The emergence of Neisseria gonorrhoeae strains with decreased susceptibility to cephalosporins and azithromycin (AZM) resistance (AZM(r)) represents a public health threat of untreatable gonorrhea infections. Genomic epidemiology through whole-genome sequencing was used to describe the emergence, dissemination, and spread of AZM(r) strains. The genomes of 213 AZM(r) and 23 AZM-susceptible N. gonorrhoeae isolates collected in Canada from 1989 to 2014 were sequenced. Core single nucleotide polymorphism (SNP) phylogenomic analysis resolved 246 isolates into 13 lineages. High-level AZM(r) (MICs ≥ 256 μg/ml) was found in 5 phylogenetically diverse isolates, all of which possessed the A2059G mutation (Escherichia coli numbering) in all four 23S rRNA alleles. One isolate with high-level AZM(r) collected in 2009 concurrently had decreased susceptibility to ceftriaxone (MIC = 0.125 μg/ml). An increase in the number of 23S rRNA alleles with the C2611T mutations (E. coli numbering) conferred low to moderate levels of AZM(r) (MICs = 2 to 4 and 8 to 32 μg/ml, respectively). Low-level AZM(r) was also associated with mtrR promoter mutations, including the -35A deletion and the presence of Neisseria meningitidis-like sequences. Geographic and temporal phylogenetic clustering indicates that emergent AZM(r) strains arise independently and can then rapidly expand clonally in a region through local sexual networks.

A large-scale, whole-genome comparison of Canadian Neisseria gonorrhoeae isolates with high-level cephalosporin MICs was used to demonstrate a genomic epidemiology approach to investigate strain relatedness and dynamics. Although current typing methods have been very successful in tracing short-chain transmission of gonorrheal disease, investigating the temporal evolutionary relationships and geographical dissemination of highly clonal lineages requires enhanced resolution only available through whole-genome sequencing (WGS). Phylogenomic cluster analysis grouped 169 Canadian strains into 12 distinct clades. While some N. gonorrhoeae multiantigen sequence types (NG-MAST) agreed with specific phylogenomic clades or subclades, other sequence types (ST) and closely related groups of ST were widely distributed among clades. Decreased susceptibility to extended-spectrum cephalosporins (ESC-DS) emerged among a group of diverse strains in Canada during the 1990s with a variety of nonmosaic penA alleles, followed in 2000/2001 with the penA mosaic X allele and then in 2007 with ST1407 strains with the penA mosaic XXXIV allele. Five genetically distinct ESC-DS lineages were associated with penA mosaic X, XXXV, and XXXIV alleles and nonmosaic XII and XIII alleles. ESC-DS with coresistance to azithromycin was observed in 5 strains with 23S rRNA C2599T or A2143G mutations. As the costs associated with WGS decline and analysis tools are streamlined, WGS can provide a more thorough understanding of strain dynamics, facilitate epidemiological studies to better resolve social networks, and improve surveillance to optimize treatment for gonorrheal infections. N eisseria gonorrhoeae is a Gram-negative diplococcus bacterium that causes gonorrhea infections. Gonorrhea is the second most reported bacterial sexually transmitted infection (STI) in Canada, with reported cases increasing from 15.5 per 100,000 in 1997 to 36.2 per 100,000 in 2012 (1), and approximately 106 million cases are estimated annually worldwide (2). N. gonorrhoeae bacteria have developed resistance against sulfonamides, penicillins, tetracyclines, and fluoroquinolones (3, 4), and current treatment options now include third-generation extended-spectrum cephalosporins (ESC), namely, cefixime (CFM) and ceftriaxone (CRO) (5). MIC creep has seen the modal MIC values rise between 2001 and 2010 in Canada from 0.016 g/ml to 0.125 g/ml and 0.063 g/ml for CFM and CRO, respectively (6). These results coincide with recent clinical reports of treatment failures to primarily CFM monotherapy in Canada (7,8) and additional global reports of high-level CRO MICs in isolates from Japan and Europe (9-13). Furthermore, isolates with decreased susceptibility to cephalosporins and coresistance to azithromycin (AZM), a recommended cotherapy (5), have recently been identified in Canada (14).Decreased susceptibility to extended-spectrum cephalosporins (ESC-DS) and resistance to AZM have been attributed to several molecular mechanisms. The primary mechanism for ESC-DS is modification of the ...

