Rapid antibiotic susceptibility testing by resazurin using thin film platinum as a bio-electrode

Theoretical Evaluation of Fluorinated Resazurin Derivatives for In Vivo Applications

Primarily owing to the pronounced fluorescence exhibited by its reduced form, resazurin (also known as alamarBlue®) is widely employed as a redox sensor to assess cell viability in in vitrostudies. In an effort to broaden its applicability for in vivo studies, molecular adjustments are necessary to align optical properties with the near-infrared imaging window while preserving redox properties. This study delves into the theoretical characterisation of a set of fluorinated resazurin derivatives proposed by Kachur et al., 2015 examining the influence of fluorination on structural and electrochemical properties. Assuming that the conductor-like polarisable continuum model mimics the solvent effect, the density functional level of theory combining M06-2X/6-311G* was used to calculate the redox potentials. Furthermore, (TD-)DFT calculations were performed with PBE0/def2-TZVP to evaluate nucleophilic characteristics, transition states for fluorination, relative energies, and fluorescence spectra. With the aim of exploring the potential of resazurin fluorinated derivatives as redox sensors tailored for in vivo applications, acid-base properties and partition coefficients were calculated. The theoretical characterisation has demonstrated its potential for designing novel molecules based on fundamental principles.

Effects of antimicrobial photodynamic therapy with photodithazine® on methicillin-resistant Staphylococcus aureus (MRSA): Studies in biofilms and experimental model with Galleria mellonella

Staphylococcus aureus infections are a severe health problem due to the high mortality rate. Conventional treatment of these infections is via the administration of antibiotics. However, its indiscriminate use can select resistant microorganisms. Thus, it is necessary to develop alternatives for antibiotic therapy. Antimicrobial Photodynamic Therapy (aPDT), a therapeutic method that associates a photosensitizer (PS), a light source with adequate wavelength to the PS, interacts with molecular oxygen generating reactive oxygen species responsible for cell inactivation, is a viable alternative. This work aimed to analyze, in vitro and in vivo, the action of aPDT with PS Photodithazine® (PDZ) on the methicillin-resistant S. aureus (MRSA) strain. In the in vitro method, the S. aureus biofilm was incubated with PDZ at 50 and 75 μg.mL-1 for 15 min, adopting the light dose of 25, 50, and 100 J/cm2. In addition, PS interaction, formation of reactive oxygen species (ROS), bacterial metabolism, adhesion, bacterial viability, and biofilm structure were evaluated by scanning electron microscopy. Subsequently, the strain was inoculated into models of Galleria mellonella, and the survival curve, health scale, blood cell analysis, and CFU/mL of S. aureus in the hemolymph were analyzed after aPDT. In the in vitro results, bacterial reduction was observed in the different PDZ concentrations, highlighting the parameters of 75 μg.mL-1 of PDZ and 100 J/cm2. As for in vivo results, aPDT increased survival and stimulated the immune system of G. mellonella infected by S. aureus. aPDT proved effective in both models, demonstrating its potential as an alternative therapy in treating MRSA bacterial infections.

Progress in methods for the detection of viable Escherichia coli

Escherichia coli (E. coli) is a prevalent enteric bacterium and a necessary organism to monitor for food safety and environmental purposes. Developing efficient and specific methods is critical for detecting and monitoring viable E. coli due to its high prevalence. Conventional culture methods are often laborious and time-consuming, and they offer limited capability in detecting potentially harmful viable but non-culturable E. coli in the tested sample, which highlights the need for improved approaches. Hence, there is a growing demand for accurate and sensitive methods to determine the presence of viable E. coli. This paper scrutinizes various methods for detecting viable E. coli, including culture-based methods, molecular methods that target DNAs and RNAs, bacteriophage-based methods, biosensors, and other emerging technologies. The review serves as a guide for researchers seeking additional methodological options and aiding in the development of rapid and precise assays. Moving forward, it is anticipated that methods for detecting E. coli will become more stable and robust, ultimately contributing significantly to the improvement of food safety and public health.

