Volatile organic compounds in headspace characterize isolated bacterial strains independent of growth medium or antibiotic sensitivity.

INTRODUCTION: Early and reliable determination of bacterial strain specificity and antibiotic resistance is critical to improve sepsis treatment. Previous research demonstrated the potential of headspace analysis of volatile organic compounds (VOCs) to differentiate between various microorganisms associated with pulmonary infections in vitro. This study evaluates whether VOC analysis can also discriminate antibiotic sensitive from resistant bacterial strains when cultured on varying growth media. METHODS: Both antibiotic-sensitive and -resistant strains of Pseudomonas aeruginosa, Staphylococcus aureus and Klebsiella pneumonia were cultured on 4 different growth media, i.e. Brain Heart Infusion, Marine Broth, Müller-Hinton and Trypticase Soy Agar. After overnight incubation at 37°C, the headspace air of the cultures was collected on stainless steel desorption tubes and analyzed by gas chromatography time-of-flight mass spectrometry (GC-tof-MS). Statistical analysis was performed using regularized multivariate analysis of variance and cross validation. RESULTS: The three bacterial species could be correctly recognized based on the differential presence of 14 VOCs (p<0.001). This discrimination was not influenced by the different growth media. Interestingly, a clear discrimination could be made between the antibiotic-resistant and -sensitive variant of Pseudomonas aeruginosa (p<0.001) based on their species-specific VOC signature. CONCLUSION: This study demonstrates that isolated microorganisms, including antibiotic-sensitive and -resistant strains of Pseudomonas aeruginosa, could be identified based on their excreted VOCs independent of the applied growth media. These findings suggest that the discriminating volatiles are associated with the microorganisms themselves rather than with their growth medium. This study exemplifies the potential of VOC analysis as diagnostic tool in medical microbiology. However, validation of our results in appropriate in vivo models is critical to improve translation of breath analysis to clinical applications.

A systematic review on the detection of volatile organic compounds in exhaled breath in experimental animals in the context of gastrointestinal and hepatic diseases.

BACKGROUND: Analysis of volatile organic compounds (VOCs) in exhaled breath has the potential to serve as an accurate diagnostic tool for gastro-intestinal diseases. Animal studies could be instrumental as a preclinical base and subsequent clinical translation to humans, as they are easier to standardize and better equipped to relate specific VOCs to metabolic and pathological processes. This review provides an overview of the study design, characteristics and methodological quality of previously published animal studies on analysis of exhaled breath in gastrointestinal and hepatic diseases. Guidelines are provided for standardization in study design and breath collection methods to improve comparability, avoid duplication of research and reduce discomfort of animals in future studies. METHODS: PubMed and Embase database were searched for animal studies using exhaled breath analysis to detect gastro-intestinal diseases. Risk of bias was assessed using the SYRCLE's risk of bias tool for animal studies. Information on study design, standardization methods, animal models, breath collection methods and identified VOCs were extracted from the included studies. RESULTS: 10 studies were included (acute liver failure n = 1, non-alcoholic steatohepatitis n = 1, hepatic ischemia n = 2, mesenteric ischemia n = 2, sepsis and peritonitis n = 3, colitis n = 1). Rats were used in most of the studies. Exhaled breath was mostly collected using invasive procedures as tracheal cannulation or tracheostomy. Poor reporting on standardization, breath collection methods, analytical techniques, as well as heterogeneity of the studies, complicate comparison of the different studies. CONCLUSION: Poor reporting of essential methodological details impaired comprehensive summarizing the various studies on exhaled breath in gastrointestinal and hepatic diseases. Potential pitfalls in study design, and suggestions for improvement of study design are discussed which, when applied, lead to consistent and generalizable results and a reduction in the use of laboratory animals. Refining the methodological quality of animal studies has the potential to improve subsequent clinical trial design.