Random networks comprised of millimeter-long multi-walled carbon nanotubes (CNTs) have shown unique microstructure change mechanisms under uniaxial strain. These networks can be modified into highly aligned microstructures from strain-induced plastic deformation. Applying a treatment consisting of an uncured resin as a load transfer enhancement medium leads to a dramatically increased degree of alignment and final mechanical properties of the CNT networks. The structural evolution of the CNT networks includes different modes: de-bundling, elongation to reduce waviness, sliding friction, and packing for self-assembly into large bundles. The high ductility of the treated networks, which allows the network to achieve high degrees of strain-induced alignment is mainly because the extra high aspect ratios of the individual CNTand their bundles as well as enhanced load transfer. High aspect ratio causes high degrees of entanglement and locking points between the nanotubes in the random network, which are critical to provide adequate nanotube to nanotube load transfer for ductile deformation and lead to substantially increased CNT alignment during mechanical stretching. The classical strain strengthening mechanisms used in metals and polymers such as strain hardening and crystallization of long molecular chains are discussed and compared to CNT network deformation mechanisms. The CNT network strain hardening parameter n value is as high as 0.65, over three times that of annealed low-carbon steel and more than four times of polycarbonate plastics. Strength coefficient K values for the CNT network also show high values up to roughly 450 MPa, comparable to that of annealed magnesium alloys. The results show how the high degree of alignment of CNT networks and strain strengthening can be achieved through simple uniaxial strain and load transfer medium.

No abstract

Here we describe the synthesis and characterization of peptide conjugated cellulose and nanocellulose materials as sensors for fluorescent detection of human neutrophil elastase (HNE). The cellulose sensor surfaces selected are filter paper (FP) and print cloth (PC) fabric, which are composed of processed cotton fibers. The nanocellulose based sensors have transducer surfaces comprised of cellulose nanocrystals (wCNC) and microfibrillated cellulose (MFC) derived from wood that are fabricated as wood nanocellulose composites (wNCCs) consisting of blended quantities of nanocrystalline and MFC at 66/33 and 50/50 ratios. These ratios were selected to examine the effect of significantly different CNC loadings had on surface area and peptide uptake. The fluorescent peptide HNE substrate, n-succinyl-Ala-Pro-Ala-4-amido-7-methylcoumarin (Pep) was attached to both cellulosic and nanocellulosic matrices and conjugated peptide analogs were confirmed by mass spectrometry (MS) and infrared (IR). The nanocellulose biosensors wCNCPep (3c) and wNCC-Pep (4c, 66/33 and 5c, 50/50) have higher levels of peptide incorporation than the cellulosic biosensors FP-Pep (1c) and PC-Pep (2c). The range of incorporation for the cellulosic sensors is 7-25 lg/mg and for the nanocellulose sensors 30-80 lg/mg. The degree of substitution of peptide was found to be in the order of approximate number of peptides per 200 anhydroglucose residues, 1 in PC-Pep (2c), 2 in FP-Pep (1c), 4 in wNCC-Pep (5c, 50/50), 6 in wNCC-Pep (4c, 66/33), and 12 in wCNC-Pep (3c). The specific surface areas of the sensors ranged from 0.016 to 261 m 2 g -1 and correlated with degree of substitution of peptide on the cellulosic and nanocellulosic surfaces. Of the cellulose and nanocellulose biosensors, the wCNC-Pep (3c) has the highest level of peptide incorporation and the highest specific surface area, which makes it the preferred sensor matrix for human neutrophil elastase.

