Interference Disturbance Analysis Enables Single-Cell Level Growth and Mobility Characterization for Rapid Antimicrobial Susceptibility Testing

Low-cost, real-time detection of bacterial growth via diffraction-based sensing

The emergence of antibacterial resistance impacts healthcare networks globally, with mortality rates and linked burdens of infection disproportionately affecting the developing world. Rapid alternatives to antibiotic susceptibility testing (AST) allow for swifter, more effective treatment, though they are limited in use in low-resource settings due to significant cost barriers. Herein we demonstrate a simple, cost-effective diffraction sensing-based approach for rapidly detecting bacterial growth (a precursor to AST). Diffraction gratings (1D, lined) directly comprised of our test bacteria (Escherichia coli DH5α) were produced using soft agar-based gel templates designed to direct bacterial attachment and produce a near-zero background signal. The diffraction spot intensities from the live bacterial gratings were monitored in growth and no growth (ampicillin) conditions at room temperature, using a simple fixed laser and photodetector setup. Growth-induced differences in signal were observed within 10-20 minutes, highlighting the sensitivity of this approach and its potential to be adapted as a rapid and accessible AST alternative.

Accurate Prediction of Antimicrobial Susceptibility for Point-of-Care Testing of Urine in Less than 90 Minutes via iPRISM Cassettes

The extensive and improper use of antibiotics has led to a dramatic increase in the frequency of antibiotic resistance among human pathogens, complicating infectious disease treatments. In this work, a method for rapid antimicrobial susceptibility testing (AST) is presented using microstructured silicon diffraction gratings integrated into prototype devices, which enhance bacteria-surface interactions and promote bacterial colonization. The silicon microstructures act also as optical sensors for monitoring bacterial growth upon exposure to antibiotics in a real-time and label-free manner via intensity-based phase-shift reflectometric interference spectroscopic measurements (iPRISM). Rapid AST using clinical isolates of Escherichia coli (E. coli) from urine is established and the assay is applied directly on unprocessed urine samples from urinary tract infection patients. When coupled with a machine learning algorithm trained on clinical samples, the iPRISM AST is able to predict the resistance or susceptibility of a new clinical sample with an Area Under the Receiver Operating Characteristic curve (AUC) of ∼ 0.85 in 1 h, and AUC > 0.9 in 90 min, when compared to state-of-the-art automated AST methods used in the clinic while being an order of magnitude faster.

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.

Antimicrobial Susceptibility Testing in a Rapid Single Test via an Egg-like Multivolume Microchamber-Based Microfluidic Platform

Fast determination of antimicrobial agents' effectiveness (susceptibility/resistance pattern) is an essential diagnostic step for treating bacterial infections and stopping world-wide outbreaks. Here, we report an egg-like multivolume microchamber-based microfluidic (EL-MVM²) platform, which is used to produce a wide range of gradient-based antibiotic concentrations quickly (∼10 min). The EL-MVM² platform works based upon testing a bacterial suspension in multivolume microchambers (microchamber sizes that range from a volume of 12.56 to 153.86 nL). Antibiotic molecules from a stock solution diffuse into the microchambers of various volumes at the same loading rate, leading to different concentrations among the microchambers. Therefore, we can quickly and easily produce a robust antibiotic gradient-based concentration profile. The EL-MVM² platform's diffusion (loading) pattern was investigated for different antibiotic drugs using both computational fluid dynamics simulations and experimental approaches. With an easy-to-follow protocol for sample loading and operation, the EL-MVM² platform was also found to be of high precision with respect to predicting the susceptibility/resistance outcome (>97%; surpassing the FDA-approval criterion for technology-based antimicrobial susceptibility testing instruments). These features indicate that the EL-MVM² is an effective, time-saving, and precise alternative to conventional antibiotic susceptibility testing platforms currently being used in clinical diagnostics and point-of-care settings.

Picoliter droplet array based on bioinspired microholes for in situ single-cell analysis

The division of aqueous samples into microdroplet arrays has many applications in biochemical and medical analysis. Inspired by biological features, we propose a method to produce picoliter droplet arrays for single-cell analysis based on physical structure and interface. A 0.9 pL droplet array with an RSD (relative standard deviation) less than 6.3% and a density of 49,000 droplets/cm² was successfully generated on a PDMS chip (polydimethylsiloxane) from a micromachined glass mold. The droplet generation principle of the wetting behavior in the microholes with splayed sidewalls on the PDMS chip by liquid smearing was exploited. The feasibility of the picoliter droplets for bacterial single-cell analysis was verified by the separation of mixed bacteria into single droplets and isolated in situ bacteria propagation.

Rapid Antimicrobial Susceptibility Testing of Patient Urine Samples Using Large Volume Free-Solution Light Scattering Microscopy

The emergence of antibiotic resistance has prompted the development of rapid antimicrobial susceptibility testing (AST) technologies that will enable evidence-based treatment and promote antimicrobial stewardship. To date, many rapid AST methods have been developed, but few are able to be performed on clinical samples directly. Here we developed a large volume light scattering microscopy technique that tracks phenotypic features of single bacterial cells directly in clinical urine samples without sample enrichment or culturing. The technique demonstrated rapid (90 min) detection of Escherichia coli in 24 clinical urine samples with 100% sensitivity and 83% specificity and rapid (90 min) AST in 12 urine samples with 87.5% categorical agreement with two antibiotics, ampicillin and ciprofloxacin.