Characterizing the effects of laser control in laser powder bed fusion on near-surface pore formation via combined analysis of in-situ melt pool monitoring and X-ray computed tomography.

Near-surface or sub-surface pores are critical to the structural integrity of additively manufactured (AM) metal parts, especially in fatigue failure applications. However, their formation in laser powder bed fusion is not well-understood due to the complex processes happening near the surface, which are challenging to monitor. A lack of high-fidelity data hinders understanding of the process and its effects. It is not well-known that problems with laser control parameters such as galvanometer acceleration and laser power on/off delay can form near-surface pores in laser powder bed fusion (LPBF) AM processes, and we investigated the characteristics of these pores in this research. We also demonstrate the capabilities and processes of combined studies using in-situ melt pool images and ex-situ X-ray computed tomography (XCT) images. Using the National Institute of Standards and Technology (NIST) Additive Manufacturing Metrology Testbed (AMMT), varying laser control schemes were implemented while in-situ coaxial melt pool images were acquired during the build of Nickel superalloy parts. A combination of time-stepped digital commands, in-situ coaxial melt pool monitoring images (≈ 8 µm/pixel), and ex-situ high-resolution XCT images (≈ 3.63 µm/voxel) were demonstrated. Advanced image analysis methods were used to characterize the pores found in terms of size and shape distribution and spatial location. XCT images, in high correspondence to melt pool images, clearly show the effects of the laser control parameters. We present the complete analysis chain of AM command, in-situ melt pool imaging, ex-situ XCT acquisition, and image analysis. Possible near-surface pore formation mechanisms are explained through the comparative image analysis. The approach of compiling combined analyses based on time-stepped digital commands, in-situ monitoring results, and ex-situ XCT measurement through image analysis enables observation and categorization of the different near-surface pore formation mechanisms stemming from laser and scan control.

Applying the electronic nose for pre-operative SARS-CoV-2 screening.

BACKGROUND: Infection with SARS-CoV-2 causes corona virus disease (COVID-19). The most standard diagnostic method is reverse transcription-polymerase chain reaction (RT-PCR) on a nasopharyngeal and/or an oropharyngeal swab. The high occurrence of false-negative results due to the non-presence of SARS-CoV-2 in the oropharyngeal environment renders this sampling method not ideal. Therefore, a new sampling device is desirable. This proof-of-principle study investigated the possibility to train machine-learning classifiers with an electronic nose (Aeonose) to differentiate between COVID-19-positive and negative persons based on volatile organic compounds (VOCs) analysis. METHODS: Between April and June 2020, participants were invited for breath analysis when a swab for RT-PCR was collected. If the RT-PCR resulted negative, the presence of SARS-CoV-2-specific antibodies was checked to confirm the negative result. All participants breathed through the Aeonose for five minutes. This device contains metal-oxide sensors that change in conductivity upon reaction with VOCs in exhaled breath. These conductivity changes are input data for machine learning and used for pattern recognition. The result is a value between - 1 and + 1, indicating the infection probability. RESULTS: 219 participants were included, 57 of which COVID-19 positive. A sensitivity of 0.86 and a negative predictive value (NPV) of 0.92 were found. Adding clinical variables to machine-learning classifier via multivariate logistic regression analysis, the NPV improved to 0.96. CONCLUSIONS: The Aeonose can distinguish COVID-19 positive from negative participants based on VOC patterns in exhaled breath with a high NPV. The Aeonose might be a promising, non-invasive, and low-cost triage tool for excluding SARS-CoV-2 infection in patients elected for surgery.

Smoking regular and low-nicotine cigarettes results in comparable levels of volatile organic compounds in blood and exhaled breath.