Modulation of redox reactivity of resazurin through host-guest complexation with Cucurbit[n]uril (n = 7, 8)

Resazurin (Alamar Blue, RZ) is a widely utilized fluorescent probe for biological sensing, whose fluorescent intensity can be modulated by changing its redox states; thereby, electrochemical reactivity of RZ is of significance when designing a sensing assay. Herein, we report novel two-way electrochemical reactivity modulation of RZ using host-guest complexation with rigid molecular containers cucurbit[n]uril (CBn, n = 7, 8). The complexation between CBn and RZ is confirmed by 1H NMR measurements and supported by computational simulation, and the binding constants are determined via UV-vis titration. Notably, the voltametric data highlights that the redox reactivity of RZ can be activated or deactivated upon encapsulation by CB8 or CB7, respectively. This two-way reactivity modulation is hypothesized to be mediated by the difference in cavity volume that favors or hinders the approach of water molecules to the encapsulated reaction center during the reduction process. Despite the similar cavity size to CB, molecular containers such as cyclodextrins (CDs) exhibit considerably weaker modulation effects. Our approach can potentially be applied to other redox processes that involve proton transfer, and open new possibilities in supramolecular electrochemistry.

Antibiotic resistance mechanism and diagnosis of common foodborne pathogens based on genotypic and phenotypic biomarkers

The emergence of antibiotic-resistant bacteria due to the overuse or inappropriate use of antibiotics has become a significant public health concern. The agri-food chain, which serves as a vital link between the environment, food, and human, contributes to the large-scale dissemination of antibiotic resistance, posing a concern to both food safety and human health. Identification and evaluation of antibiotic resistance of foodborne bacteria is a crucial priority to avoid antibiotic abuse and ensure food safety. However, the conventional approach for detecting antibiotic resistance heavily relies on culture-based methods, which are laborious and time-consuming. Therefore, there is an urgent need to develop accurate and rapid tools for diagnosing antibiotic resistance in foodborne pathogens. This review aims to provide an overview of the mechanisms of antibiotic resistance at both phenotypic and genetic levels, with a focus on identifying potential biomarkers for diagnosing antibiotic resistance in foodborne pathogens. Furthermore, an overview of advances in the strategies based on the potential biomarkers (antibiotic resistance genes, antibiotic resistance-associated mutations, antibiotic resistance phenotypes) for antibiotic resistance analysis of foodborne pathogens is systematically exhibited. This work aims to provide guidance for the advancement of efficient and accurate diagnostic techniques for antibiotic resistance analysis in the food industry.

Moving microcapillary antibiotic susceptibility testing (mcAST) towards the clinic: unravelling kinetics of detection of uropathogenic E. coli, mass-manufacturing and usability for detection of urinary tract infections in human urine

Innovation in infection based point-of-care (PoC) diagnostics is vital to avoid unnecessary use of antibiotics and the development of antimicrobial resistance. Several groups including our research team have in recent years successfully miniaturised phenotypic antibiotic susceptibility tests (AST) of isolated bacterial strains, providing validation that miniaturised AST can match conventional microbiological methods. Some studies have also shown the feasibility of direct testing (without isolation or purification), specifically for urinary tract infections, paving the way for direct microfluidic AST systems at PoC. As rate of bacteria growth is intrinsically linked to the temperature of incubation, transferring miniaturised AST nearer the patient requires building new capabilities in terms of temperature control at PoC, furthermore widespread clinical use will require mass-manufacturing of microfluidic test strips and direct testing of urine samples. This study shows for the first-time application of microcapillary antibiotic susceptibility testing (mcAST) directly from clinical samples, using minimal equipment and simple liquid handling, and with kinetics of growth recorded using a smartphone camera. A complete PoC-mcAST system was presented and tested using 12 clinical samples sent to a clinical laboratory for microbiological analysis. The test showed 100% accuracy for determining bacteria in urine above the clinical threshold (5 out of 12 positive) and achieved 95% categorical agreement for 5 positive urines tested with 4 antibiotics (nitrofurantoin, ciprofloxacin, trimethoprim and cephalexin) within 6 h compared to the reference standard overnight AST method. A kinetic model is presented for metabolization of resazurin, demonstrating kinetics of degradation of resazurin in microcapillaries follow those observed for a microtiter plate, with time for AST dependent on the initial CFU ml^-1 of uropathogenic bacteria in the urine sample. In addition, we show for the first time that use of air-drying for mass-manufacturing and deposition of AST reagents within the inner surface of mcAST strips matches results obtained with standard AST methods. These results take mcAST a step closer to clinical application, for example as PoC support for antibiotic prescription decisions within a day.

