Microscopy of Woven and Nonwoven Face Covering Materials: Implications for Particle Filtration.

A suite of natural, synthetic, and mixed synthetic-natural woven fabrics, along with nonwoven filtration layers from a surgical mask and an N95 respirator, was examined using visible light microscopy, scanning electron microscopy, and micro-X-ray computed tomography (µXCT) to determine the fiber diameter distribution, fabric thickness, and the volume of solid space of the fabrics. Nonwoven materials exhibit a positively skewed distribution of fiber diameters with a mean value of ≈3 µm, whereas woven fabrics exhibit a normal distribution of diameters with mean values roughly five times larger (>15 µm). The mean thickness of the N95 filtration material is 1093 µm and is greater than that of the woven fabrics that span from 420 to 650 µm. A new procedure for measuring the thickness of flannel fabrics is proposed that accounts for raised fibers. µXCT allowed for a quantitative nondestructive approach to measure fabric porosity as well as the surface area/volume. Cotton flannel showed the largest mean isotropy of any fabric, though fiber order within the weave is poorly represented in the surface electron images. Surface fabric isotropy and surface area/volume ratios are proposed as useful microstructural quantities to consider for future particle filtration modeling efforts of woven materials.

The need for ambulatory emergency oncology: exemplified by the management of immune checkpoint inhibitor toxicity.

Cancer patients seeking emergency care can be vulnerable in increasingly overcrowded Emergency Departments and timely delivery of care is often aspirational rather than reality in many acute care systems. Ambulatory emergency care and its various international models are recognized as contributing to the safety and sustainability of emergency care services. This schema can logically be extended to the emergency oncology setting. The recent proliferation of immune checkpoint inhibitors (ICIs) has led to another opportunity for the management of oncologic complications in the ambulatory emergency care setting. More nuanced risk stratification of currently perceived high-risk toxicities may also afford the opportunity to personalize acute management. Virtual wards, which predominantly provide virtual monitoring only, and hospital at home services, which provide more comprehensive in-person assessment and interventions, may be well suited to supporting care for ICI toxicity alongside hospital-based assessment. Emergency management guidelines for immune-mediated toxicities will increasingly need to be both pragmatic and deliverable, especially as larger numbers of patients will present outside cancer centers. Identifying and modelling those suitable for emergency ambulatory care is integral to achieving this.

Selection of Chemotherapy in Advanced Poorly Differentiated Extra-Pulmonary Neuroendocrine Carcinoma.

Extra-pulmonary poorly differentiated neuroendocrine carcinoma is rare, and evidence for treatment has been limited. In this article, the evidence behind the cytotoxic chemotherapy choices used for metastatic or unresectable EP-PD-NEC is reviewed. In the first-line setting, etoposide and platinum chemotherapy or irinotecan and platinum have been demonstrated to be equivalent in a large phase III trial. Questions remain regarding the optimal number of cycles, mode of delivery, and the precise definition of platinum resistance in this setting. In the second-line setting, FOLFIRI has emerged as an option, with randomized phase 2 trials demonstrating modest, but significant, response rates. Beyond this, data are extremely limited, and several regimens have been used. Heterogeneity in biological behaviour is a major barrier to optimal EP-PD-NEC management. Available data support the potential role of the Ki-67 index as a predictive biomarker for chemotherapy response. A more personalised approach to management in future studies will be essential, and comprehensive multi-omic approaches are required to understand tumour somatic genetic changes in relation to their effects on the surrounding microenvironment.

Improved outcomes with early immunosuppression in patients with immune-checkpoint inhibitor induced myasthenia gravis, myocarditis and myositis: a case series.