Smokers are exposed to more than 6000 (toxic) smoke components including volatile organic compounds (VOCs). In this study VOCs levels in headspace of blood and exhaled breath, in the mainstream smoke of three types of cigarettes of one brand varying in declared tar, nicotine and carbon monoxide (TNCO) yields are investigated. The objective was to identify whether VOC levels correlate with TNCO yields of cigarettes smoked according to ISO 3308. Our data show that smoking regular and low-TNCO cigarettes result in comparable levels of VOCs in blood and exhaled breath. Hence, declared TNCO-yields as determined with the ISO 3308 machine smoking protocol are irrelevant for predicting VOC exposure upon human smoking. Venous blood and exhaled breath were sampled from 12 male volunteers directly before and 10 min after smoking cigarettes on 3 d (day 1 Marlboro Red (regular), day 2 Marlboro Prime (highly ventilated, low-TNCO), day 3 Marlboro Prime with blocked filter ventilation (taped)). Upon smoking, the levels of toluene, ethylbenzene, m/p-xylene, o-xylene, and 2,5-dimethylfuran in both headspace of venous blood and exhaled breath increase within the same range for all three cigarette types smoked. However, no strong correlation was found between VOC levels in exhaled breath and VOC levels in headspace of blood because of variations between the individual smoking volunteers. More research is required in order to use exhaled breath sampling as a non-invasive quantitative marker for volatile toxicants from cigarette smoke exposure of different brands.

Investigation of the Effect of Artificial Internal Defects on the Tensile Behavior of Laser Powder Bed Fusion 17-4 Stainless Steel Samples: Simultaneous Tensile Testing and X-Ray Computed Tomography.

Insufficient data are available to fully understand the effects of metal additive manufacturing (AM) defects for widespread adoption of the emerging technology. Characterization of failure processes of complex internal geometries and defects in metal AM can significantly enhance this understanding. We aim to demonstrate a complete experimental measurement process and failure analysis method to study the effects of AM defects. We utilized simultaneous implementation of tensile tests with high-resolution X-ray computed tomography (XCT) measurements on 17-4 stainless steel dog-bone samples with an intentional octahedron-shaped internal cavity included in the gauge length and also containing much smaller lack-of-fusion (LOF) defects, all generated by a Laser Powder Bed Fusion (LPBF) additive manufacturing process. The LOF defects were introduced by intentionally changing the LPBF default processing parameters. XCT image-based linear elastic finite element (FE) simulations were used to interpret the data. The in-situ tensile tests combined with simultaneous XCT measurements revealed the details of the failure process initiated by additively manufactured rough internal surfaces and porous defect structures, which experienced high stress concentrations. Progressive collapse of ligaments leading to larger pores was clearly observed, and the resulting porosity evolution until failure was quantitatively analyzed. The high stress concentrations were also directly confirmed by the FE simulations. The experimental methods described in this paper enable the quantitative study of the complex failure mechanisms of additively manufactured metal parts, and the image-based FE simulation method is effective for identifying and/or confirming possible failure locations and features.

Reducing seroma formation and its sequelae after mastectomy by closure of the dead space: The interim analysis of a multi-center, double-blind randomized controlled trial (SAM trial).

OBJECTIVE: The main objective of this double-blind randomized controlled trial (RCT) was to assess seroma formation and its sequelae in patients undergoing mastectomy. Patients were randomized into one of three groups in which different wound closure techniques were applied: 1) conventional wound closure without flap fixation (CON) 2) flap fixation using sutures (FF-S) and 3) flap fixation using an adhesive tissue glue (FF-G). BACKGROUND: Seroma formation is still a bothersome complication after mastectomy. Flap fixation seems promising in reducing seroma formation. Various flap fixation techniques remain to be analyzed, including long-term outcome measures. METHODS: This trial was conducted in three different hospitals between June 2014 and November 2016. Patients were allocated to one of three groups. The primary outcome was the number of seroma needle aspirations. Secondary outcomes were (surgical site) infections, number of outpatient clinic visits, shoulder function, postoperative pain, patient-reported cosmesis and skin dimpling. RESULTS: A total of 187 patients were randomly assigned to CON (n = 61), FF-S (n = 64) and FF-G (n = 62). The number of seroma aspirations was significantly higher in CON when compared to both flap fixation groups (p = 0.032), with no difference between FF-S and FF-G. Secondary outcomes showed no statistical differences between all groups. The higher number of outpatient clinic visits in CON was considered to be of clinical importance (CON = 27 (44.3%), FF-S = 19 (30.6%) and FF-G = 21 (34.4%)). CONCLUSIONS: Mastectomy followed by flap fixation with either sutures or adhesive tissue glue reduces the number of seroma aspirations when compared to simple wound closure.

