An integrated microfluidic system for diagnosis of the resistance of Helicobacter pylori to quinolone-based antibiotics

Advances on diagnosis of Helicobacter pylori infections

The association of Helicobacter pylori to several gastric diseases, such as chronic gastritis, peptic ulcer disease, and gastric cancer, and its high prevalence worldwide, raised the necessity to use methods for a proper and fast diagnosis and monitoring the pathogen eradication. Available diagnostic methods can be classified as invasive or non-invasive, and the selection of the best relies on the clinical condition of the patient, as well as on the sensitivity, specificity, and accessibility of the diagnostic test. This review summarises all diagnostic methods currently available, including the invasive methods: endoscopy, histology, culture, and molecular methods, and the rapid urease test (RUT), as well as the non-invasive methods urea breath test (UBT), serological assays, biosensors, and microfluidic devices and the stool antigen test (SAT). Moreover, it lists the diagnostic advantages and limitations, as well as the main advances for each methodology. In the end, research on the development of new diagnostic methods, such as bacteriophage-based H. pylori diagnostic tools, is also discussed.

A 3D-Printed Microfluidic Device for qPCR Detection of Macrolide-Resistant Mutations of Mycoplasma pneumoniae

Mycoplasma pneumonia (MP) is a common respiratory infection generally treated with macrolides, but resistance mutations against macrolides are often detected in mycoplasma pneumoniae in China. Rapid and accurate identification of mycoplasma pneumoniae and its mutant type is necessary for precise medication. This paper presents a 3D-printed microfluidic device to achieve this. By 3D printing, the stereoscopic structures such as microvalves, reservoirs, drainage tubes, and connectors were fabricated in one step. The device integrated commercial polymerase chain reaction (PCR) tubes as PCR chambers. The detection was a sample-to-answer procedure. First, the sample, a PCR mix, and mineral oil were respectively added to the reservoirs on the device. Next, the device automatically mixed the sample with the PCR mix and evenly dispensed the mixed solution and mineral oil into the PCR chambers, which were preloaded with the specified primers and probes. Subsequently, quantitative real-time PCR (qPCR) was carried out with the homemade instrument. Within 80 min, mycoplasma pneumoniae and its mutation type in the clinical samples were determined, which was verified by DNA sequencing. The easy-to-make and easy-to-use device provides a rapid and integrated detection approach for pathogens and antibiotic resistance mutations, which is urgently needed on the infection scene and in hospital emergency departments.

A microfluidic chip for visual investigation of the interaction of nanoemulsion of Satureja Khuzistanica essential oil and a model gram-negative bacteria

Nanotechnology has provided novel approaches against food born and pathogenic bacteria. Within the present study, the effects of pure and nanoemulsified essential oil derived from Satureja Khuzistanica essential oil (SKEO) on Escherichia coli (E. coli ATCC 25922) as a human pathogen has been studied using a microfluidic chip. The morphology and antibacterial activity of E. coli at disparate residence durations (from 2 to 30 min) and various nanoemulsified or pure essential oil concentrations (8.0-62.5 μg mL^-1) and numerous nanoemulsion's droplet sizes from 32 to 124 nm, have been investigated in the microfluidic system. Also, the quantitative analysis including optical density, time killing assay, protein, nucleic acid and potassium release were employed to confirm the effects of bacterial inhibition taking advantage of the chip apparatus. It was revealed that the prepared nanoemulsion left a considerable destructive effect on E. coli bacterial membrane, confirmed by fast release of cytoplasmic elements including protein, nucleic acid and potassium. However, this process was remarkably intensified for both nanoemulsion and pure essential oil using the microfluidic chip versus the conventional methods. The results also revealed that after 4 min of bacterium treatment by 12.5 μg mL^-1 nanoemulsion with 32 nm mean particle size, the bacterial membrane wall began to degrade rapidly, and bacterial activity was almost completely inhibited in a 20-min period. These findings may have implications in the similarly structured and phospholipid-encapsulated bacteria and viruses, like COVID-19.

Advances in diagnosis of Helicobacter pylori through biosensors: Point of care devices

Invasive as well as non-invasive conventional techniques for the detection of Helicobacter pylori (H. pylori) have several limitations that are being overcome by the development of novel, rapid and reliable biosensors. Herein, we describe several biosensors fabricated for the detection of H. pylori. This review aims to provide the principles of biosensors and their components including in the context to H. pylori detection. The major biorecognition elements in H. pylori detection include antigen/antibodies, oligonucleotides and enzymes. Furthermore, the review describes the transducers, such as electrochemical, optical and piezoelectric, also including microfluidics approaches. An overview of the biomarkers associated with H. pylori pathogenesis is also discussed. Finally, the prospects of advancement and commercialization of point-of-care tools are summarized.