PURPOSE: Myasthenia gravis (MG) is a rare but life-threatening complication of immune-checkpoint inhibitor (ICI) therapy and often co-presents with myositis and myocarditis. Previous case series of ICI-related MG have reported high mortality rates. We present a series of ten patients from a tertiary oncology centre outlining outcomes of an early multi-modal immunosuppression strategy. METHODS: We reviewed The Christie Hospital database of immunotherapy-related toxicity from 2017 to 2020. Symptom severity was assessed using the Myasthenia Gravis Foundation of America (MGFA) classification. RESULTS: Ten patients with ICI-related MG were identified. All patients presented following 1 (n = 4) or 2 (n = 6) cycles of ICI. Symptom progression was rapid with a median of 3 days from onset of symptoms to admission. Concomitant myositis and myocarditis were observed in nine patients. AChR or MuSK autoantibodies were positive in six patients. All patients received urgent treatment with intravenous methylprednisolone (IVMP) and eight received intravenous immunoglobulin (IVIG). A single patient died from myasthenia-related symptoms; the remaining 9 patients were successfully discharged. CONCLUSION: In our cohort, we demonstrate good outcomes associated with early intensive immunosuppressive treatment with IVIG and IVMP. An agreed national treatment protocol or clinical discussion forum would be beneficial.

Low muscle mass measured at T12 is a prognostic biomarker in unresectable oesophageal cancers receiving chemoradiotherapy.

BACKGROUND AND PURPOSE: Low muscle mass is an imaging biomarker of patient frailty that has been associated with increased toxicity and decreased survival in a number of cancers. Patients with unresectable oesophageal cancer receive chemoradiotherapy as standard of care. Muscle mass is not yet an established prognostic marker in this population. Muscle mass is usually assessed by segmenting skeletal muscle at the L3 vertebral level. But radiotherapy planning scans for oesophageal cancers do not always image this level, which has limited previous studies of body composition. Skeletal muscle is known to regulate immune function, but the association of muscle mass with lymphopenia in cancer patients has not been shown. MATERIALS AND METHODS: We retrospectively analyse 135 oesophageal cancer patients who received chemoradiotherapy and investigate the prognostic value of skeletal muscle area assessed at T12. We also examine the association between muscle mass and radiation-induced lymphopenia. RESULTS: We find that low muscle mass is associated with poorer overall survival (hazard ratio [95% confidence interval]: 0.72 [0.53-0.97]). However, this effect interacts with body mass index (BMI) such that the prognostic value of low muscle mass is removed by high BMI. In our study, patients with low muscle mass were more prone to radiation-induced lymphopenia (75% vs. 50% in patients with high muscle mass). A significant decrease in circulating lymphocytes was associated with poorer overall survival (hazard ratio [95% confidence interval]: 0.68 [0.47-0.99]). CONCLUSION: Our study shows that assessing muscle mass at T12 is feasible and provides prognostic information. Low muscle mass at T12 is associated with poorer overall survival and increased risk of radiation-induced lymphopenia. Muscle mass provides additional information over performance status and BMI. Low BMI patients are most affected by low muscle mass, highlighting the importance of close nutritional support in this population.

The AGAMENON-SEOM model for prediction of survival in patients with advanced HER2-positive oesophagogastric adenocarcinoma receiving first-line trastuzumab-based therapy.

Background: Trastuzumab and chemotherapy is the standard first-line treatment in human epidermal growth factor receptor 2 (HER2)-positive advanced gastro-oesophageal cancer. The objective was to develop a predictive model for overall survival (OS) and progression-free survival (PFS) in patients treated with trastuzumab. Methods: Patients with HER2-positive advanced gastro-oesophageal adenocarcinoma (AGA) from the Spanish Society of Medical Oncology (SEOM)-AGAMENON registry and treated first line with trastuzumab and chemotherapy between 2008 and 2021 were included. The model was externally validated in an independent series (The Christie NHS Foundation Trust, Manchester, UK). Results: In all, 737 patients were recruited (AGAMENON-SEOM, n = 654; Manchester, n = 83). Median PFS and OS in the training cohort were 7.76 [95% confidence interval (CI), 7.13-8.25] and 14.0 months (95% CI, 13.0-14.9), respectively. Six covariates were significantly associated with OS: neutrophil-to-lymphocyte ratio, Eastern Cooperative Oncology Group performance status, Lauren subtype, HER2 expression, histological grade and tumour burden. The AGAMENON-HER2 model demonstrated adequate calibration and fair discriminatory ability with a c-index for corrected PFS/OS of 0.606 (95% CI, 0.578-0.636) and 0.623 (95% CI, 0.594-0.655), respectively. In the validation cohort, the model is well calibrated, with a c-index of 0.650 and 0.683 for PFS and OS, respectively. Conclusion: The AGAMENON-HER2 prognostic tool stratifies HER2-positive AGA patients receiving trastuzumab and chemotherapy according to their estimated survival endpoints.

