guangdong: 1.39% (7/502), Jiangsu: 15.61% (42/260), Shaanxi: 8.56% (16/186), Inner Mongolia: 0 (0/81)), and 224 of them were identified as S. Indiana. 213 (95.10%) isolates of S. Indiana were ESBLs producing strains. All ciprofloxacin and cefotaxime co-resistant S. Indiana isolates developed a multi-drug resistant profile and 17.86% (40/224) of them were resistant to all antibiotics tested except carbapenems, and 50.89% (114/224) of them resistant to 9 antibiotics, additionally, 25.45% (57/224) of them showed multi-drug resistance to 8 antibiotics. All ciprofloxacin and cefotaxime co-resistant S. Indiana isolates were divided into 32 PFGE clusters and 150 PFGE patterns. Strains of S. Indiana from same or different sampling site and time seemed to either share the same PFGE patterns or be differential to each other in different regions. CONCLUSION: The results indicated that chicken carcasses collected from parts of China were heavily contaminated by ciprofloxacin and cefotaxime co-resistant S. Indiana and could serve as an important reservoir of ciprofloxacin and cefotaxime co-resistant Salmonella. Molecular subtyping results indicated that cross contamination or common pollution source might be in these strains.

[Study on simultaneous contamination of Salmonella and Campylobacter in retail chicken carcasses in Beijing].

OBJECTIVE: To elucidate the simultaneous contamination of Salmonella and Campylobacter in retail chicken carcasses in Beijing and to carry out the serological typing of all Salmonella isolates as well as the identification of Campylobacter at the species level. METHODS: A total of 33 chicken carcasses were collected from Beijing supermarkets and farm's trade markets from May to July. All samples were enumerated for Salmonella and Campylobacter. All Salmonella isolates obtained were further serotyped and Campylobacter were identified at the species level. RESULTS: Totally, 19 samples (19/33, 57.6%) and 5 samples (5/33, 15.2%) were positive for Salmonella with the mean level of 119.4 MPN/100g and Campylobacter with the mean level of 58.6 CFU/g, respectively. In terms of Salmonella, 166 isolates with 14 serotypes were obtained. Salmonella Enteritidis was the most common serovar detected followed by S. Indiana. Serovar diversity was very high in all Salmonella isolates and various Salmonella serovars were detected in the same chicken carcass. A total of 11 serovar distribution spectrums were found and S. Enteritidis in combination with S. Indiana was the predominant. CONCLUSION: The retail chicken carcasses in Beijing collected from May to July were heavily contaminated by Salmonella with high serovar diversity.

Enumeration and characterization of Salmonella isolates from retail chicken carcasses in Beijing, China.

Epidemiological reports have implicated contaminated raw or undercooked chicken as primary vehicles of Salmonella transmission to human beings. Risk assessments relating to Salmonella contamination of poultry products in China are frequently hampered by the lack of quantitative data. In this study, whole chicken carcasses (n=395) were collected from the retail markets of Beijing, and the level of Salmonella contamination was enumerated by most probable number (MPN) analysis and all Salmonella isolates were further characterized for their serotypes and antimicrobial resistance. Overall, 49.9% (197/395) of the retail whole chicken carcasses were contaminated by Salmonella and the MPN values ranged from 1.5 to >550 MPN/100 g. The 50% percentile of Salmonella MPN value was 7.5 MPN/100 g in chicken carcass. The predominant serotypes isolated were Salmonella Enteritidis (n=309, 94 samples), Salmonella Indiana (n=205, 54 samples) and Salmonella Infantis (n=89, 23 samples). Multidrug-resistant Salmonella isolates were recovered from 100 chicken carcass samples; 102 isolates (from 41 chicken carcasses) even showed resistance to both ciprofloxacin and cefotaxime. Our findings showed a high prevalence of Salmonella contamination in retail chicken carcasses, which could be a source of exposure for consumers to multidrug-resistant isolates. This study provided baseline enumeration data for the risk assessment and evaluation of new control measures of Salmonella contamination in retail chicken products.

Characterization of Pseudomonas spp. contamination and in situ spoilage potential in pasteurized milk production process.

To investigate the prevalence of Pseudomonas in the pasteurized milk production process and its effect on milk quality, 106 strains of Pseudomonas were isolated from the pasteurized milk production process of a milk production plant in Shaanxi Province, China. The protease, lipase and biofilm-producing capacities of the 106 Pseudomonas strains were evaluated, and the spoilage enzyme activities of their metabolites were assessed by simulating temperature incubation in the refrigerated (7 °C) and transport environment (25 °C) segments and thermal treatments of pasteurization (75 °C, 5 min) and ultra-high temperature sterilization (121 °C, 15 s). A phylogenetic tree was drawn based on 16S rDNA gene sequencing and the top 5 strains were selected as representative strains to identify their in situ spoilage potential by examining their growth potential and ability to hydrolyze proteins and lipids in milk using growth curves, pH, whiteness, Zeta-potential, lipid oxidation, SDS-PAGE and volatile flavor compounds. The results showed that half and more of the isolated Pseudomonas had spoilage enzyme production and biofilm capacity, and the spoilage enzyme activity of metabolites was affected by the culture temperature and sterilization method, but ultra-high temperature sterilization could not completely eliminate the enzyme activity. The growth of Pseudomonas lundensis and Pseudomonas qingdaonensis was less affected by temperature and time, and the hydrolytic capacity of extracellular protease and lipase secreted by Pseudomonas lurida was the strongest, which had the greatest effect on milk quality. Therefore, it is crucial to identify the key contamination links of Pseudomonas, the main bacteria responsible for milk spoilage, and the influence of environmental factors on its deterioration.