A Microfluidic Chip-Based MRS Immunosensor for Biomarker Detection via Enzyme-Mediated Nanoparticle Assembly

Conventional immunoassay methods have their common defects, such as tedious processing steps and inadequate sensitivity, in detecting whole blood. To overcome the above problems, we report a microfluidic chip-based magnetic relaxation switching (MRS) immunosensor via enzyme-mediated nanoparticles to simplify operation and amplify the signal in detecting whole blood samples. In the silver mirror reaction with catalase (CAT) as the catalyst, H2O2 can effectively control the production of Ag NPs. The amount of Ag NPs formed further affects the degree of aggregation of magnetic nanoparticles (MNPS), which gives rise to the changes of transverse relaxation time (T2). Both sample addition and reagent reaction are carried out in the microfluidic chip, thereby saving time and reagent consumption. We also successfully apply the sensor to detect alpha-fetoprotein (AFP) in real samples with a satisfied limit of detection (LOD = 0.56 ng/ml), which is superior to the conventional ELISA.

Rapid quantitative detection of chloramphenicol in milk by microfluidic immunoassay

Chloramphenicol (CAP) is a toxic substance for human health, and detection of CAP residues in milk is necessary. However, most of the traditional CAP detection methods including high performance liquid chromatography-tandem mass spectrometry (HPLC-MS) and enzyme-linked immunosorbent assay (ELISA) are time-consuming and complicated. Herein, an automated microfluidics system for CAP detection in milk was developed. The residual CAP of multiple milk samples was quantitatively detected via competitive immunoassay in a single microfluidic chip simultaneously and automatically, and the reliability of the method was confirmed by flow cytometry. Completion of the detection by the system required less than 20 min and the cost for the detection of ten samples was about US$2.5. The limit of detection was 0.05 µg L^-1, and the recovery rate of CAP in milk ranged from 91.3% to 105.5%. The microfluidic system developed in this study exhibited considerable potential in the point-of-care testing (POCT) of CAP in milk.

One-Step Nucleic Acid Purification and Noise-Resistant Polymerase Chain Reaction by Electrokinetic Concentration for Ultralow-Abundance Nucleic Acid Detection

Nucleic acid amplification tests (NAATs)integrated on a chip hold great promise for point-of-care diagnostics. Currently, nucleic acid (NA) purification remains time-consuming and labor-intensive, and it takes extensive efforts to optimize the amplification chemistry. Using selective electrokinetic concentration, we report one-step, liquid-phase NA purification that is simpler and faster than conventional solid-phase extraction. By further re-concentrating NAs and performing polymerase chain reaction (PCR) in a microfluidic chamber, our platform suppresses non-specific amplification caused by non-optimal PCR designs. We achieved the detection of 5 copies of M. tuberculosis genomic DNA (equaling 0.3 cell) in real biofluids using both optimized and non-optimal PCR designs, which is 10- and 1000-fold fewer than those of the standard bench-top method, respectively. By simplifying the workflow and shortening the development cycle of NAATs, our platform may find use in point-of-care diagnosis.

Microfluidic-Based Nucleic Acid Amplification Systems in Microbiology

Rapid, sensitive, and selective bacterial detection is a hot topic, because the progress in this research area has had a broad range of applications. Novel and innovative strategies for detection and identification of bacterial nucleic acids are important for practical applications. Microfluidics is an emerging technology that only requires small amounts of liquid samples. Microfluidic devices allow for rapid advances in microbiology, enabling access to methods of amplifying nucleic acid molecules and overcoming difficulties faced by conventional. In this review, we summarize the recent progress in microfluidics-based polymerase chain reaction devices for the detection of nucleic acid biomarkers. The paper also discusses the recent development of isothermal nucleic acid amplification and droplet-based microfluidics devices. We discuss recent microfluidic techniques for sample preparation prior to the amplification process.