Intensive care unit requirements in patients treated with immune checkpoint inhibitors.

OBJECTIVE: To determine the proportion of emergency patients treated with immune checkpoint inhibitors (ICIs) that require critical care admission and their requirements. DESIGN: Prospective case series. METHODS: Analysis of acutely unwell patients treated with ICIs attending a tertiary UK cancer hospital between May 2018 and May 2022. The primary outcome measure was the percentage of patients treated with ICI therapy requiring ICU admission. The secondary outcome measure was whether this need was driven by an immune-mediated toxicity. RESULTS: Eighteen (1.2%) patients of the 1561 acutely admitted patients treated with ICI therapy required an admission to ICU. Ten (55.5%) patients were admitted due to an immune-mediated toxicity; four due to pneumonitis and four due to myasthenia gravis. Seven of 10 survived their ICU admission with 6 surviving at least 6-month post-ICU discharge. CONCLUSIONS: Only a small minority of emergency admissions in patients treated with ICIs require admission to ICU. This series adds further evidence that patients with organ failure due to immune-mediated toxicity may achieve good outcomes from ICU admission.

Low-cost and clinically applicable copy number profiling using repeat DNA.

BACKGROUND: Somatic copy number alterations (SCNAs) are an important class of genomic alteration in cancer. They are frequently observed in cancer samples, with studies showing that, on average, SCNAs affect 34% of a cancer cell's genome. Furthermore, SCNAs have been shown to be major drivers of tumour development and have been associated with response to therapy and prognosis. Large-scale cancer genome studies suggest that tumours are driven by somatic copy number alterations (SCNAs) or single-nucleotide variants (SNVs). Despite the frequency of SCNAs and their clinical relevance, the use of genomics assays in the clinic is biased towards targeted gene panels, which identify SNVs but provide limited scope to detect SCNAs throughout the genome. There is a need for a comparably low-cost and simple method for high-resolution SCNA profiling. RESULTS: We present conliga, a fully probabilistic method that infers SCNA profiles from a low-cost, simple, and clinically-relevant assay (FAST-SeqS). When applied to 11 high-purity oesophageal adenocarcinoma samples, we obtain good agreement (Spearman's rank correlation coefficient, rs=0.94) between conliga's inferred SCNA profiles using FAST-SeqS data (approximately £14 per sample) and those inferred by ASCAT using high-coverage WGS (gold-standard). We find that conliga outperforms CNVkit (rs=0.89), also applied to FAST-SeqS data, and is comparable to QDNAseq (rs=0.96) applied to low-coverage WGS, which is approximately four-fold more expensive, more laborious and less clinically-relevant. By performing an in silico dilution series experiment, we find that conliga is particularly suited to detecting SCNAs in low tumour purity samples. At two million reads per sample, conliga is able to detect SCNAs in all nine samples at 3% tumour purity and as low as 0.5% purity in one sample. Crucially, we show that conliga's hidden state information can be used to decide when a sample is abnormal or normal, whereas CNVkit and QDNAseq cannot provide this critical information. CONCLUSIONS: We show that conliga provides high-resolution SCNA profiles using a convenient, low-cost assay. We believe conliga makes FAST-SeqS a more clinically valuable assay as well as a useful research tool, enabling inexpensive and fast copy number profiling of pre-malignant and cancer samples.

Symbiotic Modulation as a Driver of Niche Expansion of Coastal Plants in the San Juan Archipelago of Washington State.

