Rapid Antibiotic Susceptibility Testing of Uropathogenic E. coli by Tracking Submicron Scale Motion of Single Bacterial Cells

Functional Plasmonic Microscope: Characterizing the Metabolic Activity of Single Cells via Sub-nm Membrane Fluctuations

Metabolic abnormalities are at the center of many diseases, and the capability to film and quantify the metabolic activities of a single cell is important for understanding the heterogeneities in these abnormalities. In this paper, a functional plasmonic microscope (FPM) is used to image and measure metabolic activities without fluorescent labels at a single-cell level. The FPM can accurately image and quantify the subnanometer membrane fluctuations with a spatial resolution of 0.5 μm in real time. These active cell membrane fluctuations are caused by metabolic activities across the cell membrane. A three-dimensional (3D) morphology of the bottom cell membrane was imaged and reconstructed with FPM to illustrate the capability of the microscope for cell membrane characterization. Then, the subnanometer cell membrane fluctuations of single cells were imaged and quantified with the FPM using HeLa cells. Cell metabolic heterogeneity is analyzed based on membrane fluctuations of each individual cell that is exposed to similar environmental conditions. In addition, we demonstrated that the FPM could be used to evaluate the therapeutic responses of metabolic inhibitors (glycolysis pathway inhibitor STF 31) on a single-cell level. The result showed that the metabolic activities significantly decrease over time, but the nature of this response varies, depicting cell heterogeneity. A low-concentration dose showed a reduced fluctuation frequency with consistent fluctuation amplitudes, while the high-concentration dose showcased a decreasing trend in both cases. These results have demonstrated the capabilities of the functional plasmonic microscope to measure and quantify metabolic activities for drug discovery.

A simplified version of rapid susceptibility testing of bacteria and yeasts using optical nanomotion detection

We present a novel optical nanomotion-based rapid antibiotic and antifungal susceptibility test. The technique consisted of studying the effects of antibiotics or antifungals on the nanometric scale displacements of bacteria or yeasts to assess their sensitivity or resistance to drugs. The technique relies on a traditional optical microscope, a video camera, and custom-made image analysis software. It provides reliable results in a time frame of 2-4 h and can be applied to motile, non-motile, fast, and slowly growing microorganisms. Due to its extreme simplicity and low cost, the technique can be easily implemented in laboratories and medical centers in developing countries.

Ultrasensitive bacterial sensing using a disposable all-in-one amperometric platform with self-noise cancellation

The early detection of very low bacterial concentrations is key to minimize the healthcare and safety issues associated with microbial infections, food poisoning or water pollution. In amperometric integrated circuits for electrochemical sensors, flicker noise is still the main bottleneck to achieve ultrasensitive detection with small footprint, cost-effective and ultra-low power instrumentation. Current strategies rely on autozeroing or chopper stabilization causing negative impacts on chip size and power consumption. This work presents a 27-μW potentiostatic-amperometric Delta-Sigma modulator able to cancel its own flicker noise and provide a 4-fold improvement in the limit of detection. The 2.3-mm² all-in-one CMOS integrated circuit is glued to an inkjet-printed electrochemical sensor. Measurements show that the limit of detection is 15 pA_rms, the extended dynamic range reaches 110 dB and linearity is R² = 0.998. The disposable device is able to detect, in less than 1h, live bacterial concentrations as low as 10² CFU/mL from a 50-μL droplet sample, which is equivalent to 5 microorganisms.

Recent advances in surface plasmon resonance imaging and biological applications

Surface Plasmon Resonance Imaging (SPRI) is a robust technique for visualizing refractive index changes, which enables researchers to observe interactions between nanoscale objects in an imaging manner. In the past period, scholars have been attracted by the Prism-Coupled and Non-prism Coupled configurations of SPRI and have published numerous experimental results. This review describes the principle of SPRI and discusses recent developments in Prism-Coupled and Non-prism Coupled SPRI techniques in detail, respectively. And then, major advances in biological applications of SPRI are reviewed, including four sub-fields (cells, viruses, bacteria, exosomes, and biomolecules). The purpose is to briefly summarize the recent advances of SPRI and provide an outlook on the development of SPRI in various fields.