Recent Developments in Electrochemical Sensors for the Detection of Antibiotic-Resistant Bacteria

The development of efficient point-of-care (POC) diagnostic tools for detecting infectious diseases caused by destructive pathogens plays an important role in clinical and environmental monitoring. Nevertheless, evolving complex and inconsistent antibiotic-resistant species mire their drug efficacy. In this regard, substantial effort has been expended to develop electrochemical sensors, which have gained significant interest for advancing POC testing with rapid and accurate detection of resistant bacteria at a low cost compared to conventional phenotype methods. This review concentrates on the recent developments in electrochemical sensing techniques that have been applied to assess the diverse latent antibiotic resistances of pathogenic bacteria. It deliberates the prominence of biorecognition probes and tailor-made nanomaterials used in electrochemical antibiotic susceptibility testing (AST). In addition, the bimodal functional efficacy of nanomaterials that can serve as potential transducer electrodes and the antimicrobial agent was investigated to meet the current requirements in designing sensor module development. In the final section, we discuss the challenges with contemporary AST sensor techniques and extend the key ideas to meet the demands of the next POC electrochemical sensors and antibiotic design modules in the healthcare sector.

Advances in the screening of antimicrobial compounds using electrochemical biosensors: is there room for nanomaterials?

The abusive use of antimicrobial compounds and the associated appearance of antimicrobial resistant strains are a major threat to human health. An improved antimicrobial administration involves a faster diagnosis and detection of resistances. Antimicrobial susceptibility testing (AST) are the reference techniques for this purpose, relying mainly in the use of culture techniques. The long time required for analysis and the lack of reproducibility of these techniques have fostered the development of high-throughput AST methods, including electrochemical biosensors. In this review, recent electrochemical methods used in AST have been revised, with particular attention on those used for the evaluation of new drug candidates. The role of nanomaterials in these biosensing platforms has also been questioned, inferring that it is of minor importance compared to other applications.

Rapid differentiation of antibiotic-susceptible and -resistant bacteria through mediated extracellular electron transfer

Conventional methods for testing antibiotic susceptibility rely on bacterial growth on agar plates (diffusion assays) or in liquid culture (microdilution assays). These time-consuming assays use population growth as a proxy for cellular respiration. Herein we propose to use mediated extracellular electron transfer as a rapid and direct method to classify antibiotic-susceptible and -resistant bacteria. We tested antibiotics with diverse mechanisms of action (ciprofloxacin, imipenem, oxacillin, or tobramycin) with four important nosocomial pathogens (Acinetobacter baumannii, Staphylococcus aureus, Escherichia coli, and Klebsiella pneumoniae) by adding the bacterial culture to a custom-designed electrochemical cell with a glassy-carbon electrode and growth media supplemented with a soluble electron transfer mediator, phenazine methosulfate (PMS). During cell respiration, liberated electrons reduce PMS, which is then oxidized on the electrode surface, and current is recorded. Using this novel approach, we were able to consistently classify strains as antibiotic-resistant or -susceptible in <90 min for methodology development and <150 min for blinded tests.

Electrochemical Sensors for Antibiotic Susceptibility Testing: Strategies and Applications

Increasing awareness of the impacts of infectious diseases has driven the development of advanced techniques for detecting pathogens in clinical and environmental settings. However, this process is hindered by the complexity and variability inherent in antibiotic-resistant species. A great deal of effort has been put into the development of antibiotic-resistance/susceptibility testing (AST) sensors and systems to administer proper drugs for patient-tailored therapy. Electrochemical sensors have garnered increasing attention due to their powerful potential to allow rapid, sensitive, and real-time monitoring, alongside the low-cost production, feasibility of minimization, and easy integration with other techniques. This review focuses on the recent advances in electrochemical sensing strategies that have been used to determine the level of antibiotic resistance/susceptibility of pathogenic bacteria. The recent examples of the current electrochemical AST sensors discussed here are classified into four categories according to what is detected and quantitated: the presence of antibiotic-resistant genes, changes in impedance caused by cell lysis, current response caused by changes in cellular membrane properties, and changes in the redox state of redox molecules. It also discusses potential strategies for the development of electrochemical AST sensors, with the goal of broadening their practical applications across various scientific and technological fields.