Microbial contamination, community diversity and cross-contamination risk of food-contact ice.

Ice is widely used in the food industry, as an ingredient (edible ice) directly added to food or as a coolant (food-contact ice) for fresh food preservation along the cold chain. However, it has been shown that food-contact ice are easily polluted by pathogens, potentially endangering the public's health. In the present study, the hygiene status of food-contact ice collected from various sources (local farmer markets, supermarkets, and restaurants) was evaluated through the quantitative estimation of total bacterial counts and coliform counts as well as the prevalence of foodborne pathogenic bacteria (Staphylococcus aureus, Vibrio parahaemolyticus, Salmonella, Listeria monocytogenes, Shigella). The average levels of total bacterial counts in the ice for preserving the aquatic products, poultry meat and livestock meat are 4.88, 4.18 and 6.11 log10 CFU/g, respectively. Over 90 % of the food-contact ice were positive for coliforms. The detection rate of S. aureus in all the food-contact ice samples was highest, followed by Salmonella, V. parahaemolyticus and L. monocytogenes, and Shigella was not detected. In addition, the bacterial community diversity of food-contact ice was analyzed with high-throughput sequencing. The dominant bacteria taxa in food-contact ice are heavily dependent on the environment of sampling sites. The predicted phenotypes of biofilm forming, oxidative stress tolerance, mobile element containing and pathogenesis were identified in the bacteria taxa of food-contact ice, which should be carefully evaluated in future work. Finally, the cross-contamination models of pathogen transfer during ice preservation were established. The results showed that the transfer rates of ice-isolated S. aureus between food and ice were significantly higher than that of V. parahaemolyticus. The binomial distribution B(n, p) exhibited a better fitness to describe the pathogen transfer during ice preservation when the transfer rate was low, in turn, the transfer rate-based probability model showed a better fit to the data when the transfer rate was high. Monte Carlo simulation with Latin-Hypercube sampling was carried out to predict the contamination levels of S. aureus and V. parahaemolyticus on food as the result of cross contamination during ice preservation ranging from -2.90 to 2.96 log10 CFU/g with a 90 % confidence interval. The findings of this work are conducive to a comprehensive understanding of the current hygiene status of food-contact ice, and lay a theoretical foundation for the risk assessment of cross-contamination during ice preservation.

A micro-nano interface integrated SERS-based microfluidic sensor for miRNA detection using DNAzyme walker amplification.

BACKGROUND: Precise and specific miRNA detection plays a vital role in exploring development mechanisms of cancer disease, thereby it can significantly improve relevant prevention and treatment strategies. RESULTS: In this work, a surface-enhanced Raman spectroscopy (SERS)-based microfluidic chip has been devised with a microcone array SERS substrate (MCASS) for the miR-141 detection. This substrate excels in unique SERS activity and large surface area for DNA oligonucleotide modification. As the presence of miR-141, the DNAzyme walker induced cleavage reaction took place on the finely designed and prepared dual DNA conjugated SERS nanoprobes. The SERS nanoprobes can anchor on MCASS by the DNA hybridization that achieved an impressive detection limit in the femtomolar level. SIGNIFICANCE: With this integrated SERS-based microfluidic chip, we provided a miRNA detection strategy using DNAzyme walker amplification technology. It is believed that this strategy could be a powerful tool for miRNA detection and related cancer screening test.

Rapid simultaneous SERS detection of dual myocardial biomarkers on single-track finger-pump microfluidic chip.

Acute myocardial infarction (AMI) is a serious disease with high mortality that afflicts many people around the world. The main cause of death from AMI was the inaccurate early diagnosis, which resulted from the medical treatment might be a delay. Therefore, it is crucial to achieve the rapid detection of AMI. The cardiac troponin I (cTnI) level in human serum may significantly increase as the myocardial membrane ruptured, and the creatine kinase-MB (CK-MB) was also associated with the AMI recurrence and the infarct size of myocardial infarction. Both of them are regarded as important cardiac biomarkers for the early diagnosis of AMI. Therefore, we chose these two cardiac biomarkers as indicators for simultaneous detection. We proposed a single-track finger-pump microfluidic chip for simultaneous surface-enhanced Raman scattering (SERS) detection of cTnI and CK-MB. The entire detection process takes only 5 min without the cumbersome syringe pump. Meanwhile, it enables multiple reagent additions and removals of the unbonded reactants. This microfluidic sensor employed "sandwich" immunoassays based on SERS nanoprobes, AMI biomarkers, and magnetic beads. It is possible to detect two cardiac biomarkers simultaneously in a single measurement, greatly simplifying the detection process and reducing the detection time. Magnetic beads with SERS nanoprobes were separated and captured in the microchamber by a round magnet integrated into the chip. Our results showed that the detection limits of cTnI and CK-MB could reach to 0.01 ng mL-1, respectively. The limit of detections (LODs) match with the clinical threshold values for AMI biomarkers. It is believed that the proposed single-track finger-pump microfluidic chip can be used as an effective tool for determining early AMI.