Modern evolutionary theory and population genetics posit that adaptation and habitat expansion of plants result from processes exclusive to their genomes. Here, we present studies showing that plants can grow across complex habitat gradients by modulating symbiotic associations with Class 2 fungal endophytes. Endophyte analysis of three native (Leymus mollis, Distichlis spicata, and Salicornia pacifica) and one invasive (Spartina anglica) plant growing across adjacent microhabitats in the San Juan Archipelago altered associations with Class 2 fungal endophytes in response to soil salinity levels. At the microhabitat interfaces where the gradation of salinity varied, the plants were colonized by endophytes from both microhabitats. A reciprocal transplant study along a salt gradient demonstrated that Leymus mollis (dunegrass) required endophytes indigenous to each microhabitat for optimal fitness and/or survival. In contrast, when dunegrass and Grindelia integrifolia (gumweed) were found growing in low salinity, but high drought habitats, these plant species had their own unique dominant endophyte association regardless of geographic proximity and conferred drought but not high salt stress tolerance. Modulation of endophyte abundance occurred in planta based on the ability of the symbiont to confer tolerance to the stress imposed on plants. The ability of an endophyte to confer appropriate stress tolerance resulted in a significant increase of in planta fungal abundance. Conversely, the inability of an endophyte to confer stress tolerance resulted in a decrease of in planta fungal abundance. Our studies indicate that Class 2 fungal endophytes can provide a symbiotic mechanism for niche expansion and phenotypic plasticity across environmental gradients.

The occurrence and associated risk factors of brain metastases in well differentiated grade 1 and 2 bronchial neuroendocrine tumours: A single centre retrospective analysis of 280 patients.

Typical and atypical bronchial carcinoid account for around 2% of all neuroendocrine neoplasms of pulmonary origin. Fewer than 5% of patients with these cancers are thought to develop brain metastases, and hence routine intracranial imaging is not currently included in staging investigations. In this study, retrospective case note analysis was performed on 280 patients diagnosed with either typical carcinoid (TC) or atypical carcinoid (AC) at a large, single-site cancer centre. None of the 219 patients with TC developed brain metastases during the course of their disease, whereas seven of the 61 AC (11.5%) were found to have intracranial spread, four of which were present at the point of diagnosis. A Cox proportional hazard model showed that a Ki-67 expression ≥18%, patient age ≥65 years and disease stage at diagnosis were all independently and significantly associated with the development of brain metastases in AC. This study has found new evidence that the incidence of brain metastases in AC is significantly higher than previously thought. Of all the variables reviewed, Ki-67 expression was most strongly associated with the development of intracranial disease in AC and could be readily translated into clinical practice. Predictive factors such as age, disease stage and Ki-67 expression could be used to identify patients at particularly increased risk of brain metastases, who would benefit from early intracranial imaging. This could allow for earlier detection and treatment of metastases, with the potential to improve clinical outcomes and patient quality of life.

Rearrangement processes and structural variations show evidence of selection in oesophageal adenocarcinomas.

Oesophageal adenocarcinoma (OAC) provides an ideal case study to characterize large-scale rearrangements. Using whole genome short-read sequencing of 383 cases, for which 214 had matched whole transcriptomes, we observed structural variations (SV) with a predominance of deletions, tandem duplications and inter-chromosome junctions that could be identified as LINE-1 mobile element (ME) insertions. Complex clusters of rearrangements resembling breakage-fusion-bridge cycles or extrachromosomal circular DNA accounted for 22% of complex SVs affecting known oncogenes. Counting SV events affecting known driver genes substantially increased the recurrence rates of these drivers. After excluding fragile sites, we identified 51 candidate new drivers in genomic regions disrupted by SVs, including ETV5, KAT6B and CLTC. RUNX1 was the most recurrently altered gene (24%), with many deletions inactivating the RUNT domain but preserved the reading frame, suggesting an altered protein product. These findings underscore the importance of identification of SV events in OAC with implications for targeted therapies.

Transfer learning for data-efficient abdominal muscle segmentation with convolutional neural networks.