This paper reports on a study of carbon nanotube (CNT) thin film, or buckypaper (BP), integrated into carbon fiber (CF) prepreg composites to create hybrid composite materials with high CNT content. The autoclave process of manufacturing hybrid composite laminates was investigated to gain an understanding of nano/micro dual-scale resin flow characteristics. The study found that resin bleeding along the through-thickness direction was inhibited due to extra-low permeability and high resin absorbing capacity of the BP. Resin matrix-impregnated BP layers were much thicker than dry pristine BP due to high resin absorbency and swelling effects. The BP/unidirectional carbon fiber (UD-CF) hybrid composites with local fiber volume fraction of 61.46 vol% in CF ply and local CNT volume fraction of 26.57 vol% in BP layer, had a tensile strength of 2519 AE 101 MPa and modulus of 149 AE 18 GPa. The dramatic improvements in both in-plane and through-thickness electrical conductivities demonstrate potential for both structural and multifunctional applications of the resultant hybrid composites.

Carbon nanotube thin films or 'buckypapers' show potential for various applications including electrodes for energy devices, nanoscale filtration devices and composite materials. This paper reports on the study of through-thickness permeability of different buckypaper materials. The infiltration behaviours of different liquids into four types of buckypaper were investigated. Infiltration of the liquids into buckypaper was found to follow Darcy's law, except in the case of epoxy resin solution permeation into SWNT buckypaper. The results revealed that the permeability of SWNT buckypaper was of the order of 10(-19) m(2), which is about two orders of magnitude lower than the 10(-17) m(2) permeability for the MWNT buckypaper. The factors of wider pores, higher porosity and less surface area appear to contribute to a higher permeability, which is consistent with Darcy's law and the Kozeny-Carman model. The Kozeny constants of buckypapers correlated well with the tortuosity of their flow paths and nanoscale pore size. The polarity of working fluids did not show an impact on the permeability. Solutions with molecular size near the size of the nanopores in the buckypaper led to lower permeability due to the occurrence of pore blockage. In addition, a threshold pressure existed for liquid to infiltrate into nanoscale pores in buckypapers, which does not exist in fibre reinforcement preforms.

The emergence of Neisseria gonorrhoeae strains that are resistant to azithromycin and extended-spectrum cephalosporins represents a public health threat, that of untreatable gonorrhea infections. Multivariate regression modeling was used to determine the contributions of molecular antimicrobial resistance determinants to the overall antimicrobial MICs for ceftriaxone, cefixime, azithromycin, tetracycline, ciprofloxacin, and penicillin. A training data set consisting of 1,280 N. gonorrhoeae strains was used to generate regression equations which were then applied to validation data sets of Canadian (n = 1,095) and international (n = 431) strains. The predicted MICs for extended-spectrum cephalosporins (ceftriaxone and cefixime) were fully explained by 5 amino acid substitutions in PenA, A311V, A501P/T/V, N513Y, A517G, and G543S; the presence of a disrupted mtrR promoter; and the PorB G120 and PonA L421P mutations. The correlation of predicted MICs within one doubling dilution to phenotypically determined MICs of the Canadian validation data set was 95.0% for ceftriaxone, 95.6% for cefixime, 91.4% for azithromycin, 98.2% for tetracycline, 90.4% for ciprofloxacin, and 92.3% for penicillin, with an overall sensitivity of 99.9% and specificity of 97.1%. The correlations of predicted MIC values to the phenotypically determined MICs were similar to those from phenotype MIC-only comparison studies. The ability to acquire detailed antimicrobial resistance information directly from molecular data will facilitate the transition to whole-genome sequencing analysis from phenotypic testing and can fill the surveillance gap in an era of increased reliance on nucleic acid assay testing (NAAT) diagnostics to better monitor the dynamics of N. gonorrhoeae.