Surface Plasmon Resonance Based Label-Free Detection of Salmonella using DNA Self Assembly

Surface plasmon resonance-based oligonucleotide biosensor for Salmonella Typhi detection

Due to high mortality rates, typhoid fever still is one of the major health problems in the world, particularly in developing countries. The lack of highly specific and sensitive diagnostic tests and the great resemblance of typhoid fever symptoms to other diseases made the false-negative diagnosis a major challenge in typhoid fever management. Hence, we decided to design a Surface Plasmon Resonance (SPR) based biosensor for specific detection of Salmonella typhi through DNA hybridization. The results showed that the 10 nM of the synthetic target sequence, as well as 1 nM of PCR product, were the lowest feasible detected concentrations by the designed biosensor. This genosensor was also found to significantly distinguish the complementary sequence with the accuracy of one base mismatch sequence. The surface of the chip can be regenerated with NaOH solution and used for consecutive diagnosis. Therefore, the function of the designed biosensor indicates its high potential for Salmonella typhi detection practice.

Colorimetric Approach for Nucleic Acid Salmonella spp. Detection: A Systematic Review

Water- and food-related health issues have received a lot of attention recently because food-poisoning bacteria, in particular, are becoming serious threats to human health. Currently, techniques used to detect these bacteria are time-consuming and laborious. To overcome these challenges, the colorimetric strategy is attractive because it provides simple, rapid and accurate sensing for the detection of Salmonella spp. bacteria. The aim of this study is to review the progress regarding the colorimetric method of nucleic acid for Salmonella detection. A literature search was conducted using three databases (PubMed, Scopus and ScienceDirect). Of the 88 studies identified in our search, 15 were included for further analysis. Salmonella bacteria from different species, such as S. Typhimurium, S. Enteritidis, S. Typhi and S. Paratyphi A, were identified using the colorimetric method. The limit of detection (LoD) was evaluated in two types of concentrations, which were colony-forming unit (CFU) and CFU per mL. The majority of the studies used spiked samples (53%) rather than real samples (33%) to determine the LoDs. More research is needed to assess the sensitivity and specificity of colorimetric nucleic acid in bacterial detection, as well as its potential use in routine diagnosis.

Overview of Rapid Detection Methods for Salmonella in Foods: Progress and Challenges

Salmonella contamination in food production and processing is a serious threat to consumer health. More and more rapid detection methods have been proposed to compensate for the inefficiency of traditional bacterial cultures to suppress the high prevalence of Salmonella more efficiently. The contamination of Salmonella in foods can be identified by recognition elements and screened using rapid detection methods with different measurable signals (optical, electrical, etc.). Therefore, the different signal transduction mechanisms and Salmonella recognition elements are the key of the sensitivity, accuracy and specificity for the rapid detection methods. In this review, the bioreceptors for Salmonella were firstly summarized and described, then the current promising Salmonella rapid detection methods in foodstuffs with different signal transduction were objectively summarized and evaluated. Moreover, the challenges faced by these methods in practical monitoring and the development prospect were also emphasized to shed light on a new perspective for the Salmonella rapid detection methods applications.

Performance of Immunodiagnostic Tests for Typhoid Fever: A Systematic Review and Meta-Analysis

Typhoid fever, also known as typhoid, is a life-threatening bacterial infection that remains a global health concern. The infection is associated with a significant morbidity and mortality rate, resulting in an urgent need for specific and rapid detection tests to aid prevention and management of the disease. The present review aims to assess the specificity and sensitivity of the available literature on the immunodiagnostics of typhoid fever. A literature search was conducted using three databases (PubMed, ProQuest and Scopus) and manual searches through the references of identified full texts to retrieve relevant literature published between 1 January 2011 and 31 December 2020. Of the 577 studies identified in our search, 12 were included in further analysis. Lipopolysaccharides (LPS) and hemolysin E (HlyE) were the most frequently studied antigens. The specimens examined in these studies included serum and saliva. Using blood culture as the gold standard, anti-LPS IgA gave the highest sensitivity of 96% (95% CI: 93–99) and specificity of 96% (95% CI: 93–99) for distinguishing between typhoid cases and healthy controls, whereas the combination of anti-LPS and anti-flagellin total IgGAM gave the highest sensitivity of 93% (95% CI: 86–99) and specificity of 95% (95% CI: 89–100) for distinguishing typhoid cases and other febrile infections. A comparably high sensitivity of 92% (95% CI: 86–98) and specificity of 89% (95% CI: 78–100) were shown in testing based on detection of the combination of anti-LPS (IgA and IgM) and anti-HlyE IgG as well as a slightly lower sensitivity of 91% (95% CI: 74–100) in the case of anti-50kDa IgA. Anti-50kDa IgM had the lowest sensitivity of 36% (95% CI: 6–65) against both healthy and febrile controls. The development of a rapid diagnostic test targeting antibodies against lipopolysaccharides combined with flagellin appeared to be a suitable approach for the rapid detection test of typhoid fever. Saliva is added benefit for rapid typhoid diagnosis since it is less invasive. As a result, further studies could be done to develop additional approaches for adopting such samples.