YOLO Algorithm for Long-Term Tracking and Detection of Escherichia Coli at Different Depths of Microchannels Based on Microsphere Positioning Assistance

The effect evaluation of the antibiotic susceptibility test based on bacterial solution is of great significance for clinical diagnosis and prevention of antibiotic abuse. Applying a microfluidic chip as the detection platform, the detection method of using microscopic images to observe bacteria under antibiotic can greatly speed up the detection time, which is more suitable for high-throughput detection. However, due to the influence of the depth of the microchannel, there are multiple layers of bacteria under the focal depth of the microscope, which greatly affects the counting and recognition accuracy and increases the difficulty of relocation of the target bacteria, as well as extracting the characteristics of bacterial liquid changes under the action of antibiotics. After the focal depth of the target bacteria is determined, although the z-axis can be controlled with the help of a three-dimensional micro-operator, the equipment is difficult to operate and the long-term changes of the target bacteria cannot be tracked quickly and accurately. In this paper, the YOLOv5 algorithm is adopted to accurately identify bacteria with different focusing states of multi-layer bacteria at the z-axis with any focal depth. In the meantime, a certain amount of microspheres were mixed into bacteria to assist in locating bacteria, which was convenient for tracking the growth state of bacteria over a long period, and the recognition rates of both bacteria and microspheres were high. The recognition accuracy and counting accuracy of bacteria are 0.734 and 0.714, and the two recognition rates of microspheres are 0.910 and 0.927, respectively, which are much higher than the counting accuracy of 0.142 for bacteria and 0.781 for microspheres with the method of enhanced depth of field (EDF method). Moreover, during long-term bacterial tracking and detection, target bacteria at multiple z-axis focal depth positions can be recorded by the aid of microspheres as a positioning aid for 3D reconstruction, and the focal depth positions can be repositioned within 3-10 h. The structural similarity (SSIM) of microscopic image structure differences at the same focal depth fluctuates between 0.960 and 0.975 at different times, and the root-mean-square error (RMSE) fluctuates between 8 and 12, which indicates that the method also has good relocation accuracy. Thus, this method provides the basis for rapid, high-throughput, and long-term analysis of microscopic changes (e.g., morphology, size) of bacteria detection under the addition of antibiotics with different concentrations based on microfluidic channels in the future.

The Dynamics of Single-Cell Nanomotion Behaviour of Saccharomyces cerevisiae in a Microfluidic Chip for Rapid Antifungal Susceptibility Testing

The fast emergence of multi-resistant pathogenic yeasts is caused by the extensive—and sometimes unnecessary—use of broad-spectrum antimicrobial drugs. To rationalise the use of broad-spectrum antifungals, it is essential to have a rapid and sensitive system to identify the most appropriate drug. Here, we developed a microfluidic chip to apply the recently developed optical nanomotion detection (ONMD) method as a rapid antifungal susceptibility test. The microfluidic chip contains no-flow yeast imaging chambers in which the growth medium can be replaced by an antifungal solution without disturbing the nanomotion of the cells in the imaging chamber. This allows for recording the cellular nanomotion of the same cells at regular time intervals of a few minutes before and throughout the treatment with an antifungal. Hence, the real-time response of individual cells to a killing compound can be quantified. In this way, this killing rate provides a new measure to rapidly assess the susceptibility of a specific antifungal. It also permits the determination of the ratio of antifungal resistant versus sensitive cells in a population.

Progressing Antimicrobial Resistance Sensing Technologies across Human, Animal, and Environmental Health Domains

The spread of antimicrobial resistance (AMR) is a rapidly growing threat to humankind on both regional and global scales. As countries worldwide prepare to embrace a One Health approach to AMR management, which is one that recognizes the interconnectivity between human, animal, and environmental health, increasing attention is being paid to identifying and monitoring key contributing factors and critical control points. Presently, AMR sensing technologies have significantly progressed phenotypic antimicrobial susceptibility testing (AST) and genotypic antimicrobial resistance gene (ARG) detection in human healthcare. For effective AMR management, an evolution of innovative sensing technologies is needed for tackling the unique challenges of interconnected AMR across various and different health domains. This review comprehensively discusses the modern state-of-play for innovative commercial and emerging AMR sensing technologies, including sequencing, microfluidic, and miniaturized point-of-need platforms. With a unique view toward the future of One Health, we also provide our perspectives and outlook on the constantly changing landscape of AMR sensing technologies beyond the human health domain.

