Elongation and branching of stem channels produced by positive streamers in long air gaps.

The elongation and branching of long positive spark discharges in the laboratory and in lightning have been attributed to the formation of thermalized channels inside a diffuse, glow-like streamer section at the leader head. It is experimentally shown here that the structured morphology of streamers produce low-density stem channels that elongate and branch well before a new leader channel section is formed. These non-thermalized stems are also shown to develop ahead of a developing leader channel. These findings are based on high-speed photography and Schlieren imaging used to visualize both the morphology of streamer filaments and stem channels. Numerical analysis is also performed to estimate the axial temperature and density of the stem channels. A stem-driven mechanism for the propagation and branching of positive long air gap discharges is proposed and discussed based on the presence of not-yet thermalized, low density channels formed by streamer ensembles at the leader head.

Prevalence and risk analysis of mobile colistin resistance and extended-spectrum ß-lactamase genes carriage in pet dogs and their owners: a population based cross-sectional study.

Mobile colistin resistance gene mcr-1 and extended-spectrum ß-lactamase gene bla CTX-M are highly prevalent in human - and pet-derived bacteria. Isolation of identical strains of mcr-1-positive Escherichia coli (MCRPEC) or bla CTX-M-positive E. coli (CTX-MPEC) from pets and humans highlighted the potential for co-colonization of antibiotic-resistant bacteria which can be a risk for dissemination of resistance genes. In this study, the prevalence of mcr-1 and bla CTX-M carriage from rectal swabs in 299 families (dogs and their owners) were 2.7 and 5.3%, respectively. We identified a significant association of mcr-1 carriage between dogs and their owners. Whilst antibiotic use in the previous three months was associated with bla CTX-M carriage in dogs. Only one instance of dog and owner carrying identical CTX-MPEC was observed. Although the prevalence of identical strains in one family is rare, the huge number of dog ownership worldwide suggest that this threat should not be underestimated.

Abundance of tigecycline resistance genes and association with antibiotic residues in Chinese livestock farms.

The discovery of plasmid-mediated tet(X) variants and efflux pump gene tmexCD1-toprJ1 conferring bacteria resistance to tigecycline has compromised glycylcycline as the last line of defense against infection, which poses serious threat to public health. Herein, real-time quantitative PCR was used to detect the abundance of seven tigecycline resistance genes (TRGs), including six tet(X) variants and tmexCD1-toprJ1, and insertion sequences ISCR2 and IS26. Then, the concentrations of nine antibiotics were quantified in fecal samples collected from 157 livestock farms in four Chinese provinces. TRGs, especially tet(X4), tmexCD1-toprJ1, and insertion sequences ISCR2 and IS26, were more abundant in chicken feces than in pig and cattle feces, suggesting the greater risk for the propagation of TRGs in chicken feces. Positive correlations (ρ = 0.3741-0.8275, P < 0.0001) between ISCR2/IS26 and TRGs (except tet(X1)) further demonstrated that ISCR2 mediates the transfer of tet(X3), tet(X4), and tet(X5) and that IS26 plays a certain role for the mobilization of tet(X4) and tmexCD1-toprJ1. Tetracyclines had no positive correlation with the abundance of TRGs (except tet(X1)), meanwhile florfenicol and tiamulin were positively correlated with TRGs. However, further research is needed to confirm whether or not florfenicol and tiamulin are potential driving factors of TRG accumulation.

Prevalence, etiology, and economic impact of clinical mastitis on large dairy farms in China.