Conjugated polymers – a versatile platform for various photophysical, electrochemical and biomedical applications: a comprehensive review

Tuneable properties of conjugated polymers are attractive for use in multiple domains like optical, electronic and biological applications.

Biosensors for rapid detection of Salmonella in food: A review

Salmonella is one of the main causes of foodborne infectious diseases, posing a serious threat to public health. It can enter the food supply chain at various stages of production, processing, distribution, and marketing. High prevalence of Salmonella necessitates efficient and effective approaches for its identification, detection, and monitoring at an early stage. Because conventional methods based on plate counting and real-time polymerase chain reaction are time-consuming and laborious, novel rapid detection methods are urgently needed for in-field and on-line applications. Biosensors provide many advantages over conventional laboratory assays in terms of sensitivity, specificity, and accuracy, and show superiority in rapid response and potential portability. They are now recognized as promising alternative tools and one of the most on-site applicable and end user-accessible methods for rapid detection. In recent years, we have witnessed a flourishing of studies in the development of robust and elaborate biosensors for detection of Salmonella in food. This review aims to provide a comprehensive overview on Salmonella biosensors by highlighting different signal-transducing mechanisms (optical, electrochemical, piezoelectric, etc.) and critically analyzing its recent trends, particularly in combination with nanomaterials, microfluidics, portable instruments, and smartphones. Furthermore, current challenges are emphasized and future perspectives are discussed.

Laboratory Diagnosis of Paratyphoid Fever: Opportunity of Surface Plasmon Resonance

Paratyphoid fever is caused by the bacterium Salmonellaenterica serovar Paratyphi (A, B and C), and contributes significantly to global disease burden. One of the major challenges in the diagnosis of paratyphoid fever is the lack of a proper gold standard. Given the absence of a licensed vaccine against S. Paratyphi, this diagnostic gap leads to inappropriate antibiotics use, thus, enhancing antimicrobial resistance. In addition, the symptoms of paratyphoid overlap with other infections, including the closely related typhoid fever. Since the development and utilization of a standard, sensitive, and accurate diagnostic method is essential in controlling any disease, this review discusses a new promising approach to aid the diagnosis of paratyphoid fever. This advocated approach is based on the use of surface plasmon resonance (SPR) biosensor and DNA probes to detect specific nucleic acid sequences of S. Paratyphi. We believe that this SPR-based genoassay can be a potent alternative to the current conventional diagnostic methods, and could become a rapid diagnostic tool for paratyphoid fever.

Emerging biosensor platforms for the assessment of water-borne pathogens

Pathogens are key contaminants in water that are responsible for the generation of various water-borne diseases, and include viruses, fungi, bacteria, and protozoan parasites. The pathogenic effects of these species in water depend on their shape, size, composition, and structure. The resulting water-borne diseases are a serious threat to the environment, including to humans and animals, and are directly responsible for environmental deterioration and pollution. The potential presence of these pathogens requires sensitive, powerful, efficient, and ideally real-time monitoring methods for their reproducible quantification. Conventional methods for pathogen detection mainly rely on time-consuming enrichment steps followed by biochemical identification strategies, which require assay times ranging from 24 h to up to a week. However, in recent years, significant efforts have been made towards the development of biosensing technologies enabling rapid and close-to-real-time detection of water-borne pathogens. This review summarizes recent developments in biosensors and sensing systems based on a variety of transducer technologies for water-quality monitoring, with specific focus on rapid pathogen detection.

Opportunities and prospects biosensor technologies for food analysis

Existing developments in the field of biosensor technologies with the possibility of practical application for establishing food safety indicators were considered. The classification of biosensors is described depending on the physical phenomena underlying its work, the essence and examples of specific developments for the determination of microorganisms, heavy metals and antibiotics in food products are presented. Prospects of biosensor technologies in the food industry are estimated.