Multicolor Coding Up-Conversion Nanoplatform for Rapid Screening of Multiple Foodborne Pathogens

Technologies for rapid screening of multiple foodborne pathogens have been urgently needed because of the complex food matrix and high outbreaks of foodborne diseases. In this study, multicolor coding up-conversion nanoparticles (UCNPs) were synthesized and applied for rapid and simultaneous detection of five kinds of foodborne pathogens. The multicolor coding UCNPs were obtained through doping different concentrations of a sensitizer (Yb³⁺) on the shell of the synthesized NaYF₄:Yb³⁺, Tm³⁺ (20%/2%)@NaYF₄:Yb³⁺, and Er³⁺ (x %/2%) core/shell nanocrystals. All the UCNPs could emit red and green luminescence simultaneously once excited with near-infrared wavelength (980 nm), and the ratio of red and green (R/G ratio) emission light intensity of each kind of UCNPs varied depending on the Yb³⁺ doping concentration. In addition, the magnetic nanoparticles (MNPs) modified with the monoclonal antibodies (mAbs) against the target bacteria were used to capture and separate the bacteria, resulting in obtaining the MNP-bacterium complexes. Different UCNPs with multicolor coding acted as signal probes were also modified with the mAbs to react with the MNP-bacterium complexes to form the MNP-bacterium-UCNP sandwich complexes. After the sandwich complexes were excited with a wavelength of 980 nm, the obtained R/G ratios and the green photoluminescence intensity (PL intensity) could be used to distinguish and quantitatively detect foodborne pathogens, respectively. This proposed nanoplatform could detect five foodborne pathogens simultaneously within 2 h with good sensitivity and specificity, showing great potential for multiplex detection of other targets in the fields of medical diagnosis and food security.

A simple, inexpensive, and rapid method to assess antibiotic effectiveness against exoelectrogenic bacteria

A sufficiently fast and simple antimicrobial susceptibility testing (AST) is urgently required to guide effective antibiotic usages and to surveil the antimicrobial resistance rate. Here, we establish a rapid, quantitative, and high-throughput phenotypic AST by measuring electrons transferred from the interiors of microbial cells to external electrodes. Because the transferred electrons are based on microbial metabolic activities and are inversely proportional to the concentration of potential antibiotics, the changes in electrical outputs can be readily used as a transducing signal to efficiently monitor bacterial growth and antibiotic susceptibility. The sensing is performed by directly measuring the total energy, or all the accumulated microbial electricity, generated by microbial fuel cells (MFCs) arranged in a large-capacity disposable, paper-based testbed. A common Gram-negative pathogenic bacterium Pseudomonas aeruginosa wild-type PAO1 and first-line antibiotic gentamicin (GEN) are used in our experiments. The minimum inhibitory concentration (MIC) values generated from our technique are validated by the gold standard broth microdilution (BMD). Our new approach provides quantitative, actionable MIC results within just 5 h because it measures electricity produced by bacterial metabolism instead of the days needed for growth-observation methods. Moreover, as the equipment needed is simple, common, and inexpensive, our test has immense potential to be adopted in the field or resource-limited hospitals and labs to provide insightful assessments for research and clinical practices.

Single yeast cell nanomotions correlate with cellular activity

Living single yeast cells show a specific cellular motion at the nanometer scale with a magnitude that is proportional to the cellular activity of the cell. We characterized this cellular nanomotion pattern of nonattached single yeast cells using classical optical microscopy. The distribution of the cellular displacements over a short time period is distinct from random motion. The range and shape of such nanomotion displacement distributions change substantially according to the metabolic state of the cell. The analysis of the nanomotion frequency pattern demonstrated that single living yeast cells oscillate at relatively low frequencies of around 2 hertz. The simplicity of the technique should open the way to numerous applications among which antifungal susceptibility tests seem the most straightforward.

