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Antibiotic resistance is widespread throughout the world and represents a serious health concern. There is an urgent need for the development of novel tools for rapidly distinguishing antibiotic resistant bacteria from susceptible strains. Previous work has demonstrated that differences in antimicrobial susceptibility can be reflected in differences in the profile of volatile organic compounds (VOCs) produced by dissimilar strains. The aim of this study was to investigate the effect of the presence of cephalosporin antibiotics on the VOC profile of extended spectrum beta-lactamase (ESBL) and non-ESBL producing strains of Escherichia coli. In this study, VOCs from strains of Escherichia coli positive and negative for the most commonly encountered ESBL, CTX-M in the presence of cephalosporin antibiotics were assessed using solid-phase microextraction (SPME) coupled with a combined gas chromatography-mass spectrometry/metal oxide sensor (GC-MS/MOS) system. Our proof-of-concept study allowed for distinguishing CTX-M positive and negative bacteria within 2 ​h after the addition of antibiotics. One MOS signal (RT: 22.6) showed a statistically significant three-way interaction (p ​= ​0.033) in addition to significant two-way interactions for culture and additive (p ​= ​0.046) plus time and additive (p ​= ​0.020). There were also significant effects observed for time (p ​= ​0.009), culture (p ​= ​0.030) and additive (p ​= ​0.028). No effects were observed in the MS data. The results of our study showed the potential of VOC analysis using SPME combined with a GC-MS/MOS system for the early detection of CTX-M-producing, antibiotic-resistant E. coli, responsible for urinary tract infections (UTIs). [ABSTRACT FROM AUTHOR]

Dissolved hydrogen (dH 2) is an important parameter in anaerobic digestion (AD) processes, in particular in a two-stage operation mode encompassing separate hydrolytic/acidogenic and methanogenic stages. Then, monitoring of dH 2 as a substrate of hydrogenotrophic methanogenesis is essential to avoid feast and famine conditions. Despite its significance, there is currently a lack of established monitoring systems which are capable of reliably measuring dH 2 concentrations in culture broth. To address this challenge, we propose a novel measurement system, which is based on the membrane-free extraction of hydrogen in an extraction chamber and the subsequent analysis by a metal-oxide (MOX) gas sensor. The response time of the MOX sensor lies in the range of seconds, while the entire measurement process completes within a total processing time of about 70 min). This study explores the measurement performance of the dH 2 sensor in the hydrolytic/acidogenic and methanogenic stage during lab-scale anaerobic digestion. The measurement principle was consistently applied for over three months. During this period, the methanogenic stage was partly sparged with gaseous hydrogen to monitor the dH 2 response afterwards. The dH 2 sensor responded reliably to these and other dynamic changes. Depending on the process conditions, concentrations between < 10 and > 4,000 Pa were detected, corresponding to dH 2 concentrations of < 0.074 to > 30 µmol L−1. The findings demonstrated the importance of dH 2 monitoring and show that it facilitates the control of H 2 addition, thereby preventing both under- and oversupply during methanogenesis. [Display omitted] • Quantification of dissolved hydrogen with metal-oxide sensor. • Measurement range and long-term stability suitable for anaerobic fermentation broth. • Reliable detection of dissolved H 2 concentrations during H 2 feeding. • Insights into microbial uptake of hydrogen in anaerobic culture broth. • Flexible production of biogas and carboxylic acids in two-stage anaerobic digestion. [ABSTRACT FROM AUTHOR]

Abstract: A multisensor platform on plastic foil for environmental monitoring has been produced and its gas sensing performance, investigated. It is an array of conductometric metal-oxide (MOX) and capacitive polymer gas sensors integrated with a resistive platinum thermometer on a polyimide sheet substrate. The feasibility of simultaneous measurement of oxidizing and reducing gases, volatile organic compounds (VOCs), humidity and temperature has been demonstrated. MOX signals comparable with those of the devices realized on ceramic substrates have been obtained. Due to its structure, the platform is very versatile and, by using different sensor configurations and sensing materials, it allows the detection of a broad spectrum of gaseous analytes over wide concentration ranges. From the raw signals, temperature and humidity-corrected gas responses have been inferred which have been used for the calibration of the platform sensors. All the integrated devices were stable and gave reproducible signals for more than two months of operation, even when the MOXs ran continuously at 300°C. The performed investigation proved the device concept viability and the reliability of its practical implementation. [Copyright &y& Elsevier]