This study investigated the continuous monthly prevalence of bovine clinical mastitis (CM) and the distribution of causative pathogens among 36,619 CM milk samples from large dairy farms across seven Chinese provinces from 2015 to 2017 using data from routine CM recording systems. Based on treatment period and cost per cow, withdrawal period, daily milk production, and milk value data from each farm in 2017, we calculated the economic impact of CM at the farm level with 2578-9044 lactating cows per farm. Results showed a wide variation in monthly prevalence of CM (0.6 %-18.2 %) among the seven farms over the study period, indicating regional and temporal differences in the occurrence of CM in China. Enterobacteriaceae were the predominant pathogens across all farms from six provinces except Shandong, in which the Streptococcus spp. was the most prevalent. However, the distribution of various Enterobacteriaceae species differed among farms, and Streptococcus species distribution was strongly associated (Pearson's coefficient, 68.4 %) with location. Monthly economic losses associated with CM showed clear variation, ranging from 12,000-76,000 USD/farm/month. Sensitivity analysis showed that economic loss at the farm level was most sensitive to variation in the prevalence of CM, followed by antibiotic treatment period and daily milk production per cow. To our knowledge, this is the longest running study of CM and the first estimation of its economic impacts in China. Our findings highlight the considerable costs associated with mastitis, and indicate that preventive measures and regional and timely treatment of CM are needed.

Co-existence of two novel phosphoethanolamine transferase gene variants in Aeromonas jandaei from retail fish.

Two novel phosphoethanolamine transferase genes, eptAv7 and eptAv3, were identified in the chromosome of an Aeromonas jandaei isolate from retail fish. The variants showed 79.9% and 80.0% amino acid identity to MCR-7.1 and MCR-3.1, respectively, and increased colistin resistance 128- to 256-fold in Aeromonas salmonicida. The two variants with no mobile genetic element in the flanking regions were also observed in other Aeromonas species. This finding supports the view that Aeromonas is a reservoir for MCR-3 and MCR-7 mobile colistin resistance.

Inter-host Transmission of Carbapenemase-Producing Escherichia coli among Humans and Backyard Animals.

BACKGROUND: The rapidly increasing dissemination of carbapenem-resistant Enterobacteriaceae (CRE) in both humans and animals poses a global threat to public health. However, the transmission of CRE between humans and animals has not yet been well studied. OBJECTIVES: We investigated the prevalence, risk factors, and drivers of CRE transmission between humans and their backyard animals in rural China. METHODS: We conducted a comprehensive sampling strategy in 12 villages in Shandong, China. Using the household [residents and their backyard animals (farm and companion animals)] as a single surveillance unit, we assessed the prevalence of CRE at the household level and examined the factors associated with CRE carriage through a detailed questionnaire. Genetic relationships among human- and animal-derived CRE were assessed using whole-genome sequencing-based molecular methods. RESULTS: A total of 88 New Delhi metallo-ß-lactamases-type carbapenem-resistant Escherichia coli (NDM-EC), including 17 from humans, 44 from pigs, 12 from chickens, 1 from cattle, and 2 from dogs, were isolated from 65 of the 746 households examined. The remaining 12 NDM-EC were from flies in the immediate backyard environment. The NDM-EC colonization in households was significantly associated with a) the number of species of backyard animals raised/kept in the same household, and b) the use of human and/or animal feces as fertilizer. Discriminant analysis of principal components (DAPC) revealed that a large proportion of the core genomes of the NDM-EC belonged to strains from hosts other than their own, and several human isolates shared closely related core single-nucleotide polymorphisms and blaNDM genetic contexts with isolates from backyard animals. CONCLUSIONS: To our knowledge, we are the first to report evidence of direct transmission of NDM-EC between humans and animals. Given the rise of NDM-EC in community and hospital infections, combating NDM-EC transmission in backyard farm systems is needed. https://doi.org/10.1289/EHP5251.

Integrated aquaculture contributes to the transfer of mcr-1 between animals and humans via the aquaculture supply chain.