A WS2-gold nanoparticle heterostructure-based novel SERS platform for the rapid identification of antibiotic-resistant pathogens

The emergence of antibiotic-resistant bacteria is the biggest threat to our society. The rapid discovery of drug resistant bacteria is very urgently needed to guide antibiotic treatment development. The current manuscript reports the design of a 2D-0D heterostructure-based surface enhanced Raman spectroscopy (SERS) platform, which has the capability for the rapid identification of the multidrug resistant strain of Salmonella DT104. Details of the synthesis and characterization of the heterostructure SERS platform using a two dimensional (2D) WS₂ transition metal dichalcogenide (TMD) and zero dimensional (0D) plasmonic gold nanoparticles (GNPs) have been reported. The current manuscript reveals that the 2D-0D heterostructure-based SERS platform exhibits extremely high Raman enhancement capabilities. Using Rh-6G and 4-ATP probe molecules, we determined that the SERS sensitivity is in the range of ∼10^-10 to 10^-11 M, several orders of magnitude higher than 2D-TMD on its own (10^-3 M) or 0D-GNPs on their own (∼10^-6 to 10^-7 M). Experimental and theoretical finite-difference time-domain (FDTD) simulation data indicate that the synergistic effect of an electromagnetic mechanism (EM) and a chemical mechanism (CM) on the heterostructure is responsible for the excellent SERS enhancement observed. Notably, the experimental data reported here show that the heterostructure-based SERS has the ability to separate a multidrug resistance strain from a normal strain of Salmonella by monitoring the antibiotic-pathogen interaction within 90 minutes, even at a concentration of 100 CFU mL^-1.

Microfluidics as an Emerging Platform for Tackling Antimicrobial Resistance (AMR): A Review

Background:

Antimicrobial resistance (AMR) occurs when microbes become resistant to antibiotics causing complications and limited treatment options. AMR is more significant where antibiotics use is excessive or abusive and the strains of bacteria become resistant to antibiotic treatments. Current technologies for bacteria and its resistant strains identification and antimicrobial susceptibility testing (AST) are mostly central-lab based in hospitals, which normally take days to weeks to get results. These tools and procedures are expensive, laborious and skills based. There is an ever-increasing demand for developing point-of-care (POC) diagnostics tools for rapid and near patient AMR testing. Microfluidics, an important and fundamental technique to develop POC devices, has been utilized to tackle AMR in healthcare. This review mainly focuses on the current development in the field of microfluidics for rapid AMR testing.

Method:

Due to the limitations of conventional AMR techniques, microfluidic-based platforms have been developed for better understandings of bacterial resistance, smart AST and minimum inhibitory concentration (MIC) testing tools and development of new drugs. This review aims to summarize the recent development of AST and MIC testing tools in different formats of microfluidics technology.

Results:

Various microfluidics devices have been developed to combat AMR. Miniaturization and integration of different tools has been attempted to produce handheld or standalone devices for rapid AMR testing using different formats of microfluidics technology such as active microfluidics, droplet microfluidics, paper microfluidics and capillary-driven microfluidics.

Conclusion:

Current conventional AMR detection technologies provide time-consuming, costly, labor-intensive and central lab-based solutions, limiting their applications. Microfluidics has been developed for decades and the technology has emerged as a powerful tool for POC diagnostics of antimicrobial resistance in healthcare providing, simple, robust, cost-effective and portable diagnostics. The success has been reported in research articles; however, the potential of microfluidics technology in tackling AMR has not been fully achieved in clinical settings.

Nanomotion detection based on atomic force microscopy cantilevers

Atomic force microscopes (AFM) or low-noise in-house dedicated devices can highlight nanomotion oscillations. The method consists of attaching the organism of interest onto a silicon-based sensor and following its nano-scale motion as a function of time. The nanometric scale oscillations exerted by biological specimens last as long the organism is viable and reflect the status of the microorganism metabolism upon exposure to different chemical or physical stimuli. During the last couple of years, the nanomotion pattern of several types of bacteria, yeasts and mammalian cells has been determined. This article reviews this technique in details, presents results obtained with dozens of different microorganisms and discusses the potential applications of nanomotion in fundamental research, medical microbiology and space exploration.