Optimal Conditions for the Asymmetric Polymerase Chain Reaction for Detecting Food Pathogenic Bacteria Using a Personal SPR Sensor

We have been developing quick and simple system for detecting food-poisoning bacteria using a combination of an asymmetric PCR and a portable surface plasmon resonance (SPR) sensor. The system would be suitable for point-of-care detection of food-poisoning bacteria in the field of food industry. In this study, we established a novel method for quantifying the amplified forward (F) and reverse (R) chains of Staphylococcus aureus separately by high-performance liquid chromatography (HPLC). The concentration of single-stranded DNA amplicon excessively amplified, which is crucial for the system, could be calculated as the difference between those of the F- and R-chains. For the R-chain, a correction based on the F-chain concentration in the sample was used to obtain a more accurate value, because the determination of the R-chain concentration was affected by that of the coexisting F-chain. The concentration values were also determined by fluorescence imaging for electrophoresis gels of amplicons with FITC- or Cy5-conjugated primers, and they were in good agreement with the values by the HPLC. The measured concentration of the single-strand F-chain correlated well with the value of the SPR response against the probe that was a complementary sequence of the F-chain, immobilized on the sensor chip of the SPR sensor.

SI-traceable calibration-free analysis for the active concentration of G2-EPSPS protein using surface plasmon resonance

Active proteins play important roles in the function regulation of human bodies and attract much interest for use in pharmaceuticals and clinical diagnostics. However, the lack of primary methods to analyze active proteins means there is currently no metrology standard for active protein measurement. In recent years, calibration-free concentration analysis (CFCA), which is based on surface plasmon resonance (SPR) technology, has been proposed to determine the active concentration of proteins that have specific binding activity with a binding partner without any higher order standards. The CFCA experiment observes the changes of binding rates at totally different two flow rates and uses the known diffusion coefficient of an analyte to calculate the active concentration of proteins, theoretically required, the binding process have to be under diffusion-limited conditions. Measuring the active concentration of G2-EPSPS protein by CFCA was proposed in this study. This method involves optimization of the regeneration buffer and preparation of chip surfaces for appropriate reaction conditions by immobilizing ligands (G2-EPSPS antibodies) on sensor chips (CM5) via amine coupling. The active concentration of G2-EPSPS was then determined by injection of G2-EPSPS protein samples and running buffer over immobilized and reference chip surfaces at two different flow rates (5 and 100μLmin^-1). The active concentration of G2-EPSPS was obtained after analyzing these sensorgrams with the 1:1 model. Using the determined active concentration of G2-EPSPS, the association, dissociation, and equilibrium constants of G2-EPSPS and its antibody were determined to be 2.18 ± 0.03 × 10⁶M^-1s^-1, 5.79 ± 0.06 ×10^-3s^-1, and 2.65 ± 0.06 × 10^-9M, respectively. The performance of the proposed method was evaluated. The within-day precisions were from 3.26% to 4.59%, and the between-day precision was 8.36%. The recovery rate of the method was from 97.46% to 104.34% in the concentration range of 1.5-8nM. The appropriate concentration range of G2-EPSPS in the proposed method was determined to be 1.5-8nM. The active G2-EPSPS protein concentration determined by our method was only 17.82% of that obtained by isotope dilution mass spectrometry, showing the active protein was only a small part of the total G2-EPSPS protein. The measurement principle of the proposed method can be clearly described by equations and the measurement result can be expressed in SI units. Therefore, the proposed method shows promise to become a primary method for active protein concentration measurement, which can benefit the development of certified reference materials for active proteins.

Prevalence of current patterns and predictive trends of multidrug-resistant Salmonella Typhi in Sudan

Background

Enteric fever has persistence of great impact in Sudanese public health especially during rainy season when the causative agent Salmonella enterica serovar Typhi possesses pan endemic patterns in most regions of Sudan - Khartoum.

Objectives

The present study aims to assess the recent state of antibiotics susceptibility of Salmonella Typhi with special concern to multidrug resistance strains and predict the emergence of new resistant patterns and outbreaks.

Methods

Salmonella Typhi strains were isolated and identified according to the guidelines of the International Standardization Organization and the World Health Organization. The antibiotics susceptibilities were tested using the recommendations of the Clinical Laboratories Standards Institute. Predictions of emerging resistant bacteria patterns and outbreaks in Sudan were done using logistic regression, forecasting linear equations and in silico simulations models.

Results

A total of 124 antibiotics resistant Salmonella Typhi strains categorized in 12 average groups were isolated, different patterns of resistance statistically calculated by (y = ax − b). Minimum bactericidal concentration’s predication of resistance was given the exponential trend (y = n e^x) and the predictive coefficient R² > 0 < 1 are approximately alike. It was assumed that resistant bacteria occurred with a constant rate of antibiotic doses during the whole experimental period. Thus, the number of sensitive bacteria decreases at the same rate as resistant occur following term to the modified predictive model which solved computationally.