BACKGROUND: Since its discovery in 2015, the mobile colistin resistance gene mcr-1 has been reported in bacteria from >50 countries. Although aquaculture-associated bacteria may act as a significant reservoir for colistin resistance, systematic investigations of mcr-1 in the aquaculture supply chain are scarce. OBJECTIVES: We investigated the presence of colistin resistance determinants in the aquaculture supply chain in south China and determined their characteristics and relationships. METHODS: A total of 250 samples were collected from a duck-fish integrated fishery, slaughter house, and market in Guangdong Province, China, in July 2017. Colistin-resistant bacteria were isolated on colistin-supplemented CHROMagar Orientation plates, and the species were identified by matrix-assisted laser desorption/ionization time-of-flight assay. The presence of mcr genes was confirmed by polymerase chain reaction analysis. We examined the minimum inhibitory concentrations (MICs) of 16 antimicrobial agents against the isolates using agar diffusion and broth microdilution methods. Whole-genome sequencing (WGS) was used to explore the molecular characteristics and relationships of mcr-1-positive Escherichia coli (MCRPEC). RESULTS: Overall, 143 (57.2%) colistin-resistant bacteria were isolated, of which, 56 (22.4%, including 54 Escherichia coli and two Klebsiella pneumoniae) and four Aeromonas species were positive for mcr-1 and mcr-3, respectively. The animal-derived MCRPEC were significantly more prevalent in integrated fishery samples (40.0%) than those in market (4.8%, P<0.01) samples but not in slaughter house (28.0%, P=0.164). All MCRPEC were highly resistant to ampicillin, tetracycline, and compound sulfamethoxazole (>90%) but were susceptible to carbapenems and tigecycline. WGS analysis suggested that mcr-1 was mainly contained on plasmids, including IncHI2 (29.6%), IncI2 (27.8%), IncX4 (14.8%), and IncP (11.1%). Genomic analysis suggested mcr-1 transmission via the aquatic food chain. CONCLUSIONS: MCRPEC were highly prevalent in the aquaculture supply chain, with the isolates showing resistance to most antibiotics. The data suggested mcr-1 could be transferred to humans via the aquatic food chain. Taking the "One Health" perspective, aquaculture should be incorporated into systematic surveillance programs with animal, human, and environmental monitoring.

Characterization of multiresistance gene cfr(C) variants in Campylobacter from China.

OBJECTIVES: To investigate the occurrence, the genetic environment and the functionality of novel variants of the MDR gene cfr(C) in Campylobacter from China. METHODS: A total of 370 Campylobacter isolates of porcine and chicken origin collected from three regions of China in 2015 were screened for cfr(C) by PCR. The phenotypes and genotypes of cfr(C)-positive isolates were investigated by antimicrobial susceptibility testing, PFGE, MLST, S1-PFGE, Southern blotting and WGS. Quantitative RT-PCR was used to compare the expression levels of the cfr(C) variants in their original isolate and clone constructs in Campylobacter jejuni NCTC 11168. RESULTS: Four (1.1%) porcine Campylobacter coli isolates were positive for cfr(C). They failed to show elevated MICs of phenicols. The deduced Cfr(C) sequences identified exhibited 2-6 amino acid changes compared with the original Cfr(C) reported in the USA. Cloning of the cfr(C) variant genes into C. jejuni NCTC 11168 resulted in ≥32-fold increases in the MICs of phenicols, indicating that the cfr(C) variant genes are functional. The cfr(C)-carrying isolates belonged to three genotypes and WGS analysis revealed the cfr(C) genes were chromosomally located in MDR genomic islands, which contained multiple antibiotic resistance genes of Gram-positive origin. CONCLUSIONS: This study identified chromosomal cfr(C) genes in C. coli isolates from China. They appeared functionally dormant in the original isolates but were fully functional when cloned and expressed in C. jejuni. The cfr(C) genes were co-transferred with other antibiotic resistance genes, possibly from Gram-positive bacteria. These findings reveal new insights into the function and transmission of cfr(C) in Campylobacter.

A New Denoising Method for UHF PD Signals Using Adaptive VMD and SSA-Based Shrinkage Method.