BACKGROUND: Skeletal muscle segmentation is an important procedure for assessing sarcopenia, an emerging imaging biomarker of patient frailty. Data annotation remains the bottleneck for training deep learning auto-segmentation models. PURPOSE: There is a need to define methodologies for applying models to different domains (e.g., anatomical regions or imaging modalities) without dramatically increasing data annotation. METHODS: To address this problem, we empirically evaluate the generalizability of various source tasks for transfer learning: natural image classification, natural image segmentation, unsupervised image reconstruction, and self-supervised jigsaw solving. Axial CT slices at L3 were extracted from PET-CT scans for 204 oesophago-gastric cancer patients and the skeletal muscle manually delineated by an expert. Features were transferred and segmentation models trained on subsets ( n = 5 , 10 , 25 , 50 , 75 , 100 , 125 $n=5,10,25,50,75,100,125$ ) of the manually annotated training set. Four-fold cross-validation was performed to evaluate model generalizability. Human-level performance was established by performing an inter-observer study consisting of ten trained radiographers. RESULTS: We find that accurate segmentation models can be trained on a fraction of the data required by current approaches. The Dice similarity coefficient and root mean square distance-to-agreement were calculated for each prediction and used to assess model performance. Models pre-trained on a segmentation task and fine-tuned on 10 images produce delineations that are comparable to those from trained observers and extract reliable measures of muscle health. CONCLUSIONS: Appropriate transfer learning can generate convolutional neural networks for abdominal muscle segmentation that achieve human-level performance while decreasing the required data by an order of magnitude, compared to previous methods ( n = 160 → 10 $n=160 \rightarrow 10$ ). This work enables the development of future models for assessing skeletal muscle at other anatomical sites where large annotated data sets are scarce and clinical needs are yet to be addressed.

Filter Inserts Impact Cloth Mask Performance against Nano- to Micro-Sized Particles.

The United States Centers for Disease Control and Prevention and World Health Organization recognize that wearing cloth face coverings can slow the transmission of respiratory diseases via source control. Adding a partial layer of material with a high filtration efficiency (FE, e.g., polypropylene sheets that meet the HEPA standard) as an insert can potentially provide additional personal protection; however, data on the necessary areal coverage are sparse. The relationship between insert area ratio (IAR) relative to fabric area, FE, differential pressure (ΔP, a surrogate for breathability), and quality factor (QF, a ratio including FE and ΔP) utilizing two fabrics (rayon and 100% cotton lightweight flannel) and three insert materials (HEPA vacuum bag, sterilization wrap and paper coffee filter) was investigated. The effect of inserts on particle flows mimicking human exhalation is semiquantitatively and qualitatively examined using flow visualization techniques. The following was found: (1) The relationship between FE, ΔP, and QF is complex, and a trade-off exists between personal protection from filtration during inhalation and source control from leakage during exhalation; (2) FE and ΔP of the composite covering increase with IAR, and the rate is dependent upon insert type; (3) improvements (decrements) in the QF of the composite assemblage require inserts with a higher (lower) QF than the fabric and larger differences yield greater gains (losses); (4) the increased ΔP from an insert results in increased leakage during exhalation; (5) to minimize leaks, ΔP must be as low as possible; and (6) small relative areas not covered by an insert (i.e., IAR slightly smaller than 1) strongly deteriorate the benefits of an insert similar to small leaks in a covering.

Hydration of Hydrophilic Cloth Face Masks Enhances the Filtration of Nanoparticles.

Under high humidity conditions that mimic respiration, the filtration efficiency (FE) of hydrophilic fabrics increases when challenged with hygroscopic nanoparticles, for example, respiratory droplets containing SARS-CoV-2. The FE and differential pressure (ΔP) of natural, synthetic, and blended fabrics were measured as a function of relative humidity (RH) for particles with mobility diameters between 50 and 825 nm. Fabrics were equilibrated at 99% RH, mimicking conditions experienced when worn as a face mask. The FE increased after equilibration at 99% RH by a relative percentage of 33 ± 12% for fabrics composed of two layers of 100% cotton when challenged by 303 nm-mobility-diameter NaCl aerosol. The FE for samples of synthetics and polyester/cotton blends was unchanged upon equilibration at 99% RH. Increases in FE for 100% cotton fabrics were a function of particle size with a relative increase of 63% at the largest measured particle size (825 nm). The experimental results are consistent with increased particle capture due to H2O uptake and growth as the particles traverse the fabric.