Investigation of pore structure in cobalt chrome additively manufactured parts using X-ray computed tomography and three-dimensional image analysis.

Pore structures of additively manufactured metal parts were investigated with X-ray Computed Tomography (XCT). Disks made of a cobalt-chrome alloy were produced using laser-based powder bed fusion (PBF) processes. The additive manufacturing processing parameters (scan speed and hatch spacing) were varied in order to have porosities varying from 0.1% to 70% so as to see the effects of processing parameters on the formation of pores and cracks. The XCT images directly show three-dimensional (3D) pore structure, along with cracks. Qualitative visualization is useful; however, quantitative results depend on accurately segmenting the XCT images. Methods of segmentation and image analysis were carefully developed based, as much as possible, on aspects of the images themselves. These enabled quantitative measures of porosity, including how porosity varies in and across the build direction, pore size distribution, how pore structure varies between parts with similar porosity levels but different processing parameters, pore shape, and particle size distribution of un-melted powder trapped in pores. These methods could possibly serve as the basis for standard segmentation and image analysis methods for metallic additively manufactured parts, enabling accurate and reliable defect detection and quantitative measures of pore structure, which are critical aspects of qualification and certification.

Synchrotron 4-dimensional imaging of two-phase flow through porous media.

Near real-time visualization of complex two-phase flow in a porous medium was demonstrated with dynamic 4-dimensional (4D) (3D + time) imaging at the 2-BM beam line of the Advanced Photon Source (APS) at Argonne National Laboratory. Advancing fluid fronts through tortuous flow paths and their interactions with sand grains were clearly captured, and formations of air bubbles and capillary bridges were visualized. The intense X-ray photon flux of the synchrotron facility made 4D imaging possible, capturing the dynamic evolution of both solid and fluid phases. Computed Tomography (CT) scans were collected every 12 s with a pixel size of 3.25 µm. The experiment was carried out to improve understanding of the physics associated with two-phase flow. The results provide a source of validation data for numerical simulation codes such as Lattice-Boltzmann, which are used to model multi-phase flow through porous media.

The utility of video-assisted thoracic surgery in the diagnosis of pulmonary metastases from renal cell carcinoma.

The definitive diagnosis of pulmonary metastases requires histologic confirmation. Traditional methods of obtaining tissue for histologic review include transbronchial approaches, percutaneous transthoracic needle biopsy, and open lung biopsy. The purpose of this study is to identify the most effective methods of obtaining histologic confirmation of pulmonary metastases. The utility of video-assisted thoracic surgery in diagnosing pulmonary metastases is demonstrated in 2 patients with metastatic renal cell carcinoma. The diagnostic yields and complication rates of transbronchial approaches, percutaneous needle biopsy, open lung biopsy, and video-assisted thoracic surgery are compared. Finally, an algorithm for the evaluation of pulmonary lesions is presented.

Rhabdomyolysis and acute renal failure following radical perineal prostatectomy.

Rhabdomyolysis and acute renal failure can be a rare but serious complication resulting from compromising operative positions following some urologic and gynecologic procedures. We report a lethal case of rhabdomyolysis following radical perineal prostatectomy. The possibility of this complication must be considered prior to performing any operation in the exaggerated lithotomy position. Prevention, early diagnosis, and aggressive treatment are the keys to a successful recovery.