Conclusion

This study assesses the prediction of multi-drug resistance among S. Typhi isolates by applying low cost materials and simple statistical methods suitable for the most frequently used antibiotics as typhoid empirical therapy. Therefore, bacterial surveillance systems should be implemented to present data on the aetiology and current antimicrobial drug resistance patterns of community-acquired agents causing outbreaks.

Electronic supplementary material

The online version of this article (10.1186/s12941-017-0247-4) contains supplementary material, which is available to authorized users.

Gene Specific DNA Sensors for Diagnosis of Pathogenic Infections

Gene specific DNA based sensors have potential applications for rapid and real time monitoring of hybridization signal with the target nucleic acid of pathogens. Different types of DNA based sensors and their applications have been studied for rapid and accurate detection of pathogens causing human diseases. These sensors are based on surface plasmon resonance, quantum-dots, molecular beacons, piezoelectric and electrochemical etc. Curbing epidemics at an early stage is one of the massive challenges in healthcare systems. Timely detection of the causative organism may provide a solution to restrain mortality caused by the disease. With the advent of interdisciplinary sciences, bioelectronics has emerged as an effective alternative for disease diagnostics. Gene specific DNA sensors present themselves as cost-effective, sensitive and specific platforms for detection of disease causing pathogens. The mini review explores different transducer based sensors and their potential in diagnosis of acute and chronic diseases.

Nano-materials for use in sensing of salmonella infections: Recent advances

Salmonella infectious diseases spreading every day through food have become a life-threatening problem for millions of people and growing menace to society. Health expert's estimate that the yearly cost of all the food borne diseases is approximately $5-6 billion. Traditional methodologies for salmonella analysis provide high reliability and very low limits of detection. Among them immunoassays and Nucleic acid-based assays provide results within 24h, but they are expensive, tedious and time consuming. So, there is an urgent need for development of rapid, robust and cost-effective alternative technologies for real-time monitoring of salmonella. Several biosensors have been designed and commercialized for detection of this pathogen in food and water. In this overview, we have updated the literature concerning novel biosensing methods such as various optical and electrochemical biosensors and newly developed nano- and micro-scaled and aptamers based biosensors for detection of salmonella pathogen. Furthermore, attention has been focused on the principal concepts, applications, and examples that have been achieved up to diagnose salmonella. In addition, commercial biosensors and foreseeable future trends for onsite detecting salmonella have been summarized.

The Development and Evaluation of a Loop-Mediated Isothermal Amplification Method for the Rapid Detection of Salmonella enterica serovar Typhi

Typhoid fever remains a public health threat in many countries. A positive result in traditional culture is a gold-standard for typhoid diagnosis, but this method is time consuming and not sensitive enough for detection of samples containing a low copy number of the target organism. The availability of the loop-mediated isothermal amplification (LAMP) assay, which offers high speed and simplicity in detection of specific targets, has vastly improved the diagnosis of numerous infectious diseases. However, little research efforts have been made on utilizing this approach for diagnosis of Salmonella enterica serovar Typhi by targeting a single and specific gene. In this study, a LAMP assay for rapid detection of S. Typhi based on a novel marker gene, termed STY2879-LAMP, was established and evaluated with real-time PCR (RT-PCR). The specificity tests showed that STY2879 could be amplified in all S. Typhi strains isolated in different years and regions in China, whereas no amplification was observable in non-typhoidal strains covering 34 Salmonella serotypes and other pathogens causing febrile illness. The detection limit of STY2879-LAMP for S. Typhi was 15 copies/reaction in reference plasmids, 200 CFU/g with simple heat-treatment of DNA extracted from simulated stool samples and 20 CFU/ml with DNA extracted from simulated blood samples, which was 10 fold more sensitive than the parallel RT-PCR control experiment. Furthermore, the sensitivity of STY2879-LAMP and RT-PCR combining the traditional culture enrichment method for simulated stool and blood spiked with lower S. Typhi count during the 10 h enrichment time was also determined. In comparison with LAMP, the positive reaction time for RT-PCR required additional 2-3 h enrichment time for either simulated stool or blood specimens. Therefore, STY2879-LAMP is of practical value in the clinical settings and has a good potential for application in developing regions due to its easy-to-use protocol.

A colorimetric and ultrasensitive immunosensor for one-step pathogen detection via the combination of nanoparticle-triggered signal amplification and magnetic separation

Colorimetric and ultrasensitive immunosensor for one-step pathogen detection via the combination of nanoparticle-triggered signal amplification and magnetic separation.