A New Colorimetric Method for Rapid Detection of Antibiotic Resistance in Escherichia coli Isolates

Background: The quick diagnosis and early initiation of antibiotic therapy in bacteria-induced infections is of paramount importance. Accordingly, the rapid identification of the causative agent, the short-term results of antibiotic sensitivity, the selection and use of right antibiotics for treatment further highlights the significance of this issue. Objectives: This study aimed to develop a new susceptibility testing method to provide rapid results in Escherichia coli clinical isolates and report the antibiotic susceptibility test results to clinicians in a short period. Methods: In the study, one hundred and ten E. coli clinical isolates were tested. In this regard, antibiotics recommended by the "Clinical and Laboratory Standards Institute (CLSI)" for testing the sensitivity of E. coli isolates, including amoxicillin-clavulanate, cefixime, ceftriaxone, ertapenem, ciprofloxacin, gentamicin, trimethoprim-sulfamethoxazole, and nitrofurantoin were tested. For quality control, E. coli ATCC25922, E. coli ATCC35218, Staphylococcus aureus ATCC29213, and E. coli 13846NTCC strains were used. The broth microdilution method recommended by CLSI was used as the reference method. Minimum inhibitory concentration values were determined, and antimicrobial susceptibilities were then determined according to the “European Committee on Antimicrobial Susceptibility Testing (EUCAST)” criteria. In the next phase, the results of the resazurin microplate method (RMM) were compared. Results: The comparison of the RMM developed in the present study with the reference method revealed that the calculated essential agreement ratios for eight antibiotics varied from 82.72 to 100%, and the categorical agreement values ranged from 95.45 to100%. Conclusions: According to the findings, the RMM results were highly in agreement with the results of the reference method. RMM allows the detection of antibiotic susceptibility quickly (e.g., within 5 hours) as such it is preferred, especially for laboratories with limited facilities. However, further multi-center studies are recommended to use this method in routine laboratories.

Advances in Antimicrobial Resistance Monitoring Using Sensors and Biosensors: A Review

The indiscriminate use and mismanagement of antibiotics over the last eight decades have led to one of the main challenges humanity will have to face in the next twenty years in terms of public health and economy, i.e., antimicrobial resistance. One of the key approaches to tackling antimicrobial resistance is clinical, livestock, and environmental surveillance applying methods capable of effectively identifying antimicrobial non-susceptibility as well as genes that promote resistance. Current clinical laboratory practices involve conventional culture-based antibiotic susceptibility testing (AST) methods, taking over 24 h to find out which medication should be prescribed to treat the infection. Although there are techniques that provide rapid resistance detection, it is necessary to have new tools that are easy to operate, are robust, sensitive, specific, and inexpensive. Chemical sensors and biosensors are devices that could have the necessary characteristics for the rapid diagnosis of resistant microorganisms and could provide crucial information on the choice of antibiotic (or other antimicrobial medicines) to be administered. This review provides an overview on novel biosensing strategies for the phenotypic and genotypic determination of antimicrobial resistance and a perspective on the use of these tools in modern health-care and environmental surveillance.

Rapid antibiotic susceptibility testing using resazurin bulk modified screen-printed electrochemical sensing platforms

Urinary tract infections (UTIs) are one of the most common types of bacterial infection. UTIs can be associated with multidrug resistant bacteria and current methods of determining an effective antibiotic for UTIs can take up to 48 hours, which increases the chances of a negative prognosis for the patient. In this paper we report for the first time, the fabrication of resazurin bulk modified screen-printed macroelectrodes (R-SPEs) demonstrating them to be effective platforms for the electrochemical detection of antibiotic susceptibility in complicated UTIs. Using differential pulse voltammetry (DPV), resazurin was able to be detected down to 15.6 μM. R-SPEs were utilised to conduct antibiotic susceptibility testing (AST) of E. coli (ATCC® 25922) to the antibiotic gentamicin sulphate using DPV to detect the relative concentrations of resazurin between antibiotic treated bacteria, and bacteria without antibiotic treatment. Using R-SPEs, antibiotic susceptibility was determined after a total elapsed time of 90 minutes including the inoculation of the artificial urine, preincubation and testing time. The use of electrochemistry as a phenotypic means of identifying an effective antibiotic to treat a complicated UTI offers a rapid and accurate alternative to culture based methods for AST with R-SPEs offering an inexpensive and simpler alternative to other AST methods utilising electrochemical based approaches.

Rapid and real-time monitoring of bacterial growth against antibiotics in solid growth medium using a contactless planar microwave resonator sensor