Anti-Helicobacter pylori and Anti-Inflammatory Effects and Constituent Analysis of Modified Xiaochaihutang for the Treatment of Chronic Gastritis and Gastric Ulcer

Chronic gastritis and gastric ulcers are prevalent throughout the world and are considered to be a global health problem. Modified Xiaochaihutang (MXCHT) prescription is broadly used in traditional medicine hospital for the treatment of gastritis. In order to assess the anti-Helicobacter pylori (H. pylori) effect of MXCHT, agar diffusion method in vitro and fluid dilution method for the minimal inhibitory concentration (MIC) were established. The anti-inflammatory effects were then evaluated using mouse ear edema model and rat paw edema model. The ethanol-induced gastric ulcer method was employed to verify the gastroprotective effect of active extracts in MXCHT. HPLC-TOF-MS/MS was used for analyzing the possible active constituents after oral administration of effective extracts in ethanol-induced gastric ulcer models. MXCHT and 4 different extracts of the bacterial inhibition diameter and MIC were dramatically decreased compared with control group, showing anti-Helicobacter pylori effects. High dose groups of MXCHT, water extract, EtOAc extract, and n-BuOH extract displayed significant anti-inflammatory effects in xylene-induced mouse ear edema model and carrageenan-induced rat paw edema model test. MXCHT and all active extracts exhibited gastroprotective activity and prevented gastric lesions induced by ethanol in rats. 4 prototype components and 4 metabolites were identified after oral administration of EtOAc extract. In addition, 6 prototype components and 6 metabolites were identified in n-BuOH extract. MXCHT, EtOAc extract, and n-BuOH extract demonstrate gastroprotective effects through anti-Helicobacter pylori and anti-inflammatory activities. Thus, this prescription may be a suitable natural source for the prevention and treatment of chronic gastritis and gastric ulcers.

Antibiotic resistance in Helicobacter pylori

PURPOSE OF REVIEW

Treatment of Helicobacter pylori is difficult nowadays because of its high resistance. The prevalence and mechanism of resistance, the different methods to detect it and the clinical implication of resistance were addressed in several research papers last year.

RECENT FINDINGS

Clarithromycin-resistant H. pylori has been recognized by the WHO as 'high priority', for which new antibiotics are needed. Moreover, the Maastricht consensus recommended, in areas with high resistance, that susceptibility tests should be performed, at least after a treatment failure.

SUMMARY

Metronidazole and clarithromycin resistance rates are alarming although they vary among populations. Tetracycline and amoxicillin-resistance are very low in most countries. H. pylori resistance can be detected by phenotypic or by molecular methods. Different break points may be used when performing an antimicrobial susceptibility test, so comparing resistance among different populations is challenging. Genomic techniques open new possibilities in the diagnosis of H. pylori, and the detection of H. pylori and its antimicrobial resistance in faeces is an interesting approach. Eradication rates are dependent on the susceptibility of the strain to metronidazole and clarithromycin, being lower in patients infected with a resistant strain.

Resistance mechanisms of Helicobacter pylori and its dual target precise therapy

Helicobacter pylori drug resistance presents a significant challenge to the successful eradication of this pathogen. To find strategies to improve the eradication efficacy of H. pylori, it is necessary to clarify the resistance mechanisms involved. The mechanisms of H. pylori drug resistance can be investigated from two angles: the pathogen and the host. A comprehensive understanding of the molecular mechanisms of H. pylori resistance based on both pathogen and host would aid the implementation of precise therapy, or ideally "dual target precise therapy" (bacteria and host-specific target therapy). In recent years, with increased understanding of the mechanisms of H. pylori resistance, the focus of eradication has shifted from disease-specific to patient-specific treatment. The implementation of "precision medicine" has also provided a new perspective on the treatment of infectious diseases. In this article, we systematically review current research on H. pylori drug resistance from the perspective of both the pathogen and the host. We also review therapeutic strategies targeted to pathogen and host factors that are aimed at achieving precise treatment of H. pylori.

Diagnosis of Helicobacter pylori infection

Important progress is being made in endoscopic methods which allow clinicians to predict the presence of Helicobacter pylori based on characteristics of gastric mucosa and to obtain targeted biopsies. There are also important developments in molecular methods with various techniques derived from standard PCR, applied both on gastric biopsies and stool specimens. Progress is being made in microfluidic systems to get a reliable diagnosis in a very short time. The interest of the ¹³ C urea breath test has been confirmed as well as stool antigen tests. Attempts are being made to find biological markers of premalignant conditions by serology, other than pepsinogens.