Noise suppression is one of the key issues for the partial discharge (PD) ultra-high frequency (UHF) method to detect and diagnose the insulation defect of high voltage electrical equipment. However, most existing denoising algorithms are unable to reduce various noises simultaneously. Meanwhile, these methods pay little attention to the feature preservation. To solve this problem, a new denoising method for UHF PD signals is proposed. Firstly, an automatic selection method of mode number for the variational mode decomposition (VMD) is designed to decompose the original signal into a series of band limited intrinsic mode functions (BLIMFs). Then, a kurtosis-based judgement rule is employed to select the effective BLIMFs (eBLIMFs). Next, a singular spectrum analysis (SSA)-based thresholding technique is presented to suppress the residual white noise in each eBLIMF, and the final denoised signal is synthesized by these denoised eBLIMFs. To verify the performance of our method, UHF PD data are collected from the computer simulation, laboratory experiment and a field test, respectively. Particularly, two new evaluation indices are designed for the laboratorial and field data, which consider both the noise suppression and feature preservation. The effectiveness of the proposed approach and its superiority over some traditional methods is demonstrated through these case studies.

Association of colistin residues and manure treatment with the abundance of mcr-1 gene in swine feedlots.

BACKGROUND: The extensive use of colistin in swine production may have contributed to the recent emergence of corresponding mobile resistance gene mcr-1. The use of colistin as a feed additive was banned in China in April 2017. OBJECTIVES: To examine the occurrence of colistin and dissemination of mcr-1 in swine feedlots before and after the colistin ban and effects of different manure treatments. METHODS: Environmental samples were collected from swine feedlots before (December 2016) and after (December 2017) the colistin ban. Colistin concentrations were determined by ultra-high performance liquid chromatography coupled to tandem mass spectrometry. The prevalence of mcr-1 were determined by quantitative PCR analysis, while bacterial community composition was investigated by 16S rRNA sequencing. RESULTS: In 2016, colistin was detected in feed and fresh manure samples at 67 mg/kg and 17 mg/kg, respectively, but was absent from all samples in 2017. In 2016, the relative abundance of mcr-1 in fresh manure was lower than that in solid samples after natural drying, while a higher relative abundance was detected in fresh manure samples compared with biogas slurry samples. A strong correlation between colistin concentration and relative abundance of mcr-1 was observed in fresh manure. The samples collected in 2017 showed a lower relative abundance of mcr-1 compared with those collected in 2016. Bacterial community analysis showed that the abundance of Enterobacteriaceae, which act as a vehicle and reservoir of mcr-1, increased with natural dying but decreased with anaerobic digestion. CONCLUSIONS: The presence of colistin exerts direct selection pressure for the accumulation of mcr-1 in manure, while the ban on colistin likely halted the dissemination of mcr-1 on pig farms. Anaerobic digestion is an effective waste treatment process for removing mcr-1, which might be mainly driven by the shift in bacterial community structure.

Genetic environment of colistin resistance genes mcr-1 and mcr-3 in Escherichia coli from one pig farm in China.

The aim of this study was to assess the presence of mobile colistin resistance in bacteria isolated from the swine production environment and to analyze the genomic environment of the new colistin resistance gene mcr-3. Anal swabs and environmental samples were collected from a commercial pig farm. Direct sample testing (DST) for mcr genes and isolation of colistin-resistant isolates was performed. The mcr-3-positive isolates were subjected to whole genome sequencing (WGS). Transferability and genomic location analyses of mcr-3 gene were performed using conjugation and S1 nuclease-PFGE with Southern blotting assays, respectively. The antimicrobial susceptibility profiles of the mcr-carrying isolates were determined using the agar dilution method. A total of 65 samples were collected. The DST rates of mcr-1 (64.6%, 42/65) and mcr-3 (40.0%, 26/65) were considerably higher than the rates of mcr-1-positive E. coli (49.2%, 32/65) and mcr-3-positive E. coli (7.7%, 5/65) isolated from these samples, respectively. The five mcr-3-positive isolates were derived from different sources (pig, fly and soil) and four of the five isolates were also positive for mcr-1. The mcr-3 genes were located on IncP-1 plasmids in three isolates or IncHI2 plasmids in two isolates. Several mobile elements, including IS4321, ΔTnAs2 or ISKpn40, were identified in the flanking regions of mcr-3 in the E. coli isolates. In conclusion, the mobile colistin resistance genes mcr-1 and mcr-3 are prevalent in the monitored pig farm and its surrounding environment. Due to their location on broad-host range IncP-1 plasmids and their proximity to different IS sequences, mcr-3 gene might have excellent opportunities for transmission.