Infection diagnosis and antibiotic susceptibility testing (AST) are pertinent clinical microbiology practices that are in dire need of improvement, due to the inadequacy of current standards in early detection of bacterial response to antibiotics and affordability of contemporarily used methods. This paper presents a novel way to conduct AST which hybridizes disk diffusion AST with microwave resonators for rapid, contactless, and non-invasive sensing and monitoring. In this research, the effect of antibiotic (erythromycin) concentrations on test bacterium, Escherichia coli (E. coli) cultured on solid agar medium (MH agar) are monitored through employing a microwave split-ring resonator. A one-port microwave resonator operating at a 1.76 GHz resonant frequency, featuring a 5 mm² sensitive sensing region, was designed and optimized to perform this. Upon introducing uninhibited growth of the bacteria, the sensor measured 0.005 dB/hr, with a maximum change of 0.07 dB over the course of 15 hours. The amplitude change decreased to negligible values to signify inhibited growth of the bacteria at higher concentrations of antibiotics, such as a change of 0.005 dB in resonant amplitude variation while using 45 µg of antibiotic. Moreover, this sensor demonstrated decisive results of antibiotic susceptibility in under 6 hours and shows great promise to expand automation to the intricate AST workflow in clinical settings, while providing rapid, sensitive, and non-invasive detection capabilities.

Efficiency of Antimicrobial Photodynamic Therapy with Photodithazine® on MSSA and MRSA Strains

Staphylococccus aureus is a ubiquitous and opportunistic bacteria associated with high mortality rates. Antimicrobial photodynamic therapy (aPDT) is based on the application of a light source and a photosensitizer that can interact with molecular oxygen, forming Reactive Oxygen Species (ROS) that result in bacterial inactivation. This study aimed to analyze, in vitro, the action of aPDT with Photodithazine^® (PDZ) in methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) strains. The strains were incubated with PDZ at 25, 50, 75, and 100 mg/L for 15 min and irradiated with fluences of 25, 50, and 100 J/cm². The internalization of PDZ was evaluated by confocal microscopy, the bacterial growth by counting the number of colony-forming units, as well as the bacterial metabolic activity post-aPDT and the production of ROS. In both strains, the photosensitizer was internalized; the production of ROS increased when the aPDT was applied; there was a bacterial reduction compared to the control at all the evaluated fluences and concentrations; and, in most parameters, it was obtained complete inactivation with significant difference (p < 0.05). The implementation of aPDT with PDZ in clinical strains of S. aureus has resulted in its complete inactivation, including the MRSA strains.

Rapid Determination of Antibiotic Resistance in Klebsiella pneumoniae by a Novel Antibiotic Susceptibility Testing Method Using SYBR Green I and Propidium Iodide Double Staining

Due to the broad-spectrum antibiotic usage and empirical treatments, the pathogenic bacterium, Klebsiella pneumoniae, has shown extremely high detection rates at hospitals with an increasing antibiotic resistance. Therefore, rapid detection of the antibiotic resistance is urgently required and essential for effective treatments. In this study, we evaluated the performance of a newly developed method for ultra-rapid detection of antibiotic resistance in 30–60 min in K. pneumoniae by using the SYBR Green I and propidium iodide (PI) staining. A total of 100 clinical isolates were tested for antibiotic resistance using four different antibiotics (ceftriaxone, cefepime, meropenem, and ciprofloxacin). The results showed that the SYBR Green I/PI rapid antibiotic susceptibility test (AST) could reliably detect antibiotic resistance to the four drugs in 60 min, and the results were highly concordant with the conventional AST (i.e., Kirby-Bauer method and broth microdilution method) for detection of ceftriaxone, cefepime, meropenem, and ciprofloxacin resistance with a high accuracy of 99, 96, 96, and 93%, respectively. Therefore, the rapid AST established in our study helps to enable targeted therapy to save lives and reduce the empirical use of antibiotics and ultimately the health and economic burdens of antibiotic resistance.

Assessment of bacterial viability by laser desorption ionization mass spectrometry for antimicrobial susceptibility testing

Bacterial infection poses a serious threat to human health worldwide. Rapid antimicrobial susceptibility testing (AST) is essential for the clinical treatment of bacterial infection patients. However, the traditional AST relies on bacteria culture, which is time-consuming and limits the analysis to culturable species. Herein, we present a laser desorption ionization (LDI) mass spectrometry-based method for rapid bacterial viability assessment and AST by tracing the redox of resazurin (RS) by viable bacteria. RS as well as its reduction product, fluorescent resorufin (RF), can be directly detected by LDI-MS in the absence of matrix. The intensity ratio between RF and RS can be used to assess the viability of bacteria in specimens. We have demonstrated the high efficiency of the method using different bacterial species, including K. pneumoniae, S. aureus, E. coli, and P. aeruginosa, and various antibiotic drugs, such as ciprofloxacin, ampicillin, tetracycline, oxytetracycline, ciprofloxacin and levofloxacin. Compared to traditional methods based on optical absorption, the current method is faster and more sensitive. Furthermore, we applied the method to bacterial viability detection and AST using human body fluid samples, i.e. serum and urine, demonstrating that it can screen rapidly appropriate antibiotic drugs for timely clinical treatment of infectious diseases. With the advantages of simplicity in methodology as well as sensitivity and speed in analysis, the current method holds the potential of clinical usages.