Emerging technologies for antibiotic susceptibility testing

Superbugs such as infectious bacteria pose a great threat to humanity due to an increase in bacterial mortality leading to clinical treatment failure, lengthy hospital stay, intravenous therapy and accretion of bacteraemia. These disease-causing bacteria gain resistance to drugs over time which further complicates the treatment. Monitoring of antibiotic resistance is therefore necessary so that bacterial infectious diseases can be diagnosed rapidly. Antimicrobial susceptibility testing (AST) provides valuable information on the efficacy of antibiotic agents and their dosages for treatment against bacterial infections. In clinical laboratories, most widely used AST methods are disk diffusion, gradient diffusion, broth dilution, or commercially available semi-automated systems. Though these methods are cost-effective and accurate, they are time-consuming, labour-intensive, and require skilled manpower. Recently much attention has been on developing rapid AST techniques to avoid misuse of antibiotics and provide effective treatment. In this review, we have discussed emerging engineering AST techniques with special emphasis on phenotypic AST. These techniques include fluorescence imaging along with computational image processing, surface plasmon resonance, Raman spectra, and laser tweezer as well as micro/nanotechnology-based device such as microfluidics, microdroplets, and microchamber. The mechanical and electrical behaviour of single bacterial cell and bacterial suspension for the study of AST is also discussed.

Cell-based biosensors: Recent trends, challenges and future perspectives

Existing at the interface of biology and electronics, living cells have been in use as biorecognition elements (bioreceptors) in biosensors since the early 1970s. They are an interesting choice of bioreceptors as they allow flexibility in determining the sensing strategy, are cheaper than purified enzymes and antibodies and make the fabrication relatively simple and cost-effective. And with advances in the field of synthetic biology, microfluidics and lithography, many exciting developments have been made in the design of cell-based biosensors in the last about five years. 3D cell culture systems integrated with electrodes are now providing new insights into disease pathogenesis and physiology, while cardiomyocyte-integrated microelectrode array (MEA) technology is set to be standardized for the assessment of drug-induced cardiac toxicity. From cell microarrays for high-throughput applications to plasmonic devices for anti-microbial susceptibility testing and advent of microbial fuel cell biosensors, cell-based biosensors have evolved from being mere tools for detection of specific analytes to multi-parametric devices for real time monitoring and assessment. However, despite these advancements, challenges such as regeneration and storage life, heterogeneity in cell populations, high interference and high costs due to accessory instrumentation need to be addressed before the full potential of cell-based biosensors can be realized at a larger scale. This review summarizes results of the studies that have been conducted in the last five years toward the fabrication of cell-based biosensors for different applications with a comprehensive discussion on the challenges, future trends, and potential inputs needed for improving them.

Simultaneous Sensing of Seven Pathogenic Bacteria by Guanidine-Functionalized Upconversion Fluorescent Nanoparticles

The method capable of simultaneously detecting multiple target bacterial pathogens is necessary and of great interest. In this research, we demonstrated our initial effort to simultaneously detect seven common foodborne bacteria by developing a straightforward upconversion fluorescence sensing approach. The fluorescent nanosensor was constructed from a designed guanidine-functionalized upconversion fluorescent nanoparticles (UCNPs@GDN), tannic acid, and hydrogen peroxide (HP) and could quantify pathogenic bacteria in a nonspecific manner because the luminescence of the upconversion fluorescent nanoparticle was effectively strengthened in the presence of bacteria. When the developed nanosensor was applied to quantify multiple bacteria including Escherichia coli, Salmonella, Cronobacter sakazakii, Shigella flexneri, Vibrio parahaemolyticus, Staphylococcus aureus, and Listeria monocytogenes, a linear range of 10³ to 10⁸ cfu mL^-1 and a detection limit of 1.30 × 10² cfu mL^-1 have been obtained for the seven model mixture bacteria. In addition, the similar linear range and detection limit were also obtained for the detection of single bacteria. The present approach also exhibited acceptable recovery values ranging from 70.0 to 118.2% for bacteria in real samples (water, milk, and beef). All these results suggested that the guanidine-functionalized upconversion fluorescent nanosensor could be considered as a promising candidate for the rapid detection and surveillance of microbial pollutants in food and water.