Research on ultra-fast vacuum mechanical switch driven by repulsive force actuator.

In order to meet the fast operation demands of DC circuit breakers, a high-speed vacuum mechanical switch (VMS) driven by a repulsive force actuator is focused. To improve the drive speed and energy conversion efficiency (ECE) of the actuators, the dynamic characteristics of the double sided coil repulsive force actuators are investigated, and two generalized optimization design methods focusing on the aspect ratio of the driving coils (defined as ARF) and the electrical parameters (defined as EF) are developed. FEM simulation models' simulation and tests of VMS prototypes are conducted to verify the optimization methods. Results prove that the ARF method could improve the ECE of a VMS from 1.05% to 7.55%, and EF method could improve ECE of the same VMS from 1.05% to 6.61%, the combination of ARF and EF could improve the value of VMS's ECE to 10.50%, thus proving the validity and accuracy of the optimization methods.

Digital time-resolved optical measurement of discharge currents in long air gaps.

Shortcomings in the dynamic range and the frequency bandwidth of current diagnostic methods mean that measurement of the time-resolved discharge current in a long air gap discharge is still a serious problem. This work presents data from a novel discharge current sensor that takes the parameters required to determine the accuracy of the current measurement into account. The design of a coaxial current sensor with ±0.7% accuracy and a bandwidth of 75 MHz is presented. A digital optical fiber transmission system with a bandwidth that exceeds 100 MHz is used to transmit the signal. To demonstrate the efficiency of the whole system, experiments using a rod-plane discharge geometry with 2 m and 4 m air gap lengths are performed to analyze the measured current data in comparison with that taken from synchronized high-speed photographs. The results demonstrate that the investigated experimental set-up improves substantially the understanding of the fundamental mechanisms of long air gap discharges.

On-line estimation of laser-drilled hole depth using a machine vision method.

The paper presents a novel method for monitoring and estimating the depth of a laser-drilled hole using machine vision. Through on-line image acquisition and analysis in laser machining processes, we could simultaneously obtain correlations between the machining processes and analyzed images. Based on the machine vision method, the depths of laser-machined holes could be estimated in real time. Therefore, a low cost on-line inspection system is developed to increase productivity. All of the processing work was performed in air under standard atmospheric conditions and gas assist was used. A correlation between the cumulative size of the laser-induced plasma region and the depth of the hole is presented. The result indicates that the estimated depths of the laser-drilled holes were a linear function of the cumulative plasma size, with a high degree of confidence. This research provides a novel machine vision-based method for estimating the depths of laser-drilled holes in real time.

[Development of a nitric oxide supply system for respiratory distress treatments].

College of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan,430074 Inhaled nitric oxide (INO) is increasingly being used in medical treatments of high blood pressure, acute respiratory distress syndrome (ARDS) and some diseases related with lungs. In this paper, in view of the problems in the current supply systems of NO for the treatments of respiratory failure, an INO system for clinical applications is designed based on experimental studies. Its continuous trial run shows that the outlet concentration of NO can be supplied constantly, and the ratio of NO2/NO is about 2.7%. So it satisfies the clinical requirements (NO2/NO<5%). In comparison of the conventional NO supply systems, this system has significant advantages, it can work so long as the air and the electricity exist.