Tailoring Electrode-Electrolyte Interfaces in Lithium-Ion Batteries Using Molecularly Engineered Functional Polymers.

Electrode-electrolyte interfaces (EEIs) affect the rate capability, cycling stability, and thermal safety of lithium-ion batteries (LIBs). Designing stable EEIs with fast Li+ transport is crucial for developing advanced LIBs. Here, we study Li+ kinetics at EEIs tailored by three nanoscale polymer thin films via chemical vapor deposition (CVD) polymerization. Small binding energy with Li+ and the presence of sufficient binding sites for Li+ allow poly(3,4-ethylenedioxythiophene) (PEDOT) based artificial coatings to enable fast charging of LiCoO2. Operando synchrotron X-ray diffraction experiments suggest that the superior Li+ transport property in PEDOT further improves current homogeneity in the LiCoO2 electrode during cycling. PEDOT also forms chemical bonds with LiCoO2, which reduces Co dissolution and inhibits electrolyte decomposition. As a result, the LiCoO2 4.5 V cycle life tested at C/2 increases over 1700% after PEDOT coating. In comparison, the other two polymer coatings show undesirable effects on LiCoO2 performance. These insights provide us with rules for selecting/designing polymers to engineer EEIs in advanced LIBs.

Filtration Efficiencies of Nanoscale Aerosol by Cloth Mask Materials Used to Slow the Spread of SARS-CoV-2.

Filtration efficiency (FE), differential pressure (ΔP), quality factor (QF), and construction parameters were measured for 32 cloth materials (14 cotton, 1 wool, 9 synthetic, 4 synthetic blends, and 4 synthetic/cotton blends) used in cloth masks intended for protection from the SARS-CoV-2 virus (diameter 100 ± 10 nm). Seven polypropylene-based fiber filter materials were also measured including surgical masks and N95 respirators. Additional measurements were performed on both multilayered and mixed-material samples of natural, synthetic, or natural-synthetic blends to mimic cloth mask construction methods. Materials were microimaged and tested against size selected NaCl aerosol with particle mobility diameters between 50 and 825 nm. Three of the top five best performing samples were woven 100% cotton with high to moderate yarn counts, and the other two were woven synthetics of moderate yarn counts. In contrast to recently published studies, samples utilizing mixed materials did not exhibit a significant difference in the measured FE when compared to the product of the individual FE for the components. The FE and ΔP increased monotonically with the number of cloth layers for a lightweight flannel, suggesting that multilayered cloth masks may offer increased protection from nanometer-sized aerosol with a maximum FE dictated by breathability (i.e., ΔP).

Genomic evidence supports a clonal diaspora model for metastases of esophageal adenocarcinoma.

The poor outcomes in esophageal adenocarcinoma (EAC) prompted us to interrogate the pattern and timing of metastatic spread. Whole-genome sequencing and phylogenetic analysis of 388 samples across 18 individuals with EAC showed, in 90% of patients, that multiple subclones from the primary tumor spread very rapidly from the primary site to form multiple metastases, including lymph nodes and distant tissues-a mode of dissemination that we term 'clonal diaspora'. Metastatic subclones at autopsy were present in tissue and blood samples from earlier time points. These findings have implications for our understanding and clinical evaluation of EAC.

Early recognition of anorexia through patient-generated assessment predicts survival in patients with oesophagogastric cancer.