Ultrafast and Ultrasensitive Naked-Eye Detection of Urease-Positive Bacteria with Plasmonic Nanosensors

Identifying the pathogen responsible for an infection is a requirement in order to personalize antimicrobial treatments. Detecting bacterial enzymes, such as proteases, lipases, and oxidoreductases, is a winning approach for detecting pathogens at the point of care. In this Article, a new method for detecting urease-producing bacteria rapidly and at ultralow concentrations is reported. In this method, longsome bacteriological culture steps are substituted for a 10 min capture procedure with positively charged magnetic beads. The presence of urease-positive bacteria on the particles is then queried with a plasmonic signal generation step that generates blue- or red-colored nanoparticle suspensions upon addition of the enzyme substrate. These colorimetric signals, which can be easily identified by eye, are generated by the NH₃-dependent assembly of gold nanoparticles in the presence of bovine serum albumin (BSA). The proposed method can detect Proteus mirabilis with a limit of detection of 10¹ cells mL^-1, with a total assay time of 40 min, even in the presence of a large excess of urease-negative bacteria ( Pseudomonas aeruginosa). Furthermore, it does not require bulky equipment, and it can detect P. mirabilis at clinically relevant concentrations within minutes, making it suitable for detecting urease-positive pathogens at the point of care.

A Rapid Unraveling of the Activity and Antibiotic Susceptibility of Mycobacteria

The development of antibiotic-resistant bacteria is a worldwide health-related emergency that calls for new tools to study the bacterial metabolism and to obtain fast diagnoses. Indeed, the conventional analysis time scale is too long and affects our ability to fight infections. Slowly growing bacteria represent a bigger challenge, since their analysis may require up to months. Among these bacteria, Mycobacterium tuberculosis, the causative agent of tuberculosis, has caused more than 10 million new cases and 1.7 million deaths in 2016 only. We employed a particularly powerful nanomechanical oscillator, the nanomotion sensor, to characterize rapidly and in real time tuberculous and nontuberculous bacterial species, Mycobacterium bovis bacillus Calmette-Guérin and Mycobacterium abscessus, respectively, exposed to different antibiotics. Here, we show how high-speed and high-sensitivity detectors, the nanomotion sensors, can provide a rapid and reliable analysis of different mycobacterial species, obtaining qualitative and quantitative information on their responses to different drugs. This is the first application of the technique to tackle the urgent medical issue of mycobacterial infections, evaluating the dynamic response of bacteria to different antimicrobial families and the role of the replication rate in the resulting nanomotion pattern. In addition to a fast analysis, which could massively benefit patients and the overall health care system, we investigated the real-time responses of the bacteria to extract unique information on the bacterial mechanisms triggered in response to antibacterial pressure, with consequences both at the clinical level and at the microbiological level.

Recent Advances in the Race to Design a Rapid Diagnostic Test for Antimicrobial Resistance

Even with advances in antibiotic therapies, bacterial infections persistently plague society and have amounted to one of the most prevalent issues in healthcare today. Moreover, the improper and excessive administration of antibiotics has led to resistance of many pathogens to prescribed therapies, rendering such antibiotics ineffective against infections. While the identification and detection of bacteria in a patient's sample is critical for point-of-care diagnostics and in a clinical setting, the consequent determination of the correct antibiotic for a patient-tailored therapy is equally crucial. As a result, many recent research efforts have been focused on the development of sensors and systems that correctly guide a physician to the best antibiotic to prescribe for an infection, which can in turn, significantly reduce the instances of antibiotic resistance and the evolution of bacteria "superbugs." This review details the advantages and shortcomings of the recent advances (focusing from 2016 and onward) made in the developments of antimicrobial susceptibility testing (AST) measurements. Detection of antibiotic resistance by genomic AST techniques relies on the prediction of antibiotic resistance via extracted bacterial DNA content, while phenotypic determinations typically track physiological changes in cells and/or populations exposed to antibiotics. Regardless of the method used for AST, factors such as cost, scalability, and assay time need to be weighed into their design. With all of the expansive innovation in the field, which technology and sensing systems demonstrate the potential to detect antimicrobial resistance in a clinical setting?