Microfluidics: innovative approaches for rapid diagnosis of antibiotic-resistant bacteria

The emergence of antibiotic-resistant bacteria has become a major global health concern. Rapid and accurate diagnostic strategies to determine the antibiotic susceptibility profile prior to antibiotic prescription and treatment are critical to control drug resistance. The standard diagnostic procedures for the detection of antibiotic-resistant bacteria, which rely mostly on phenotypic characterization, are time consuming, insensitive and often require skilled personnel, making them unsuitable for point-of-care (POC) diagnosis. Various molecular techniques have therefore been implemented to help speed up the process and increase sensitivity. Over the past decade, microfluidic technology has gained great momentum in medical diagnosis as a series of fluid handling steps in a laboratory can be simplified and miniaturized on to a small platform, allowing marked reduction of sample amount, high portability and tremendous possibility for integration with other detection technologies. These advantages render the microfluidic system a great candidate to be developed into an easy-to-use sample-to-answer POC diagnosis suitable for application in remote clinical settings. This review provides an overview of the current development of microfluidic technologies for the nucleic acid based and phenotypic-based detections of antibiotic resistance.

Sensitive detection of Listeria monocytogenes based on highly efficient enrichment with vancomycin-conjugated brush-like magnetic nano-platforms

Pathogens pose a significant threat to public health worldwide. Despite many technological advances in the rapid diagnosis of pathogens, sensitive pathogen detection remains challenging because target pathogenic bacteria usually exist in complex samples at very low concentrations. Here, the construction of multivalent brush-like magnetic nanoprobes and their application for the efficient enriching of pathogens are demonstrated. Brush-like magnetic nanoprobes were constructed by modification with poly-L-lysine (PLL) onto amino-modified magnetic beads, followed by coupling of PEG (amine-PEG₅₀₀₀-COOH) to the amine sites of PLL. Subsequently, vancomycin (Van), a small-molecule antibiotic with affinity to the terminal peptide (D-alanyl-D-alanine) on the cell wall of Gram-positive bacteria, was conjugated to the carboxyl of the PEG. The use of multivalent brush-like magnetic nanoprobes (Van-PEG-PLL-MNPs) results in a high enrichment efficiency (>94%) and satisfactory purity for Listeria monocytogenes (employed as a model) within 20min, even at bacterial concentrations of only 10²cfumL^-1. Integrated with the enrichment of the Van-PEG-PLL-MNP nano-platform and electrochemiluminescence (ECL) detection, Listeria monocytogenes can be rapidly and accurately detected at levels as low as 10cfumL^-1. The approach described herein holds great potential for realizing rapid and sensitive pathogen detection in clinical samples.

One-step immunoassay of C-reactive protein using droplet microfluidics

We present a wash-free high-sensitivity immunoassay of C-reactive proteins with droplet microfluidics. Microbeads are encapsulated within droplets for the immunoassay, and the droplets are scanned by a fluorescence detection platform to quantify the amount of proteins captured on the microbeads. The limit of detection determined by our platform is 0.01 μg mL^-1, which is ten times more sensitive than conventional high-sensitivity C-reactive protein assays. With the decrease in diffusion distance within droplets, the immunoassay requires only half of the time required for similar conventional approaches. This approach for carrying out immunoassays can potentially be applied to other biomarkers beyond C-reactive proteins.

Polymerase chain reaction in microfluidic devices

The invention of the polymerase chain reaction (PCR) has caused a revolution in molecular biology, giving access to a method of amplifying deoxyribonucleic acid (DNA) molecules across several orders of magnitude. Since the first application of PCR in a microfluidic device was developed in 1998, an increasing number of researchers have continued the development of microfluidic PCR systems. In this review, we introduce recent developments in microfluidic-based space and time domain devices as well as discuss various designs integrated with multiple functions for sample preparation and detection. The development of isothermal nucleic acid amplification and digital PCR microfluidic devices within the last five years is also highlighted. Furthermore, we introduce various commercial microfluidic PCR devices.

Integrated microfluidic device using a single universal aptamer to detect multiple types of influenza viruses

DNA aptamers that can bind specific molecular targets have great potential as probes for microbial diagnostic applications. However, aptamers may change their conformation under different operating conditions, thus affecting their affinity and specificity towards the target molecules. In this study, a new integrated microfluidic system was developed that exploited the predictable change in conformation of a single universal influenza aptamer exposed to differing ion concentrations in order to detect multiple types of the influenza virus. Furthermore, the fluorescent-labeled universal aptamer used in this system could distinguish and detect three different influenza viruses (influenza A H1N1, H3N2, and influenza B) at the same time in 20min and therefore has great potential for point-of-care applications requiring rapid diagnosis of influenza viruses.