Cancer cachexia is common in patients with oesophagogastric cancer (OG) and is linked to overall survival (OS). One of the key components of cachexia is anorexia; it is not known whether anorexia impacts on OS and there is no method of routine screening in current practice. Diagnosis relies on patients describing the symptoms, clinicians diagnosing anorexia and acting upon it. Patients with oesophageal/gastroesophageal junction or gastric cancer were assessed using the Functional Assessment of Anorexia Cachexia Therapy Anorexia/Cachexia Subscale (FAACT A/CS). FAACT A/CS includes 12 questions validated previously to diagnose anorexia in patients with cancer. Of the 182 patients included, 69% scored ≤37/48 and were considered to be anorexic; FAACT A/CS was a better predictor of OS in metastatic patients than body mass index or weight loss in the six months prior to cancer diagnosis. The median OS of patients with FAACT A/CS scores of >37 was longer than patients with scores of ≤37 (19.3 months vs 6.7 months, Hazard Ratio [HR] 2.9, 95% Confidence Interval [CI] 1.4-6.0, p<0.0001). Patients with performance status (PS) 0-2 and FAACT A/CS >37 had substantially longer OS than those with PS 0-2 and FAACT A/CS ≤37 (18.7 months vs 7.9 months, HR 2.5 (95% CI 1.2-5.1, P<0.0001). The FAACT A/CS questionnaire allows clinicians to identify patients with anorexia who may benefit from early nutrition interventions. Importantly, this is the first study to show the association between anorexia and survival in patients with metastatic OG cancers. This will form the basis of future interventional studies to improve patient outcomes.

Properties of Pertechnic Acid.

Dilute aqueous pertechnic acid has long been known as strong monoprotic acid that behaves as a simple pertechnetate ion in aqueous solution. As pertechnic acid concentrates by evaporation, it becomes yellow and then dark red, and dark-red crystalline material may ultimately be obtained. We show that as pertechnic acid concentrates, at least three compounds are formed: a yellow viscous liquid, a colorless (not red) crystalline solid, and a small amount of an intensely colored red-purple compound. The colorless crystalline compound melts at 118 °C and can be melted and recrystallized several times with little decomposition. The red-purple compound is apparently not stable at room temperature and quickly decomposes if it is isolated. UV-vis spectra show that Beer's law does not hold as pertechnic acid concentrates by evaporation. We report densities, 99Tc nuclear magnetic resonance spectra, and ultraviolet-visible absorption spectra for highly pure aqueous pertechnic acid (accompanied by the other technetium compounds that form) ranging from 1 to 14 M in technetium concentration.

Pandemic fluoroquinolone resistant Escherichia coli clone ST1193 emerged via simultaneous homologous recombinations in 11 gene loci.

Global growth in antibiotic resistance is a major social problem. A high level of resistance to fluoroquinolones requires the concurrent presence of at least 3 mutations in the target proteins-2 in DNA gyrase (GyrA) and 1 in topoisomerase IV (ParC), which occur in a stepwise manner. In the Escherichia coli chromosome, the gyrA and parC loci are positioned about 1 Mb away from each other. Here we show that the 3 fluoroquinolone resistance mutations are tightly associated genetically in naturally occurring strains. In the latest pandemic uropathogenic and multidrug-resistant E. coli clonal group ST1193, the mutant variants of gyrA and parC were acquired not by a typical gradual, stepwise evolution but all at once. This happened as part of 11 simultaneous homologous recombination events involving 2 phylogenetically distant strains of E. coli, from an uropathogenic clonal complex ST14 and fluoroquinolone-resistant ST10. The gene exchanges swapped regions between 0.5 and 139 Kb in length (183 Kb total) spread along 976 Kb of chromosomal DNA around and between gyrA and parC loci. As a result, all 3 fluoroquinolone resistance mutations in GyrA and ParC have simultaneously appeared in ST1193. Based on molecular clock estimates, this potentially happened as recently as <12 y ago. Thus, naturally occurring homologous recombination events between 2 strains can involve numerous chromosomal gene locations simultaneously, resulting in the transfer of distant but tightly associated genetic mutations and emergence of a both highly pathogenic and antibiotic-resistant strain with a rapid global spread capability.