Phenotypic antibiotic susceptibility testing of pathogenic bacteria using photonic readout methods: recent achievements and impact

The development of antibiotic resistances in common pathogens is an increasing challenge for therapy of infections and especially severe complications like sepsis. To prevent administration of broad-spectrum and potentially non-effective antibiotics, the susceptibility spectrum of the pathogens underlying the infection has to be determined. Current phenotypic standard methods for antibiotic susceptibility testing (AST) require the isolation of pathogens from the patient and the subsequent culturing in the presence of antibiotics leading to results only after 24-72 h. Since the early initialization of an effective antibiotic therapy is crucial for positive treatment result in severe infections, faster methods of AST are urgently needed. A large number of different assay systems are currently tested for their practicability for fast detection of antibiotic resistance profiles. They can be divided into genotypic ones which detect the presence of certain genes or gene products associated with resistances and phenotypic assays which determine the effect of antibiotics on the pathogens. In this mini-review, we summarize current developments in fast phenotypic tests that use photonic approaches and critically discuss their status. We further outline steps that are required to bring these assays into clinical practice.

Role of the Clinical Microbiology Laboratory in Antimicrobial Stewardship

For adequate antimicrobial stewardship, microbiology needs to move from the laboratory to become physically and verbally amenable to the caregivers of an institution. Herein, we describe the contributions of our microbiology department to the antimicrobial stewardship program of a large teaching hospital as 10 main points ranging from the selection of patients deemed likely to benefit from a fast track approach, to their clinical samples, or the rapid reporting of results via a microbiology hotline, to rapid searches for pathogens and susceptibility testing. These points should serve as guidelines for similar programs designed to decrease the unnecessary use of antimicrobials.

Point Spread Function of Objective-Based Surface Plasmon Resonance Microscopy

Objective-based surface plasmon resonance microscopy (SPRM) is a novel optical imaging technique that can map the spatial distribution of a local refractive index based on propagating surface plasmon polaritons (SPPs). Different from some other optical microscopy that shows a dot-like point spread function (PSF), a nanosized object appears as a wave-like pattern containing parabolic tails in SPRM. The geometrical complexity of the wave-like pattern hampered the quantitative interpretation of the PSF of SPRM. Previous studies have shown that two adjacent rings were obtained in the frequency domain by applying a two-dimensional Fourier transform to such patterns. In the present work, a ring-fitting method was developed to extract geometrical features out of the dual rings and to connect these features with several experimental parameters. It was found that the radius of ring equaled to the wavevector of SPPs. Its orientation revealed the propagation direction of SPPs. The coordinate distance of the center of ring gave the parallel component of the wavevector of the incident light, which was regulated by the incident angle. The ring-broadening factor reflected the propagation length of SPPs in a reciprocal relationship. Systematical and quantitative interpretations in the frequency domain not only advanced the basic understanding on the PSF of SPRM but also opened up the possibility to utilize these frequency-domain features for detection and sensing purposes in future.

Detection of Antibiotics and Evaluation of Antibacterial Activity with Screen-Printed Electrodes

This review provides a brief overview of the fabrication and properties of screen-printed electrodes and details the different opportunities to apply them for the detection of antibiotics, detection of bacteria and antibiotic susceptibility. Among the alternative approaches to costly chromatographic or ELISA methods for antibiotics detection and to lengthy culture methods for bacteria detection, electrochemical biosensors based on screen-printed electrodes present some distinctive advantages. Chemical and (bio)sensors for the detection of antibiotics and assays coupling detection with screen-printed electrodes with immunomagnetic separation are described. With regards to detection of bacteria, the emphasis is placed on applications targeting viable bacterial cells. While the electrochemical sensors and biosensors face many challenges before replacing standard analysis methods, the potential of screen-printed electrodes is increasingly exploited and more applications are anticipated to advance towards commercial analytical tools.

Imaging the chemical activity of single nanoparticles with optical microscopy

Chemical activity of single nanoparticles can be imaged and determined by monitoring the optical signal of each individual during chemical reactions with advanced optical microscopes. It allows for clarifying the functional heterogeneity among individuals, and for uncovering the microscopic reaction mechanisms and kinetics that could otherwise be averaged out in ensemble measurements.