Organic redox-active crystalline layers for reagent-free electrochemical antibiotic susceptibility testing (ORACLE-AST)

Rapid antibiotic susceptibility testing (AST) is critical in determining bacterial resistance or susceptibility to a particular antibiotic. Simple-to-use phenotype-based AST platforms can assist care-givers in timely prescription of the right antibiotic. Monitoring the change of bacterial viability by measuring electrochemical Faradaic current is a promising approach for rapid AST. However, the existing works require mixing redox-active reagents in the solution which can interfere with the antibiotics. In this paper, we developed a facile electrodeposition process for creating a redox-active crystalline layer (denoted as RZx) on pyrolytic graphite sheets (PGS), which was then utilized as the sensing layer for reagent-free electrochemical AST. To demonstrate the proof-of-principle, we tested the sensors with Escherichia coli (E. coli) K-12 treated with two antibiotics, ampicillin and kanamycin. While the sensors enable detection of bacterial metabolism mainly due to pH-sensitivity of RZx (∼ 53 mV/pH), secreted redox-active metabolites/compounds from whole cells are likely contributing to the signal as well. By monitoring the differential voltammetric signals, the sensors enable accurate prediction of the minimum inhibitory concentration (MIC) in 60 min (p < 0.03). The sensors are stable after 60 days storage in ambient conditions and enable analysis of microbial viability in complex solutions, as demonstrated in spiked milk and human whole blood.

Comparison of photodynamic therapy with methylene blue associated with ceftriaxone in gram-negative bacteria; an in vitro study

The resistance of microorganisms increases the need for new antimicrobial therapies. The aim of this study was to evaluate the in vitro action of photodynamic therapy and its combination with ceftriaxone in third generation cephalosporin resistant gram-negative bacteria. Clinical strains of Klebsiella pneumoniae, Enterobacter aerogenes and Escherichia coli were obtained, incubated with MB for 15 min combined or not with ceftriaxone and irradiated with fluence of 10 and 25 J/cm². MB internalization was evaluated by confocal microscopy. Cell viability was assessed by counting colony forming units and bacterian metabolism by the resazurin test. MB has been observed within cells, although not in all bacteria. PDT-MB alone and combined with Ceftriaxone reduced bacterial growth by approximately 1 log at 10 J/cm² of fluence and 4 logs by 25 J/cm², with a significant difference from the control group. The reduction in bacterial growth between the treated groups was similar, without significant difference between them. The Resazurin test showed lower bacterial metabolic activity in the treated groups, but it did not allow to observe difference between fluences. It was concluded with this study that the internalization of MB was not observed in all cells of K. pneumoniae, E. aerogenes and E. coli strains. There was less bacterial metabolic activity in the treated groups, with no variation between different fluences. PDT-MB 25 J/cm² alone and combined with Ceftriaxone showed antimicrobial action, but the PDT-MB/Ceftriaxone combination had no potentiating effect.

Exploiting open source 3D printer architecture for laboratory robotics to automate high-throughput time-lapse imaging for analytical microbiology

Growth in open-source hardware designs combined with the low-cost of high performance optoelectronic and robotics components has supported a resurgence of in-house custom lab equipment development. We describe a low cost (below $700), open-source, fully customizable high-throughput imaging system for analytical microbiology applications. The system comprises a Raspberry Pi camera mounted on an aluminium extrusion frame with 3D-printed joints controlled by an Arduino microcontroller running open-source Repetier Host Firmware. The camera position is controlled by simple G-code scripts supplied from a Raspberry Pi singleboard computer and allow customized time-lapse imaging of microdevices over a large imaging area. Open-source OctoPrint software allows remote access and control. This simple yet effective design allows high-throughput microbiology testing in multiple formats including formats for bacterial motility, colony growth, microtitre plates and microfluidic devices termed ‘lab-on-a-comb’ to screen the effects of different culture media components and antibiotics on bacterial growth. The open-source robot design allows customization of the size of the imaging area; the current design has an imaging area of ~420 × 300mm, which allows 29 ‘lab-on-a-comb’ devices to be imaged which is equivalent 3480 individual 1μl samples. The system can also be modified for fluorescence detection using LED and emission filters embedded on the PiCam for more sensitive detection of bacterial growth using fluorescent dyes.